Infectious Diseases 11% Flashcards
1
Q
What is contained within a bacterial culture transport medium?
A
Designed to maintain bacterial viability
- typically consists of a small amount of agar
- reagents that maintain pH
- a colorimetric pH indicator that indicate if oxidation has taken place
- Specific factors that maintain the viability of certain pathogens
2
Q
List three examples of acid-fast stains
A
1) Ziehl-Neelsen stain
2) Fite’s stain
3) Kinyoun stain
3
Q
What does MALDI-TOF stand for?
A
Matrix-assisted laser desorption ionization time-of-flight mass spectrometry
4
Q
What is an MIC?
A
Minimum inhibitory concentration
- lowest concentration of an antimicrobial drug that inhibits visible growth of an organism over a define incubation period, usually 18-24 hours
- Determined using dilution methods which involve exposing the organism to twofold dilutions of an antimicrobial drug
- usually reported in ug/mL
- The lower the MIC, the more potent an antibiotic is at inhibiting the organism
5
Q
List 3 different dilution methods used to evaluate bacterial MIC’s
A
- Broth macrodilution
- Broth microdilution
- Agar dilution
6
Q
Broth microdilution
A
- Twofold dilutions of antimicrobials are made in a broth medium in a microtiter plate
- Each well is inoculated with a standard amount of bacteria
- A pellet of bacteria settles to the bottom of the each well when growth fails to be inhibited by the concentration of the antimicrobial in each well.
7
Q
List two diffusion methods to determine MIC
A
1) Gradient diffusion, also known as E-Test
2) Disc diffusion (i.e. Kirby-Bauer)
8
Q
What is gradient diffusion (aka an E-test)
A
- Placement of a plastic strip that has a gradient of antimicrobial on one side and an MIC interpretative scal eon the other side
- Agar plate is inoculated with the pathogen such that subsequent growth forms a “lawn”
- Strips result in elliptical zone of growth inhibition around the strip
- MIC read at the point of intersection where the ellipse meets the strip.
9
Q
What is kirby-bauer disk diffusion?
A
- Entire surface of agar is incoulated with pathogen
- Drug-impregnanted filter papers of varying concentrations applied to the surface of the agar plate
- Drug diffuses from filter paper into agar, further away from the agar paper the lower the [ ] is of the drug
- Filter papers result in a “zone of inhibition”
- Zone diameters are interpreted as susceptible, resistant and intermediate based on CLSI guidelines
10
Q
What is a “breakpoint”?
A
- Organisms classified on a bacterial sensitivity report as susceptable, intermediate or resistant based on a predicted in vivo situaiton
- Susceptable isolated have antimicrobial drug concentrations that are usually achievable in blood and tissues using normal drug dosages
- Intermediate isolates have MIC’s that approach the usually attainable blood and tissue levels for which response rates may be lowe than those of susceptable isolates unless the drug concentrates in the tissue of interest ( i.e. amoxicillin in urine
- Resistant isolates are predicted to grown in the face of the usually achievable drug concetrations in blood and tissue
- Breakpoint concentrations are not reported to clinicians
- Breakpoints decided upon and reviewed by CLSI
- Breakpoints are decided based on knowledge of MIC distributions and resistance mechanisms for each organism-drug combination, clinical response rates in humans and animals, how the drug is distributed and metabolized by the body, whether the drug is concentration or time dependant,
- Breakpoints are established for antimicrobial drug concentrations in the blood stream and are based on specific dosage regime for the antimicrobial tested; dosage regime selected for by the standards agency involved
11
Q
How is the minimum bacterialcidal concentration (MBC) determined?
A
- Minimum concentration of an antimicrobial drug that is bactericidal
- Determined by subculturing broth dilutions that inhibit growth of a bacterial organism (i.e. those at or above MIC)
- Lowest broth dilution of antimicrobial that prevents growth of the organism on the agar plate
12
Q
What is the mutant prevention concentration?
A
- The lowest antimicrobial drug concentration required to block the growth of the least susceptible bacterial cell in high density bacterial populations
- It is the MIC of the most resistant bacterial strain in a mixed bacterial population
- Concentrations between MIC and MPC allow selective amplification of resistant mutants (i.e. mutant selection window, or “danger zone”)
- Estimated using the standard agar dilution method used to estimate MIC but with a larger inoculum so as to include resistant subpopulations of bacteria
- Administration of higher doses of antimicrobial drugs that exceed MPC increases chance of toxicity to the patient but offsets chance for resistant organisms even though infection may be cured with lower dosage
- Not routinely performed in veterinary diagnostic laboratories
13
Q
Papillomavirus
A
- Small, noneveloped viruses with icosahedral symmetry and double-stranded circular DNA genome
- lack a lipid envelope
- very host-specific; however cross infection of horses by bovine papillomavirus 1 and 2 has been reported
- Must penetrate the basal layers in order to cause an infection through a break in the skin.
14
Q
What papillomaviruses have been associated with canine pigmented viral plaques?
A
CdPV4 ( especially in pugs ), CdPV3, CdPV5, CdPV7
15
Q
List the typical histologic findings of papillomas?
A
- Papillomatous hyperplasia of the epidermis with extensive orthokeratotic hyperkeratosis
- Clumped keratohyalin granules within the strartum spinosis
- Koilocytes (keratinocytes with swollen, clear cytoplasm and pyknotic (shrunken) nucleus)
- Clear cells (keratinocytes with swollen, blue-gray cytoplasm and enlarged nuclei)
- Intranuclear inclusion bodies
16
Q
What are intracytoplasmic pseudoinclusions seen in feline viral plaques?
A
- Appear fibrillar in the stratum spinosum and compact in the stratums granulosum
- Composed of re-arranged keratin filaments
17
Q
Pythium insidiosum
A
- Aquatic pathogen belonging to the class Oomycetes
- Differ from true fungi in producing motile, flagellate zoospores and having cell walls that contain cellulose and beta-glucan but not chitin
- Ergosterol is not an important part of the cell membrane
- sterol auxotrophs: incorporate sterols from the environment and do not produce them
- closely related to prototheca
18
Q
What is the infective stage of Pythium insidiosum?
A
Biflagellate aquatic zoospore that encyst in G.I. tract and skin
19
Q
What signalment of dogs and lifestyle more commonly develope pythiosis?
A
Young, large-breed male dogs, especially in outdoor working breeds such as Labrador retrievers .
Infected dogs are oftentimes immunocompetent, otherwise healthy and have recurrent exposure to warm, freshwater habitats
20
Q
What is the common distribution of cutaneous pythiosis in dogs?
A
extremities, tailhead, ventral neck, perineum, medial thighs
21
Q
What special stains highlight Pythium insidiosum
A
Gomori methenamine silver stain (GMS) but NOT periodic acid-Schiff stain (PAS)
22
Q
List 9 cutaneous manifestations of Feline leukemia virus
A
1) Chronic/recurrent gingivitis
2) Chronic/recurrent pyoderma (folliculitis, abscess, paronychia)
3) Poor wound healing
4) Seborrhea
5) Exfoliative dermatitis
6) Generalized pruritus
7) Increased susceptibility to dermatophytosis, demodicosis, Malassezia dermatitits, bowenoid in situ carcinomas
8) Cutaneous horns
9) Giant cell dermatosis
23
Q
What are two clinical syndromes that have been associated with FeLV infection
A
1) Cutaneous horns
2) Giant cell dermatosis
24
Q
What IHC stain can be used to demonstrate the presence of FeLV antigen?
A
gp70
25
What is a characteristic histologic feature of Giant cell dermatosis?
Syncytial-type giant cell formation in the epidermis and outer root sheath of hair follicles to the level of the isthmus; keratinocytes within and around the giant cells are often apoptotic; involved skin shows positive gp70 staining but non-lesional skin does not.
26
What are 6 cutaneous manifestations of Feline immunodeficiency virus?
1) Chronic or recurrent oral disease (gingivitis, periodontal disease, stomatitis)
2) Chronic/recurrent abscesses
3) Chronic bacterial infections of the skin/ears
4) Increased frequency of infection with Cryptococcus neoformans, Candida albicans or Microsporum canis
5) Increased frequency of demodicosis
6) Increased risk of bowenoid in situ lesions and multiple mast cell tumors
27
What is the vector for feline poxvirus infections?
Rodents are the natural hosts; cats get infections from wounds inflicted while hunting rodents; actually transmit a cowpox virus which belong to the orthopoxvirus family; Endemic in Europe and Western Asia.
28
What are the clinical features of feline poxvirus (i.e. "cowpox")?
Single ulcerated nodule on the head, neck or foreleg which can become secondarily infected with bacteria; secondary skin lesions consist of small epidermal nodules that enlarge over 3-5 days and ulcerate, forming craters and crusts; some cats develop oral vesiculation or ulceration; lesions heal slowly over 4-5 weeks and permanent scarring can occur.
29
What are a defining feature of keratinocytes infected with poxvirus?
Eosinophilic intracytoplasmic inclusion bodies are found within keratinocytes of the epidermis, hair follicles and sebaceous glands.
30
Exotic felids (especially cheetahs) are at high risk of developing rapidly developing progressive and fatal pneumonia during the viremic period of which virus?
Feline poxvirus (i.e. cowpox)
31
What are X cutaneous manifestations of feline infectious peritonitis
Causes by certain strains of feline coronavirus; can cause ulcerative lesions around the head and neck; histopathologic tests show changes typical of a superficial vasculitis and viral antigens can be demonstrated in blood vessel walls by immunohistochemical technique; one cat develop fragility skin syndrome but may be from the catabolic state
32
List the cutaneous signs that can occur in canine distemper
A paramyxovirus
- Widespread impetigo (due to general debility)
- "Hard-pad" disease resulting in nasal and footpad hyperkeratosis
33
What are defining histologic features seen in cutaneous manifestations of canine distemper virus
1) Marked orthokeratosis and parakeratotic hyperkeratosis
2) Acidophilic cytoplasmic inclusion bodies seen in keratinocytes
3) Occasional multinucleate syncytial giant cells may be seen in the epidermis.
34
What is the causative agent of contagious viral pustular dermatitis?
Orf, contagious echythma - a parapoxvirus that commonly infects small ruminants
35
Intense, maniacal upper-body pruritus is a cardinal feature of 52% of dogs infected with which virus?
Pseudorabies, an alpha herpesvirus
36
Describe the clinical features of dermatitis associated with feline herpesvirus-1 infection in cats.
- Double stranded DNA virus with a glycoprotein-lipid envelope; little strain variation and only one serotype has been associated with clinical disease in cats
- May or may not have active or historical ocular or respiratory signs
- Cats can also develop oral ulcers
- Crusted lesions involve the nasal planum, bridge of the nose, periocular skin. When crusts removed, exposed skin is inflamed and ulcerated.
- Similar crusted and ulcerative lesions can be found elsewhere on the body.
- The inflammation is typically characterized by a predominance of eosinophils, but neutrophils can predominate in some cases.
37
What are some clinical differentials for crusting and ulcerative skin lesions involving the nasal planum, bridge of the nose and periocular skin?
Feline herpes viral dermatitis, mosquito bite hypersensitivity, eosinophilic plaques, calicivirus-associated dermatitis, FeLV dermatitis, drug reaction, erythema multiforme, pemphigus foliaceus and SLE
38
Describe the histologic features of feline herpesviral dermatitis
Ulcerative and often necrotic dermatitis; suppurative folliculitis and furunculosis can be seen; Demodex cat may be visible in follicular lumen; perivascular to interstitial mixed inflammatory dermatitis with many eosinophils. In the surface and follicular epithelium, multinucleate giant cells can be seen and amphophilic intranuclear inclusion bodies can be seen in the giant cells and other keratinocytes. A unique feature of this disease is necrosis of the EPITRICHIAL SWEAT GLANDS.
39
What are some triggers of feline herpes viral dermatitis?
Stress and corticosteroid use
40
What is virulent systemic feline calicivirus?
A severe, hemorrhagic and highly virulent biotype of FCV that can results in:
- Facial and paw edema
- Pyrexia
- Ocular and nasal discharge
- Icterus
- Bloody diarrhea
- Oral ulcers as well as ulcers and crusting of the nose, lips, pinnae, periocular region and distal limbs.
- Mortality of 30-50% its death attributable to bacterial sepsis / DIC
- pneumonia, hepatopathy, pancreatitis, pericardities
41
What are clinical signs seen with feline calicivirus
A small, undeveloped, single-stranded RNA virus belonging to the genus Vesivirus; many different strains exist
- most commonly causes oral vesicles and ulcers, depression, pyrexia, sneezing, conjunctivitis with ocular/nasal discharge
- Ulcers commonly found on tongue, may be present on lips, gingival mucosa and nose
- Lymphoplasmacytic gingivitis and stomatitis with chronicity.
- Some strains have affinity for joints, resulting in lameness
42
What is "transient febrile limping syndrome"
Infection with a strain of feline calicivirus that has an affinity for the joints, resulting in a lameness that resolved after a few days
43
List six different syndromes that have been associated with papillomavirus infections in dogs.
Each of the following 6 syndromes are distinguished by anatomic distribution, histologic features, IHC, PCR and/or in situ DNa hybridization
1) Oral papillomatosis
2) Venereal papillomas
3) Exophytic cutaneous papillomas
4) Cutaneous inverted papillomas
5) Multiple papillomas of the footpad
6) Canine pigmented viral plaques
44
What are papillomaviruses?
small double-stranded DNA viruses; typically species specific and belong to the Papovavirus; infect keratinocytes in the stratum basale, undergo genome replication in the spinous and granular layers, and release new infectious virus in kertainized squames
45
What are histologic features of papillomaviral infections?
- Increased mitotic rate resulting in acanthosis and hyperkeratosis
- Formation of koilocytes in the upper stratum spinosum
- Giant keratohyalin granules in the stratum granulosusm
- Pale basophilic intranuclear inclusion bodies may be found in the upper stratum spinosum or stratum granulosum
46
What is a koilocyte?
Keratinocytes with clear cytoplasm and pyknotic nuclear +/- presence of pale, basophilic intranuclear inclusion bodies in the upper stratum spinosum or stratum granulosum
47
What breeds are at increased risk for developing pigmented viral plaques?
Pugs, Miniature Schnauzers (STRONG BREED PREDISPOSITION FOR THESE), possibly Boston Terriers and French Bulldogs
48
Why is 5-fluorouracil contraindicated in cats?
Neurotoxicity
49
What four syndromes have been associated with papillomaviruses in cats?
1) Feline cutaneous papillomas
2) Feline cutaneous fibropapillomas (also referred to as feline Sarcoids)
3) Feline viral plaques
4) Feline bowenoid in situ carcinomas and squamous cell carcinomas
50
What disease in small animals is associated with spending time outdoors and known exposure to cattle?`
Feline cutaneous fibropapillomas (i.e. feline sarcoids)
| - majority of lesions are PCR positive for papillomavirus with a strong similarity to bovine papilomavirus 1.
51
When papillomavirus and/or demodex is diagnosed in an older patient, what should this prompt?
An investigation for an immunosuppressed state:
- Dogs: hypercortisolemia, hypothyroidism, cancer, chemotherapeutic/corticosteroids
- Cats: FeLV, FIV, FIP, chronic corticosteroid use
52
What skin disease does Feline sarcoma virus cause?
cutaneous fibrosarcomas in young cats, also associated with the development of other neoplasias (lymphosarcoma, liposarcoma, melanoma, hemangioma, multiple cutaneous horns)
53
What are cutaneous manifestations of infection with Rocky mountain spotted fever (a rickettsial disease caused by Rickettsia rickettsi)?
Cutaneous lesions are attributable to a necrotizing vasculitis; only 20% of dogs infected develop cutaneous signs
- erythema
- petechiation
- edema (of the distal limbs may be the earliest sign)
- necrosis and ulceration of the oral, ocular and genital mucous membranes as well as of the skin of the nose, pinnae, ventrum, scrotum, distal limbs and feet.
- Painful and swollen epididymis of male dogs.
- Systemic signs: lethargy, fever, anorexia, peripheral lymphadenopathy, signs of neurologic dysfunction.
54
What ticks transmit Rocky Mountain Spotted Fever?
Causes by the rickettsial agent Rickettsia rickettsi
- Dermacentor andersoni (Rocky mountain wood tick)
- Dermacentor variabilis (American dog tick)
55
What tick primarily transmits Ehrilichiosis (caused by the gram-negative obligate intracellular bacteria Ehrlichia canis?)
Rhipicephalus sanguineus (Brown dog tick)
56
Are the clinical features of ehrlichiosis?
- fever, weight loss, depression, lethargy, anorexia
- Hematologic and clotting abnormalities (anemia, thrombocytopenia, leucopenia, hyperproteinemia, hyperglobulinemia), vasculitis, monoarthopathy, polyarthropathy
- Morulae in leuckocytes
57
What are cutaneous manifestations of toxoplasmosis (causes by the obligate intracellular coccidian parasite, Toxoplasma gondii)?
skin lesions include pyogranulomatous or necrotizing dermatitis and vasculitis; nodular pyogranulomatous dermatitis has been reported in dogs and cats developing disseminated toxoplasmosis.
58
What are the definitive hosts for a) toxoplasma gondii and b) neospora caninum
a) Cats
| b) Domestic dogs and wild coyotes
59
When tachyzoites are found via histopathology or FNA from a nodular skin lesion, what are the two top differentials and how do you differentiate them?
Toxoplasma gondii and Neospora gondii
| - immunohistochemical, ultrastructural or PCR studies
60
List the intermediate hosts for Neospora caninum
Cattle, deer, dogs, goats, horses and sheep
61
What are the clinical signs of neosporosis?
Neurologic and muscular signs predominate; pneumonia, hepatitis, myocarditis or dermatitis.
62
What kind of skin disease can neosporosis produce?
Uncommonly reported, but can result in widespread draining nodules. One dog had rapidly spreading ulcerative dermatitis of the eyelids, neck, thorax and perineum.
63
What is the signalment and lifestyle of animals that develop neosporosis?
- Medium to large purebred dogs
| - Feral, rural or free-roaming dogs and those fed raw meat
64
Where can leishmania be found in the a) old world and b) new world?
a) The Mediterranean basin, Portugal, France, Germany, Switzerland, Netherland
b) South and Central America, Texas, Oklahoma, Ohio, Michian and Alabama
65
What transmits Leishmania to humans and animals?
Bloodsucking sandflies of the genus "Lutzomyia" in the New World and Phlebotomus in the Old World.
66
Are are reservoir hosts for Leishmania?
Domestic and wild dogs, rodents, and other wild mammals
67
What is pathomechanism behind tissue damage due to leishmania?
Granulomatous inflammation and immune-complex deposition
68
What signalment and lifestyle of dogs are at increased risks?
- Possible predisposition for German shepherds and boxers
- younger than 3 years old and between 8-10 years old
- Rural animals, especially those that spend the night outdoors
- Foxhounds in the USA
69
What percentage of animals with visceral leishmaniasis have cutaneous signs?
> 80%
70
What are the cutaneous lesions seen in leishmaniassis
- exfoliative scaling with silver-white asbestos lookign scale; can be generalized but often most pronounced on head, pinnae and extremities
- Nasodigital hyperkeratosis
- Periocular alopecia (i.e. lunettes)
- Ulcerative dermatitis
- Onychogryphosis and paronychia
- sterile pustular dermatitis
- Nasal depigmentation with erosion and ulceration
- Nodular dermatitis
- Secondary pyoderma occurs often
- Demodicosis
71
What are the systemic signs of illness and extracutnaoeus physical exam findings seen in Leishmania?
- decreased endurance, weight loss, somnolence
- Generalized lymphadenopathy, hepatosplenomegaly
- Muscle wasting, cachexia, intermittent fever, keratoconjunctivitus, epistaxis, lameness, PU/PD and other signs from progressive renal failure
- Can results in Leishmania-induced cell-mediated immunodeficiency
- Many clinical signs overlap with SLE
72
As immunodeficiency is not a pre-requisite for leishmaniasis, resistance or susceptibility to clinical leishmaniasis is based on what?
Whether an animal mounts a Th1 or Th2 response with Th1 conferring resistance and Th2 conferring susceptibility
- IL-2 and TNF-a play a protective role
73
What are clinical differentials for cutaneous leishmaniasis?
Pemphigus foliaceus, SLE, zinc-responsive dermatosis, necrolytic migratory erythema, sebaceous adenitis and cutaneous lymphoma.
74
How is leishmaniasis diagnosed?
Finding the organism on cytologic or histopathologic evaluation of tissues; PCR assays; cultures; xenodiagnosis; or through demonstration of anti-leishmania antibodies or positive skin test reaction.
75
What can you see on cytology of Leishmania infected animals?
Amastigotes within macrophages in affected tissues
76
What stain can be used to highlight amastigotes?
Giemsa
77
What are histologic features of leishmaniasis?
- Organisms can be challenging to identify on histo
- Lymphoplasmacytic, pyogranulomatous or granulomatous inflammation with vasculitis
- Prominent orthokeratotic and parakeratotic hyperkeratosis; inflammation predominated by macrophages
- There have been 9 histologic patterns identified: granulomatous perifolliculitis, interstitial dermatitis, superficial and deep perivascular dermatitis, lichenoid interface dermatitis, nodular dermatitis, lobular panniculitis, suppurative folliculitis, intraepidermal pustular dermatitis.
78
What do leishmania organisms look like?
Can be found intracellularly or extracellularly; round to oval 2-4 micrometer in size, contain a round basophilic nucleus and a small rodlike kinetoplast
79
What tissue is most likely to identify leishmania?
Bone marrow and lymph nodes, skin, conjunctivia, buffy coat, whole peripherally obtained blood.
80
What is xenodiagnosis as it pertains to leishmaniasis?
Allowing laboratory-bred phlebotomine vectors to feed on the dog and later examining the flies for the presence of promastigotes in their gut.
81
A) What test for leishmaniasis was recommended by the World Organization for Animal Health as the reference serologic method? B) False positive test results can occur due to cross reactivity with what pathogen?
A) Immunofluorescent antibody test - IFAT
| B) Trypanosoma cruzi
82
As leishmaniasis is considered an incurable disease, what are the goals of treatment?
Decrease parasite load, treat organ damage, and improve an animal's immune response against the parasite.
83
What is the most commonly used drug for the treatment of leishmaniasis in dogs and humans?
N-methyl-glucamine (i.e. Meglumine) antimoniate - 100 mg/kg SQ once daily for 4 weeks
- can cause injection site pain, fever, anorexia, and diarrhea, transient elevations in ALT and amylase
- Reduces parasite load, increases specific IgG antibody responses, improves cell-mediated immunologic responses to the parasite.
84
What FDA-approved drug is commonly prescribed in addition to meglumine for the treatment of leishmaniasis?
Allopurinol; 10 mg/kg PO q 12 hours
85
Aside from meglumine and allopurinol, what other drugs have been used for treatment of leishmanisis?
- Aminosidine (aka paromomycin), FDA-approved aminoglycoside
- Marbofloxacin: synthetic third generation fluoroquinolone;
- Amphotericin B, miltefosine, pentamidine, domperidone, spiramicin, metronidazole, ketoconazole
86
What measures can be recommended to minimize at-risk dogs from contracting leishmaniasis?
- Keep indoors during vector feeding periods (i.e. 1 hour before sunset to 1 hour after dawn)
- Install fine mesh around kennel
- Topical repellants using Permethrin +/- imidacloprid; deltamethin impregnated collars
- Pyriprole and metaflumizone have no effect against sandflies
87
What are some examples of antimicrobial peptides
Defensins, cathelicidins, adrenomedullin
88
What factors influence the cutaneous microbiota?
pH, heat, salinity, moisture, albumin level and fatty acid level
89
What are normal residents of the surface of dog-skin?
- Micrococcus spp.
- Coagulase negative staph (especially S. epidermidis, St. xylosus)
- alpha-hemolytic streptococci
- Clostridium spp.
- Propionibacterium acnes
- Acinetobacter spp.
- Various gram-negative aerobes
90
What are the normal residents of canine hair shafts?
- Micrococcus spp.
- Gram-negative aerobes
- Bacillus spp.
- Staphylococcus pseudintermedius
91
What are normal residents of the canine hair follicle?
- Micrococcus spp.
- Propionibacterium acnes
- Streptococci
- Bacillus spp.
- S. pseudintermedius
92
What are the resident microbiota of cat skin?
- Micrococcus spp.
- Coagulase-negative staphylococci (especially S. simulans and S. felis)
- alpha-hemolytic streptococci
- Acinetobacter spp.
- Coagulase positive staphylococci (S. aureus, S. pseudintermedius)
93
What are transient microbiota of the skin of dogs?
- Escherichia coli
- Proteus mirabilis
- Corynebacterium spp.
- Bacillus spp.
- Pseudomonas spp.
- Coagulase-positive staphylococci
94
What are transient microbiota of the skin of cats?
- beta-hemolytic streptococci
- E. coli
- P. mirabilis
- Pseudomonas spp.
- Alcaligenes spp.
- Bacillus spp.
95
What are some substances that are produced by Staphylococcus pseudintermedius?
- Enterotoxin A, B, C, D
- Toxic shock toxin
- Exfoliative toxin
- Leucotoxins
- Protein A
- Hemolysins
- Slime
96
What are common oral microbiota of the cat that can be found in cat bite abscesses?
- Pasteurella multocida
- Beta-hemolytic streptococci
- Corynebacterium spp.
- Actinomyces spp.
- Bacteroides spp.
- Fusobacterium spp.
97
What are some factors that could be attributed for the increase in number of skin infections in dogs relative to humans?
- Thinner stratum corneum
- Paucity of intercellular lipids
- Lack of a lipid follicular plug
- A higher pH
98
What are common antibacterial agents included in topical therapies?
- Chlorhexidine
- Povidone-iodine
- Ethyl lactate
- Benzoyl Peroxide
- Fusidic acid, mupirocin, bacitracin, silver sulfadiazine
99
What are better antibiotic options for intracellular bacteria?
- Fluoroquinolones
- Lincosamides
- Chloramphenicol
100
List immunomodulatory properties of a) macrolides, b) trimethoprim, c) fluoroquinolones
a) Macrolides inhibit leukocyte chemotaxis, IL-2 and lymphocyte blastogenesis
b) Trimethoprim inhibits leukocyte chemotaxis
c) Fluoroquinolones inhibit IL-1 and leukotrienes and inhibit granulomatous inflammation
101
A) What is impetigo?
B) List the clinical forms of impetigo?
C) What predisposed an animal to each form of impetigo?
A) A superficial pyoderma characterized by non-follicular, subcorneal pustules typically affecting the glabrous skin of the axillae and ventral abdomen; a benign problem that typically heals spontaneously; topical therapy will hasten resolution.
B) Bullous impetigo and "puppy pyoderma", or impetigo of young dogs
C) Impetigo in young dogs - typically causes by a coagulase-positive staphylococci; affects young dogs before puberty; can occur for no apparent reason, or secondary to parasitism, viral infections, a dirty environment or poor nutrition; Bullous impetigo - seen more often in older dogs, associated with immunosuppression from hypercortisolism, diabetes mellitus, hypothyroidism or other debilitating diseases; other bacter (E. coli, Pseudomonas spp) can be present
102
A) What breeds are predisposed to mucocutaneous pyoderma
B) What are the clinical features of mucocutaneous pyoderma?
C) What body sites are involved in MCP?
D) How is it treated?
A) German shepherd dogs and German Shepherd crosses
B) Symmetric swelling and erythema of the lips, especially at the commissures, crusting, fissuring, erosion, exudation beneath crusts; depigmentation can occur with chronic cases ; Lesions are tender and dog will rub areas and resent examination/palpation of the area.
C) Lips, eyelids, nares, vulva, prepuce or anus
D) Antibacterial topical shampoo to remove crustings, consider mupirocin ointment; rarely oral antibiotics are required
103
What are the three most common etiologic agents in canine folliculitis?
1) Staphylococci
2) Dermatophytosis
3) Demodicosis
104
What are interesting presentations of superficial pyoderma in a) bulldogs and b) dalmations
A) Infected areas are hairless and hyperkeratotic with minimal inflammation
B) Bronzing of hairs in areas of folliculitis
105
What are some clinical differentials for VCLE?
- Erythema multiforme
- Systemic lupus erythematosus
- Pemphigus vulgaris
106
What are histologic differentials for VCLE?
- Erythema multiforme (tends to feature apoptosis in a more transepidermal pattern rather then predominately in the basilar or suprabasilar pattern)
- Dermatomyositis (although VCLE doesn't feature ischemic changes to the collagen or hair follicles )
- Other forms of cutaneous lupus erythematosus (DLE has more intense lichenoid band dermal inflammation and less severe basal cell degeneration; does not feature sebaceous or follicular atrophy seen in ECLE)
- Lupoid-like drug reactions
107
What is erythema ab igne?
Alopecia, mottled erythematous scaly or crusted macules and plaques
108
What is erythema ab igne?
Alopecia, mottled erythematous scaly or crusted macules and plaques that give rase to hyperpigmentation with chronicity; lesions are linear and intersecting lattice-like hyperpigmentation with alopecia is highly characteristic
- occurs secondary to chronic exposure to conductive heat sources; sources include heating pads, heated kennel mats, electric blankets, plant warmers, metal heat register covers, infrared lamps, sun-heated driveways, cable television boxes, electronic devices commonly left on.
109
What are histologic features of erythema ab igne?
- Cell poor interface reaction featuring mild apoptosis of basal cells, subepidermal bubbling vacuoulation and vesiculation just beneath the basement membrane zone
- Presence of dysplastic keratinocytes with karyomegaly or the presence of red spaghetti of walder differentiate erythema ab igne from other interface reactions; if these are lacking, lesions may look like ischemic dermatopathy or thymoma-associated exfoliative dermatitis of cats
- Presence of eosinophilic, wavy elastin fibrils in the superficial dermis (Called "red spaghetti of Walder") that stand out with Verhoeff-van Gieson stain for elastin
- Variable laminar fibrosis in the superficial dermis
- Dermal collagen may have a smudged or faded appearance
- Superficial to deep dermal edema and mucin
- Increased acid mucopolysaccharides visualized by alcian blue staining
- subtle vasculopathy
- Atrophic, telogenized or faded hair follicles
- Moderate acanthosis with hyperkeratosis
- Pigmentary incontinence
110
What kind of bacteria is Dermatophilus?
An actinomycete; can cause dermatophilosis, also referred to as cutaneous streptotrichosis.
- A gram positive coccus
111
Dermatophilosis in small animals
- Caused by Dermatophilus congolensis
- Gram-positive coccus, rare cause of pustular dermatitis in small animals
- Clinical disease commonly occurs after rainy season
- Moisture released infectious zoospores; essential initiating factor; affected animals usually have skin defects/inflammation/trauma to skin to allow infection
- Typically a secondary invader
- Motie organisms eventually form flagellate zoospores that are highly resistant to drying and can survive in crusts for years
- Germinate to produce a filament that invades the living epidermis and proliferates within it
- Most common in moist, warm climates
- erythematous papules and pustules w/ crusts thicken and expand; isolated circular lesions may coalesce into larger areas
- Exudative, purulent dermaitits
112
What is the typical susceptibility profile of Dermatophilosis?
Susceptible: ampicillin, cephalosporin, cloxacillin, lincomycin, tetracycline, tylosin, high dose penicillin
Resistent: Erythromycin, novobiocin, sulfonamides, polymyxin B and low doses of penicillin
113
What are 4 bacteria that can be isolated from canine deep pyoderma?
- Staphylococcus pseudintermedius
- E. coli
- Proteus spp.
- Pseudomonas spp.
114
Furunculosis of any type is usually associated with a XXX? When this is not present, what is implied?
- Tissue eosinophilia
| - Immunosuppression, especially that due to concurrent glucocorticoid therapy or demodicosis
115
How is pyotraumatic dermatitis different from pyotraumatic folliculitis and furunculosis
- Pyotraumatic dermatitis is a superficial ulcerated inflammatory process without a significant bacterial component that oftentimes responds to cleaning and corticosteroids: occur in the pants region.
- Pyotraumatic folliculitis - superficial ulceration, deep suppurative and necrotizing folliculitis and occassional furunculosis; the lesions is thickened, plaquelike and surrounded by satellite papules and pustules; common in cheek and neck regions; more common in Golden retrievers and St. Bernards, Labradors and Newfoundlands
116
What breeds are predisposed to nasal folliculitis and furunculosis (i.e. nasal pyoderma?) What is the proposed aetiology
- German shepherd dogs, bull terriers, collie, pointer and other hunting-type dogs (i.e. dolicocephalic breeds)
- Cause unknown, though to be from rooting behavior or trauma
- Can look like pemphigus, lupus erythematosus, drug eruptions, dermatomyositis, nasal eosinophilic folliculitis and furunculosis, demodicosis, dermatophytosis, sterile pyogranuloma/granuloma syndrome, early juvenile cellulitis
117
What breeds are predisposed to muzzle folliculitis and furunculosis? What is the proposed pathophysiology?
- Almost exclusively a disorder of short-coated breeds including the Doberman pinscher, Boxer, English bulldog, Great Dane, Mastiff, rottweiler, German short haired pointer
- Suspect local trauma sustained to short bristly hair coat; it is a pressure point and weight bearing surface; can be traumatized during play time, especially in young puppies
118
What are causes of parasitic pododermatitis?
- Demodex
- Pelodera strongyloides
- Ancylostoma spp.
- Uncinaria stenocephala
- Ticks and chiggers
119
What should you consider if a single foot is affected by pododermatitis?
- A foreign body
- Local injury
- Neoplasia
120
What are some causes of pododermatitis?
- Trauma
- Clipper burn
- Fungal infections (malassezia, dermatophytosis, candidiasis, mycetoma, phaeohyphomycosis, sporotrichosis, blastomycosis, cryptococcosis)
- Parasites
- Psychogenic causes
- Steile pyogranulomas in dogs with short bristly hair coats
- Inherited or acquired immunodeficiency (i.e from demodicosis or hypothyroidism)
- Idiopathic
- Allergic
- Hypothyroidism
- Anatomy and abnormal weight bearing
121
What diagnostics should be performed in cases of pododermatitis?
- Multiple trichograms
- Skin scrapings
- Exudative cytology
- Fungal culture
- Representative skin biopsy
- Consider CBC, thyroid and adrenal function testing.
122
What is the active ingredient in Epsom salts? When do we use them?
Magnesium sulfate
| Exudative pododermatitis, 10-15 minute soaks twice daily
123
What are some treatment recommendations for pododermatitis?
- Oral antibiotics
- Magenesium sulfate soaks
- Avoid walking on rough terrain and use of booties
124
What are some treatment recommendations for pododermatitis?
- Oral antibiotics
- Magenesium sulfate soaks
- Avoid walking on rough terrain and use of booties
- Surgical debridement and fusion podoplasty in severe cases
125
What are some underlying causes for german shepherd deep pyoderma?
- Allergic skin disease
- Hypothyroidism
- Cell-mediated immunodeficiency (increased CD8+ and decreased numbers of CD4+ and CD21+ lymphocytes in circulation)
- Exaggerated response tissue response to Staphylococcal bacteria characterized by an inappropriate release of cytokines and other inflammatory mediators
- Because they do not experience infections or organ systems and infections do not occur until middle age, they must have some degree of immunocompetence; with an insult to their skin, they decompensate and experience a disproportionately severe pyoderma
- Some dogs decompensate for no known reason suggestive immunodeficiency can worsen with advancing age.
126
What are the clinical features of german shepherd deep pyoderma?
- affects middle-aged german shepherds almost exclusively
- Most lesions are pruritic; lesions typically involve the rump, back, ventral abdomen, and thighs; some animals develop more generalizing lesions.
- Lesions typically are initially follicular in origin
- Can develop weight loss, poor appetite, pyrexia; peripheral lymphadenopathy is common
127
MAKE SURE YOU EVALUATE THYROID LEVELS IN GERMAN SHEPHERD DEEP PYODERMA
Some people believe enrofloxacin is the antibiotic of choice as it concentrated within inflammatory cells and is unimpeded by granulomatous inflammation, fibrosis and purulent debris; enrofloxacin also has antiinflammatory properties
128
What are two gas-producing bacteria that can cause anaerobic cellulitis?
Clostridium and Bacteroides; both can cause crepitus in infected tissue
129
What are clinical features of anaerobic cellulitis?
- Usually occurs following bite wounds, traumatic puncture wounds, foreign body introduction but can also occur as a sequela to surgery, trauma, burns, or malignancy
- Rapid progression, poor demarcation, massive tissue edema, swelling and necrosis
130
What are types of bacteria isolated from cases of anaerobic cellulitis in small animals? These are also bacteria commonly isolated from bite wounds.
- Bacteroides
- Peptostreptococcus
- Fusobacterium
- Porphyromonas
- Clostridium
- Prevotella
131
What is the likely susceptibility of anaerobic bacteria causing anaerobic cellulitis?
- Metronidazole
- Chloramphenicol
- Amoxicillin clavulanate
- Aside from Bacteroides, susceptibility to ampicillin or clindamycin can be expected
- Susceptibility of facultative anaerobes can be unpredictable and limited
132
What are general treatment recommendations for anaerobic cellulitis?
- Surgical debridement
- Hyperbaric oxygen treatment
- Oral antibiotics
133
a) What is the most common bacteria culture from dog and cat bite wounds? b) What are other bacterial cultured from dog and cat bite abscessed?
a) Pasteurella multocida
b) Staphylococcus pseudintermedius
- beta hemolytic staphylococcus
- Bacteroides
- Peptostreptococcus
- Fusobacterium
- Porphyromonas
- Clostridium
- Prevotella
134
What is the likely susceptibilty pattern of Pasteurella multocida?
- Penicillins (penicillin, amoxicillin, amoxicillin clavulanate)
135
a) What is a bacterial pseudomycetoma?
b) What other names does it go by?
c) What causes this to form?
d) What is the pathogenesis of this entity?
e) How does this clinically present?
f) What IHC stain is best used to visualize the organisms?
g) What are common treatment recommendations?
a) Chronic, suppurative, granulomatous disease caused by non-branching bacteria that form grains of compact colonies in tissues that are surrounded by pyogranulomatous inflammation; causative bacteria is typically coagulase-positive Staphylococci; some cases other bacteria ( Pseudomonas, Proteus, Streptococcus, Actinobacillus) alone or in combination with Staphylococci can occur
b) cutaneous bacterial granuloma, botryomycosis
c) Most cases initiated by local trauma from bites or wounds, can also occur secondary to foreign bodies
d) There is a delicate balance between the virulence of the organisms and response to the host; the host is able to isolate snd contain the infection but unable to eradicate it.
e) Firm, solitary or multiple nodules with draining fistulae; purulent exudate may have small white granules similar to grains of sand.
f) Gram Stain or Brown-Brenn stain?
g) Complete surgical excision for isolated lesions; With large numbers of lesions, cotreatment with rifampin and beta-lactamase resistant antibiotic may be effective.
136
List XX pathogens that can cause tissue grains?
- Coagulase positive Staphylococci (i.e. bacterial pseudomycetoma/botryomycosis)
- Actinomyces
- Nocardia
- Mycetomas
- Actinobacillosis
137
What diseases demonstrate Hoeppli-Splendore material?
- Botrymycosis
- Actinomycosis
- Actinobacillosis
138
What is Hoeppli-Splendore material?
- Brightly-eosinophilic, radiating and clubbed deposits seen on H&E
- Represents an antigen-antibody reaction around infectious agents or parasites that occurs at the periphery of organized aggregates of organisms
139
a) What organisms can cause tuberculosis in dogs and cats?
| b) What clinical signs can they present with?
a) Mycobacterium tuberculosis; Mycobacterium bovis; Mycobacterium microti (There is a higher incidence of M. bovis in cats)
b) Respiratory and digestive lesions; can develop localized skin lesions - single or multiple ulcers, abscesses, plaques and nodules; nodules may be in skin or adhered to subQ tissue; they may discharge a thick, yellow to green malodorous pus; lesions found on head, neck and limbs
140
What organisms causes tuberculosis in voles, wood mice and shrews? How can cats become exposed to this pathogen?
Mycobacterium microti; cats become exposed through altercations while hunting; this species can also cause infect humans and larger mammals, particularly domesticated llamas in Europe.
141
What can be used to test dogs for TB?
- bacille Calmette-Guerin (BCG) or purified protein test (PPD) prepared for humans can be used to test dogs; best to perform on inner surface of pinnae.
- Cytological examination including Ziehl-Neelsen (ZN_ staining for acid-fast bacilli
- Biopsy and culture
- Lymphocyte blastogenesis test in cats
142
What species of mycobacterium are included in the Mycobacterium avium comples ?
- M. avium subspecies avium
- M. avium subspecies hominissus
- M. avium subspecies paratuberculosis
143
What breeds are predisposed to disseminated MAC due to immunodeficiency?
- Abysssinian and Somali cats
| - Cats with retroviral infections or a history of immunosuppressive therapy
144
What is a bizarre feature of disseminated MAC in Abyssinian cats?
Failure of hair to regrow after clipping
145
What are the treatment recommendations for MAC infection in cats?
- Rx. three antimicrobials for 2 months, then continue 2 antimicrobials for an additional 6 months
- Combination of rifampin, a fluoroquinolone and clarithromycin or azithromycin
- Continuation period of rifampin with either a fluoroquinolone or clarithromycin/azithromycin
146
What fluoroquinolones are most effective in treating MAC infections ?
Marbofloxain, moxifloxacin, pradofloxacin?
147
Aside from rifampin, clarithromycin and fluoroquinolones, what other oral antibiotics can be useful?
Doxycycline, clofazimine
148
What is feline leprosy syndrome?
- A granulomatous, nodular, cutaneous infection of cats with acid-fast bacilli that are difficult or impossible to culture.
- Thought to be caused by trauma from infected rodents during hunting of outdoor cats
- Caused by:
1) Mycobacterium lepraemurium (syndrome in young cats caused by infection with the rat leprosy bacillus)
2) Mycobacterium visible ( syndrome of older cats)
3) A previously unnamed novel Mycobacterial species, now called "Mycobacterium lepraefelis"
4) Mycobacterium tarwinense
149
What is the cause or murine leprosy?
Mycobacterium lepraemurium
150
What are the clinical features of feline leprosy syndrome?
Varies depending on the infective species:
1) Mycobacterium lepraemurium - infection in adult males less than 5 years of age; initial lesion is a focal granuloma, additional lesions may develop, growth can be rapid with spread to surrounding areas. Lesions remain localized but can become widespread; ulceration or larger masses with formation of abscesses or fistulae with no signs of healing; head, limbs and small lesions can occur on the planum nasale, lips and tongue. Typically painless and no signs of systemic disease
2) Mycobacterium lepraefelis (previously unnamed species) : disease of older cats (>9 years); generalized nodular skin disease which may develop from localized lesions or be generalized from the start; Dx developes slowly over months to years, nodules do not ulcerate
3) "Feline multisystemic granulomatous mycobacteriosis" associated with diffuse cutaneous disease and widespread dissemination to internal organs - causes by M. visible
4) Mycobacterium tarwinense - both young and old cats affected with lepromatous lesions (i.e. lots and lots of AFB bacteria) on the head and limbs; follows indolent and progressive course
151
How is feline leprosy syndrome diagnoses?
- History, physical exam findings, detection of acid-fast bacilli in smears from needle aspirates, crush preparations of biopsy specimens or histo (ZN or fite-faraco stains required)
- Organisms causing Feline leprosy syndrome are fastidious, culture is usually negative, PCR amplification is required for species I.D.
152
What is the difference between tuberculoid response (i.e. paucibacillary) and lepromatous leprosy?
- Tuberculoid response (i.e. paucibacillary): caseous necrosis and relatively few organisms, AFB only found in areas of necrosis
- Lepromatous leprosy (i.e. multibacillary): granuloma comosed of solid sheets of large foamy macrophages containing large numbers of AFB; generally indicated a poor host immune response
153
What type of inflammation does mycobacteria stimulate?
pyogranulomatous to granulomatous
154
What treatment options are typically recommended for feline leprosy syndrome?
- Wide surgical excision when possible
- Combination of two to three antimicrobials considered most effective
- Clofazimine has best reported success for M. lepraemurium
- Clarithromycin, rifampin and clofazimine used in other species of mycobacterium
- continue treatment for at least 2 months after lesion resolution
155
What is canine leproid granuloma syndrome?
- localized nodular skin disease of otherwise healthy dogs that is usually confined to the head and especially EARS; mycobacteria have been readily demonstrated by cytological examination and in biopsy samples but causative organism has not been identified (known to be a slow-growing mycobacterial species)
- Asymptomatic nodules confined to skin and subcutis of head and ears, Large lesions can ulcerate
- Thought that insects serve as mechanical vectors
- Spontaneous resolution of lesions is typical within 1-3 months of onset
156
What breeds appear to be pre-disposed to canine leproid granuloma?
- Short-coated dogs, particularly boxers and their crosses
157
What treatment options are considered for canine leproid granuloma syndrome?
- Lesions spontaneously resolve within 1-3 months of onset typically
- For severe or refractory cases, a combination rifampin and clarithromycin could be considered; doxycycline could be used instead of clarithromycin
158
What species are involved in rapidly-growing (also referred to as opportunistic/atypical/nontuberculous) mycobacteriosis?
- Mycobacterium fortuitum group (M. fortuitum, M. perigrinum and third biovariant complex)
- Mycobacterium chelonae/abscessus group (M. chelonae, M. abscessus)
- Mycobacterium smegmatis (M. smegmatis, M. goodiee, M. wolinskyi)
- Mycobacterium phlei
- Mycobacterium thermoresistible
159
What three syndromes are recognized to be associated with atypical mycobacteriosis?
- Mycobacterial panniculitis involving chronic infection of the subcutis and skin
- Pyogranulomatous lobar pneumonia
- Disseminated systemic disease (only seen in severely immunocompromised animals)
160
What is the pathogenesis behind atypical mycobacteriosis?
- These organisms are ubiquitous in the environment and free-living in nature; are typically harmless. They occur in soil, dirt, water tanks, swimming pools, tap water and sources of natural water.
- Disease typically follows a penetrating injury/wound contaminated with soil/dirt, particularly bite or cat fight wounds but also include contaminated injections.
- Bites to the neck, dorsal trunk, flanks, raking injuries causes by claws of the hind limbs, injections or surgery
- the causative agents thrive in fatty tissues; infection occurs especially in obese animals
161
What are the clinical features of atypical mycobacteriosis?
- Initially lesions may resemble cat bite abscesses
- Plaques and nodules develop at the site of injury
- Lesions develop as non-painful, non-pruritic, firm or fluctating subcutaneous nodules or swellings that ulcerate and spread outwards, new satellite lesions developing at the edges
- Thickening of the subcutis with adherence of the associated skin occurs; affected area becomes alopecic with skin thinning and development of punctate fistulae that discharge a watery exudate
- Nonhealing wounds present for several months
- Lesions can occur anywhere, but most commonly occur in the cat in the caudal abdomen/inguinum or in the lumbar region.
- Lesions can also occur
- Lesions may or may not be painful; lymph nodes may or may not be enlarged
- Hypercalcemia can occur with significant granulomatous infeciton
162
What media should be used to culture atypical mycobacteria?
- 5% sheep blood agar and Lowenstein-Jensen medium
| - 1% Ogawa egg yolk medium
163
How is atypical mycobacteriosis diagnosed?
- Finding AFB in smears, cultures of deep biopsy speciments
| - Organism is DIFFICULT to demonstrate microscopically
164
What are the histlogic features of atypical mycobacteriosis?
- nodular to diffuse dermatitis, panniculitis or both due to pyogranulomatous inflammation.
- Stains including Fite-Faraco and Ziehl-Neesen can be used to highlight organisms?
- Organisms are often clumped in the center of a clear vacuole and surrounded by clusters of neutrophils within mature granulomas
165
What are empiric medications for atypical mycobacteriosis?
As these organisms can be cultured, ideally choose drugs based on susceptibility results; hower you can can start
- Doxycycline, a fluoroquinolone and/or clarithromycin as soon as a diagnosis is made
- A combination of moxifloxacin and clarithromycin will cover almost all organisms likely to be encountered in companion animals
- Surgical resection with removal of infected tissue is necessary
166
What is Mycobacterium smegmatis typically resistant to?
Usually susceptable to a wide range of antimicrobials but oftentimes resistant to CLARITHROMYCIN
167
What is the typical susceptibility profile of M. chelonae?
May be resistant to all common antimicrobials aside from CLARITHROMYCIN, MOXIFLOXACIN and LINEZOLID.
168
Actinomycosis
- Gram-positive, non-acid fast, catalase positive, filamentous anaerobic rods that are opportunistic commensals of the oral cavity and bowel
- Infection occurs from trauma and contamination of penetrating wounds, especially those involving foreign bodies including awns and quills
- Hunting/field dogs in warm climated most commonly affected
169
What are the clinical features of actinomycosis?
- subcutaneous swelling or abscess of the head, neck, thoracic, paralumbar or abdominal region
- Lesions are tender and may or may not have draining tracts
- Paralumbar lesions are often a direct extension from retroperitoneal involvement
- Draining tracts may discharge a thick yellow-gray or thin hemorrhagic foul-smelling exudate that may contain yellow sulfur granules
170
How is actinomycosis diagnosed?
- Anaerobic culture
- Direct smears of fine-needle aspirats and biopsy using stains (Gram, Brown-Brenn, GMS)
- Cytologic study appears to be most effective
171
What are the histologic features of actinomycosis?
Nodular to diffuse dermatitis, panniculitis or both due to suppurative or pyogranulomatous inflammation
- Tissue grains (i.e. sulfur granules) seen in 50% of cases
- Granules are basophilic
- Gram-positive, filamentous to beaded organisms are found within the granules
172
What are the treatment recommendations for actinomycosis?
- Surgical excision or debulking
- Long course of antibiotics; typically high-dose penicillins (i.e. penicillin, amoxicillin, oxacillin) are optimal
- Other drugs that may or may not be effective: clindamycin, erythromycin, cephalosporins, chloramphenicol, tetracycline
- Continue treatment for at least 1 month after complete remission; typically last for 3-4 months
- Prognosis is guarded, relapses frequenrly occur.
173
What is the causative agent of actinobacillosis? what is the general pathophysiology behind this diseasE?
Actinobacillus ligniersii; a gram-negative aerobic coccobacillus.
- This is a normal commensal organism found in the mouth of many animals, clinical lesions follow bite wounds or injuries around the face and mouth.
174
What are the clinical features of actinobacillosis?
Resembles actinomycosis
- single or numerous thick-walled abscesses of the head, neck, mouth and limbs that discharge a thick white-green odorless pus with soft yellow granules
- A cause of basophilic tissue grains and surrounded by eosinophilic Hoeppli-Splendore material.
175
What are the treatment recommendations for actinobacillosis?
- Surgical extirpation
- Drainage/curettage
- Sodium iodide
- High dosages of streptomycin or sulfonamides
- Organism is usually sensitive to tetracycline and chloramphenicol
176
What is the cause of Nocardiosis?
```
Rare pyogranulomatous and suppurative infection of the skin or lungs or by widespread dissemination and caused by Nocardia spp, which are common soil saprophytes. Cause infection by wound contamination, inhalation, and ingestion (especially in immunocompromised animals)
-Organisms involved include the
Nocardia asteroides complex (type I-VI)
- Type III : Nocardia nova
- Type V: Nocardia farcinia
Nocardia braziliensis
Nocardia otitidiscaviarum
```
177
What kind of bacteria are Nocardia?
Gram-positive, partially acid-fast, branching, filamentous aerobies.
178
What is the main species of Nocardia affecting cats?
Nocardia nova
179
What are the clinical features of nocardiosis?
Cellulitis, ulcerated nodules, abscesses with draining sinuses. Lesions occur in areas of wounding especially on the limbs and feet. Cats oftentimes have lesions on the ventral abdomen and resemble panniculitis or opprortunistic mycobacterial infections.
180
How can Nocardia spp. be distinguished from Actinomyces spp?
Nocardia are partially acid-fast with a modified Fite-Faraco stain and usually branch at right angles; when the organisms are branched and beaded, the orgabisms appear similar to Chinese characters.
181
What are general treatment recommendations for Nocardiosis?
- Surgical drainage and antibacterial therapy
| - Prognosis is guarded
182
What are effective empiric antibiotics for Nocardiosis?
- Potentiate sulfonamides
- Erythryomycin
- Clarithromycin
- Cephalosporins
- Chloramphenicol
- Tetracyclines
- Various parenteral drugs
183
What is the pathomechanism behind streptococcal toxic shock syndrome?
Causes by group C streptococci, especially S. Canis
- unclear why this bacteria becomes so toxic to dogs
- Most strains are positive M protein and streptolysin O, which are probably virulence factors
- Rapidly progressive, intensely painful wound with deep necrosis; wound is disproportionately painful
- Dogs experience rapid development of sepsis and shock or sepsis with necrotizing fasciitis.
184
What are treatment recommendations for streptococcal toxic shock syndrome?
- antibiotics with either a macrolide or beta-lactam antibiotic
- Area of fasciitis requires debridement
- With aggressive treatment, the disorder may not be fatal
- Hyperbaric oxygen therapy may be beneficial
185
What are the clinical features of staphylococcal toxic shock syndrome?
- Generalized macular erythema of the trunk and limbs, often with marked edema, particularly of the limbs
- Vesicles and ulcers
- Variable crusting
- Pyrexia, anorexia, severe malaise
186
What are cutaneous manifestations of brucellosis?
Causes by Brucella Canis
- May produce a secondary scrotal dermatitis resulting from the animal's licking the skin over the painful epididymitis and orchitis
- Some cases result in necrosis of the testis with severe inflammation of the entire scrotum and draining ulcers
- Reported from a 15 month old female lab beagle with lesions that resembled acral lick dermatitis
187
What is plague?
- Acute febrile infectious disease
- Caused by Yersinia pests, a bipolar coccobacillus of the family Enterobacteriaceae; a facultative anaerobic, nonmotile, non spore-forming organism that cannot penetrate unbroken skin but can invade mucous membranes
- Three forms: bubonic, pneumonic and septicemia
188
What animals are most suseceptible to plague?
Rodents (especially prairie dogs) and cats; dogs are less susceptible ; dogs are resistant to infection
189
What is the most common form of plaque and how does it present?
Bubonic; localized abscesses form near the site of infection (especially along the head and neck)
- Septicaemic and pneumonic forms are more serious because they may not be diagnosed until its too late
190
How is plague transmitted?
Fleas or ingesting infected animals
191
What is the most common rodent-flea that transmits plague?
Diamanus montanus
| - There are also four less common rodent-hosted fleas
192
What are the drugs of choice for treating plague in small animals?
- Gentamicin with or without rifampin
- Chloramphenicol
- Tetracycline
- Fluoroquinolones
- Local abscesses should be opened, drained carefully and irrigated daily with an antibacterial solution
- Flea control is important to prevent further spread
193
What is erythema chronicum migrans?
Characteristic expanding ring-like macule or papule developing 1-2 weeks at the site of a tick bite
194
What oral antibiotics would be effective against abscesses involving mycoplasma (a normal oral flora)
Treatment for extended periods of time with macrolide, lincosamides, the tetracycline group, or the fluoroquinolones should be effective
195
what is the asexual stage of a fungus called?
An anamorph
196
What is the sexual stage of a fungus called?
A teleomorph
197
What are the ingredients in dermatophyte test medium?
- Chloramphenicol
- Gentamicin
- Cycloheximide
198
What are molds that produce pigment called?
Dematiaceous fungi
199
What are molds that do not produce pigment called?
Hyaline fungi
200
What are special stains used in histopathology to highlight fungal organisms?
- Mayer's mucicarmine stains - stains cryptococcal polysaccharide capsule red
- Gomori's methenamine stain - stains fungal organisms black
- periodic-Acid Schiff - stains fungal organism
201
Dermatophytosis
infection of the keratinized tissue (claw, hair, stratum corneum) caused by a species of Microsporum, Trichophyton or Epidermophyton
202
What are fungal cell walls composed of
- Chitin
- Chitosan
- Glucan
- Mannan
* LACK CHLOROPHYLL*
203
What is a mycelium?
A mass of of hyphae
204
What does coenocytic mean?
Sparsely septate fungal hyphae with numerous nucleai within a cell
205
What is a conidium (pl: conidia)?
An asexual propagule that gives rise to genetically identical organisms
206
What is a conidiophore?
a simple or branched mycelium bearing conidia or conidiogenous cells
207
What are the six major types of conidia?
1) Blastoconidia
2) Arthroconidia
3) Annelloconidia
4) Phialoconidia
5) Poroconidia
6) Aleuriconidia
208
How are oomycetes different from fungi?
- Oomycete cell walls are composed primarily of beta-1,3-glucan polymers and cellulose with very little chitin
- Oomycetes utilize mycolaminarin (a beta-1,3 glucan) for energy storage; diploidy at the vegetative state
- Oomycetes have a complex life cycle involving both sexual and asexual reproduction; oomycete asexual reproduction involves formation of a sporangium that produces motile zoospores bearing two flagella
- Oomycete zoospores adhere to the surface of plants or animals, germinate and then penetrate into tissues of the host
- Fungal cell walls contain large amounts of chitin and ergosterol; fungi are haploidy at the vegetative state
209
Mycotic diseases are typically divided into what three categories?
- Superficial
- Subcutaneous
- Systemic
210
What are the most common normal fungal flora of dog skin?
- Alternaria
- Aspergillus
- Aureobasidium
- Chrysosporium
- Cladosporium
- Mucor
- Penicillium
- Rhizopus
- Dermatophytes
211
What are the most common normal fungal flora of cat skin?
- Alternaria
- Aspergillus
- Chrysosporium
- Cladosporium
- Mucor
- Penicllium
- Rhodotorula
- Scopulariopsis
- Dermatophytes
- Cats with FeLV/FIV have greater diversity
212
What is the cause of athlete's foot in humans?
-Trichophyton rubrum
213
What are the three main tissue reactions to fungal infections?
1) Acute suppurative inflammation with microabscess formation
2) Chronic inflammation - may be pyogranulomatous or granulomatous
3) Necrosis, which occurs when fungi invade blood vessels resulting in infarction and tissue death
214
Are nystatin and amphotericin B effective against dermatophytes?
NO
215
What do azole antifungals do?
Inhibit the production of:
- ergosterol
- triglyceride
- Phospholipid
- Chitin
- Oxidative and perioxidative enzymes
216
What are the three most common causes of dermatophytes in small animal practice?
- Microsporum canis
- Microsporum gypseum
- Trichophyton metagrophytes
217
What is the seasonality of dermatophytes in dogs and cats?
a) Microsporum canis: high from October to February and low from March to September in dogs; little seasonal variation in cats
b) Microsporum gypseum: high from July to November, low from December to June in dogs; rarely reported in cats; slight increase in summer and fall months
c) T. mentagrophytes: present all year in dogs, peak in November and December; rarely reported in cats but may occur in summer/fall months
218
What is the vector/natural host for Microsporum persicolor?
Mice and voles
219
What is the infective portion of a dermatophyte?
The arthrospore, formed by segmentation and fragmentation of fungal hyphae
220
List X natural host defenses against dermatophytosis?
- Dryness
- Desquamation
- Fungistatic properties of sebaceous and apocrine gland secretions
221
What keratinase produced by M. canis may be associated with more inflammation and pruritus?
u (i.e. mu) - chymotrypsin-type serine proteinase
222
What fungal components may elicit immunologic reactions?
- Cell wall carbohydrates (chitin and mannan)
- Cell wall proteins (glycoprotein)
- Secreted keratinases
223
What can predispose an animal to dermatophytosis?
- It is believed that cell-mediated immunity is the mainstay of of the body against fungal infection
- FeLV
- FIV
- cancer
- Poor nutrition
- anti-inflammatory or immunosuppressive drug therapy
- Stress of pregnancy and lactation
- Presence of ectoparasites (including fleas and cheyletiella)
- Genetic influences
224
What pathogen(s) are associated with dermatophytic kerion lesions?
- M. gypsum or T. metagrophytes; usually are solitary lesions that occur on the face or limb
225
What pathogen(s) are associated with onychomycosis?
- T. metagrophytes in the dog; M. canis in the cat
226
What is the typical distribution of dermatophytosis?
- Typically lesions are localized, with lesions most commonly occurring on the face, pinnae, paws and tail.
227
What is "sylvatic ringworm"?
Dermatophytes acquired from wild mammals
228
What is the only breed of cat that dermatophytic pueudomycetoms have been reported in?
Persians
229
What is the only breed of cat that dermatophytic pueudomycetoms have been reported in?
Persians
230
What percentage of human contract dermatophytosis after exposed to a symptomatic or asymptomatic infected cat?
50%
231
How long are athrospores in the environment infectious for?
12-24 months
232
What species of dermatophytes are wood-lamp positive?
- Microsporum canis
- Microsporum audouinii
- Microsporum distortum
- Trichophyton schoenleinii
233
Which species of dermatophytes do not invade hair and are only found in scales?
- Microsporum persicolor
| - Epidermophyton floccosum
234
What are the three most common histologic patterns seen in dermatophytosis?
1) Perifolliculitis, folliculitis and furunculosis
2) Hyperplastic or spongiotic superficial perivascular or interstitial dermatitis with prominent parakeratotic or orthokeratotic hyperkeratosis of the epidermis and hair follicles
3) Intraepidermal pustular dermatitis
235
How long can can M. canis spores persist in the environment for ?
18 months
236
What is the average duration of treatment for onychomycosis?
Always requires an oral antifungal, typically requires 6-12 months of therapy
237
List 4 reasons for chronic and recurring cases of dermatophytosis
1) Inappropriate therapy (wrong drug, dose, duration of therapy, not using topicals, failure to clip the haircoat, failure to treat all other animals in the house, failure to treat the environment)
2) Underlying diseases: hypercortisolism, diabeted mellitus, FeLV infection, FIV infection, cancer
3) Immunosuppressive drug therapy
4) Genetic background of the patient
238
What are common recommendations for elimination of dermatophytosis in a cattery or other multiple-cat facilitity?
- Separation of carriers from non-carriers
- Treatment or removal or infected animals
- Aggressive systemic and topical therapy
- Interruption of breeding programs and show campaigns
- Isolation of the colony
- Environmental decontamination
- Testing and isolation of future cattery or house-hold members
239
What is the minimum amount of time typically invested in treating dermatopytes?
12-16 weeks
240
Malassezia pachydermatis
- A lipophilic, non-lipid dependant, nonmycelial saprophytic yeast
- Also known as Malassezia canis, Pityrosporum pachydermatis and Pityrosporum canis
- Virulence factors include proteases, lipases, phospholipases, lipoxygenases, phosphatases, phosphohydrolase, glucosidase, galactosidase, leucine, arylamidase, urease, zymoasan
- These virulence factors contribute to pathogenesis, inflammation, proteolysis, lipolysis, alteration of local pH, eicosaonoid release and complement activation
- Malassezia dermatitis histologically characterized by prominent exocytosis of CD3+ lymphocytes and subepithelial accumulation of mast cells which suggest hypersensitivity
- Pre-disposing risk factors: increased humidity, immunologic dysfunction (especially cell-mediated immunity and IgA), chronic glucocorticoid administrations, FIV infection, thymoma, pancreatic adenocarcinoma, genetics (strong breed predilections), hypersensitivity diseases, keratinization defects, recurrent bacterial skin infections and endocrine diseases
- Number of malassezia is significantly greater in the groin, interdigital spaces, ear canals, under the tail base of atopic dogs relative to normal dogs
- Malassezia colonization can be enhanced/symbiotic when present with S. pseudintermedius
- In cats, can cause black, waxy otitis; recalcitrant feline chin acne; facial dermatitis with tightly adhered scales and follicular casts; refractory paronychia; generalized scaly to waxy dermatitis;
- Devon rex may be predisposed to paronychia with M. pachydermatis
- Scaly, erythematous, greasy to waxy pruritic dermatitis
241
List 6 lipid-dependant species of Malassezia
1) Malassezia furfur (i.e. Pityrosporum ovale)
2) Malassezia globosa
3) Malassezia obtusa
4) Malassezia restricta
5) Malassezia slooffiae
6) Malassezia sympodialis
242
What adhesion molecules / ligands are involved in malassezia attachment to corneocytes?
- Trypsin-sensitive proteins or glycoproteins on yeast cell walls are important for adherence to canine corneocytes
- Mannosyl-bearing carbohydrate residues on canine corneocytes serve as ligands for adhesins expressed.
243
What breeds are predisposed to malassezia dermatitis?
- West Highland White Terrier
- Basset Hound
- American Cocker Spaniel
- Shih Tzu
- English setter
- Toy and miniature poodles
- Boxer
- Cavalier King Charles Spaniel
- Australian and silky terriers
- German shepherd dog
- Dachshund
244
What are some cytologic criteria investigators have used to suggest malassezia dermatitis.
* * There is not a definitive number of malassezia organisms required to diagnosed Malassezia dermatitis
1) Greater than 10 organisms in 15 randomly chosen oil-immersion microscopic fields using tape strip samples
2) Average of four or more organisms visible per oil-immersion microscopic field
3) When an average of four or more organisms are visible per oil-immersion microscopic field
4) When an average of one or more organisms is visible in 10 oil-immersion microscopic fields
5) When greater than two organisms per high power field are found
* ** The diagnosis of malassezia dermatitis is based on response to antiyeast treatment
245
What medium can be used to culture Malassezia?
- Malassezia pachydermatitis: non lipid-dependant, can be grown on Sabouraud dextrose agar
- Other malassezia species are lipid-dependant
- Modified Dixon agar and Leeming medium grow all Malassezia species and are preferred for isolating malassezia from cats
246
Chromomycosis
Subcutaneous and systemic diseases caused by fungi that develop in host tissue in the form of dark-walled (pigmented, dematiaceous) fungal elements. Can be further separated into two forms:
1) Phaeohyphomycosis: organisms appear as septate hyphae and yeast-like cells
2) Chromoblastomycosis: fungus is present as large (4-15 um diameter) rounded, dark-walled cells (sclerotic bodies, chromo bodies, Medlar bodies)
247
Hyalohyphomycosis (aka adiaspiromycosis)
Encompasses all opportunistic infections caused by nondematiaceous fungi
- basic tissue forms of these being hyaline hyphal elements that are septate, branched or unbranched and nonpigmented in tissues
- Examples: Fusarium, Pencillium, Scedosporium, Geotrichum, Paecilomyces spp. (also referred to as Paceilomycosis), Monocilliym indicum
248
Zygomycota
Includes the orders Mucorales and Entomophthorales
- Zygomycosis is used to include both mucormycosis and entomophthoromycosis
- These organisms are angiotropic, their invasion into blood vessels results in embolization and necrosis of the surrounding tissues
249
Mycetoma
- Unique infection wherein the organism is present in tissues within granules or grains associated with tumefaction and draining sinuses
- Can be Eumycotic or actinomycotic
- Caused by dematiceous fungi (i.e. black grained mycetomas) or non-pigmented fungi (white-grained mycetoma)
- Pseudomycetoma (i.e. a dermatophytic pseudomycetoma; bacterial pseudomycetoma/botryomycosis) has different granule formation.
250
Sporotrichosis
- Causes by ubiquitous, dimorphic, saprophytic fungus: "Sporothrix schenkii"
- Infection secondary from inoculation of the organism into the subcutaneous tissue
- In environment, exists as a mycelial form growing on living and decaying plant matter; also found on barberry and rose bush thorns, tree bark, sphagnum moss, straw and moldy hay
- Disease in dogs typically secondary to puncture wounds cause by thorns or splinters or wounds contaminated by soil or other organic material
- Infections in cats commonly occur in free-roaming males and may be acquired through contaminated claws or teeth during fights
- After inoculation, sporothrix converts to its yeast form
- May proliferate at inoculation site causing localized or fixed disease, it may spread up regional lymphatics producing lymphangitis and lymphadenitis, or may disseminate hematogenously to other visceral organs
- This has zoonotic potential and can be spread to humans who otherwise have no pre-existing wounds/bites/scratches; infected cats more likely to transmit infection.
- Cytology: suppurative-pyogranulomatous-granulomatous inflammation; pleomorphic yeast that is round, oval, or cigar shaped.
- Histopathology: nodular to diffuse, suppurative to granulomatous dermatitis; lots of fungal organisms seen in cats, not so many in dogs.
- Fungi have a refractile cell wall but NO CAPSULE
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Canine sporotrichosis
- Uncommon, hunting dogs may be increase risk due to punctures of wounds via thorns or splinters
- Cutaneous form: multiple firm nodules, ulcerated plaques with raised borders, annular cursted and alopecic areas; commonly on head, pinnae and trunk; some lesions have verrucous appearance; nodules may ulcerate/develope draining tracts
- Lesions non-painful nor pruritic, animals otherwise healthy
- Cutaneouslymphatic form: nodule on distal aspect of one limb, ascending infection via lymphatics with secondary nodules forming along lymphatic vessels which may be firm or fluctuant (called cording of lymphatics). Nodules ulcerate and discharge red/brown exudate
- Disseminated sporotrichosis is extremely rare in dogs
- Treatment: supersaturated solution of potassium iodide; monitor for signs of iodide toxicity; azole antifungals could also be considered
252
Feline Sporotrichosis
- Uncommon in cats; infection believed to be secondary to inoculation of the organism by contaminated claws or teeth from another cat
- Typically seen in intact free-roaming male cats
- Lesions common on head, distal limbs, tail base
- May initially present with fight wound abscesses
- May be spread to other areas on the body from normal grooming behavior.
- Some cats are lethargic, depresses, anorexic and pyrexic
- Cats frequently have lymph node and lymphatic vessel involvement
- Most cats are FeLV/FIV negative
- Produce much larger numbers of fungal organisms on cytology and histopathology
- Always think about sporo in cats with non-healing fight-wound abscesses
- Treatment: Itraconazole +/- terbinafine; monitor serum liver enzymes once monthly when animal is on itra.
- Prognosis for cure is guarded.
253
What are the three cardinal features of a eumycotic mycetoma?
1) Tumefaction
2) Draining tracts
3) Grains in the discharge
254
What are mycetomas?
Pyogranulomatous nodules that contain tissue grains or granules composed of dense colonies of organisms an necrotic debris
255
What are the causes of eumycotic mycetomas?
- Fungi that are ubiquitous soil saprohphytes that cause disease via wound contamination, a contaminated splinter or injury
- Disease rare in USA and EU
- Causative species include:
1) Black-grain/dark-grain mycetomas, usually Curvularia geniculata and occasionally with:
- Cladophialophora bantiana
- Exophiala jeanselmei
- Macrophomina spp.
- Leptosphaeria spp
- Madurella mycetomatis
- Madurella grisea
- Pyrenochaeta
- Staphylotrichum spp.
- Torula spp.
2) White-grain mycetomas (i.e. unpigmented fungi) are usually causes by Pseudallescheria (i.e. Allescheria, Petriellidium, Scedosporium) boydii and occasionally Acremonium hyalinum.
- Treatment recommendation: Wide surgical excision, azoles are occassionally effective, terbinafine may help.
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What is the most common cause of Eumycotic mycetoma in the USA?
The unpigmented fungi, Pseudallescheria boydii; the asexual form is called Scedosporium apiospermum. Causes white-grain mycetomas.
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What is phaeohyphomycosis?
- Causes by a number of ubiquitous saprophytic fungi found in various soils and organic materials
- Infection occurs via wound contamination, especially through wood splinters and bited
- Immunosuppression may increase likelihood to disseminated disease
- Fungi have characteristic pigmented (diatomaceous) hyphen elements BUT NOT GRAINS in tissue
- Pigment may be light yellow-dark brown; pigment is melanin (stains with Masson-Fontana)
- Scedosporium prolificans is a common cause of phaeohyphomycosis in humans.
- Rare in dogs, uncommon in cats
- Cause single or multifocal poorly circumscribed nodules that may ulcerate or develop draining tracts; in cats most common on face, distal extremities or trunk.
- In cats, lesions may resemble chronic bacterial abscesses or thick walled cysts.
- Cytology: granulomatous-pyogranulomatous inflammation, pigmented fungi may be visible
- Histo: nodule to diffuse granulomatous to pyogranulomatous dermatitis and panniculitis, numerous fungal elements present with irregularly pigmented septate branched or unbranched hyphae; occasional chlamydoconidia.
- FUNGI BEST DEMONSTRATED WITH MASSON-FONTANA STAIN.
- Treatment: wide surgical excision followed by antifungals; as there is a wide number of species that can cause this, susceptibility testing is recommended.
- Causes in dogs: Alternaria spp., Bipolaris spicferum, Cladophialophora bantiana, Curvularia spp, Exophiala spp, Phialemonium obovatum, Phialophora spp, Pseudomicrodochium suttonii, Scedosporium spp, Wangiella spp.
- Causes in cats: Alternaria spp, B. spiciderum, C. bantiana, Exophiala jeanselmei, Exophiala spinifera, Fonsecaea pedrosoi, Microsphaeropsis arundinis, Moniliella suaveolens, Macrophomina spp, Phialophora verrucosa, Cladophialophora spp, Dissitimurus exudrus, Scolecobasidium humicola and Stemphylium spp.
- German shepherds may be predisposed
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What is hyalohyphomycosis (i.e. adiaspiromycosis)?
- Opportunistic infections by NON-PIGMENTED fungi that form hyphal elements in tissues
- Numerous fungi implicated as causes; the genera most commonly identified in skin lesions of dogs and cats are Acremonium, Fusarium, Geotrichum, Paecilomyces, Pencillium and Pseudallescheria.
- Fungi are generally saprophytic molds found in soil and water; usually inoculated into tissues through wounds or by invasion of mucosal surfaces; may disseminate to other sites in immunosuppressed individuals
- German shepherds may be predisposed
- Commonly found on claw beds, skin, eyes (cornea) joints
- Organisms can be normal flora / lab contaminants, documentation of invasion disease requires submission of biopsies
- Cytology: suppurative to pyogranulomatous inflammation with broad, septate, non pigmented hyphae, same can be seen on histopath
- Treatment: Few dogs survive disseminated hyalophyphomycosis, surgical removal followed by antifungal azaleas and/or amphotericin B is recommended. Various species have widely different susceptibilities, recommend fungal culture and sensitivity to guide therapy.
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What is zygomycosis?
- Zygomycetes are class of fungi that are ubiquitous saprophytes of soil/decarying vegetation; known to be component of normal skin and hair coat
- Isolated from insects and feces of amphibians and reptiles
- May enter via GI, respiratory or cutaneous via wound contamination; insect bites may also be a port of entry.
- THREE ORDERS IN THIS CLASS INCLUDING:
1) Mucorales: include genera Rhizopus, Mucor, Saksenaea, Absidia
2) Mortierellales: include the genus Mortierella
3) Entomophthorales: include the genus Conidiobolus and Basidiobolus
- Rare infection in dogs and cats, most infected animals have FATAL GI DISEASE.
- Solitary to multiple, nodular, ulcerated and draining skin lesions, usually on the extremities.
- Cytology: pyogranulomatous to granulomatous inflammation WITH NUMEROUS EOSINOPHILS
- Histo: nodular to diffuse pyogranulomatous to granulomatous dermatitis panniculitis containing numerous EOSINOPHILS; inflammation centered on amorphous eosinophil material that occasionally contains clear spaces representing poorly stained hyphae.
- Vascular invasion and hematogenous spread is more common with Mucorales (i.e. mucomycosis)
- Hyphae often surrounded by eosinophilic sleeves (Splendore-Hoeppli phenomenon)
- Fungal elements most commonly found and most abundant in regions of necrosis
- Can grow on Sabouraud dextrose agar; Potato flake agar with ampicillin and streptomycin is excellent culture medium for this species.
- Do not grind / macerate tissues as may destroy organisms.
- Treatment: surgical excision / debunking of solitary lesions followed by systemic antifungals as dictated by susceptibility testing.
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What is pythiosis?
- Pythium insidiosum is the species isolated from dogs, cats, humans and horses; from the class "Ooomycete"
- Aquatic organism that rely on aquatic plants and other organic substances for their normal life cycle
- Differ form fungi in that they produce motile flagellate zoospores and have cell walls that contain cellulose and beta-glucan with NO chitin and LITTLE ergosterol
- Motile zoospore attracted to damaged plant or animal tissue and hairs; loosed flagella and becomes encysted on tissue; then develops germ tubes in the direction of tissue and penetrate with invasion of hyphae elements
- Animals infected after standing in or drinking stagnant water; damaged skin required for prerequisite for infection
- Environmental conditions most important influential factors; most cases occur summer/fall in tropical and subtropical areas.
- Seen in Gulf coast region in USA, also New Jerser, Virginia, Kentucky, Indiana, Illinois, Arizona etc. GI form of pythiosis has been reported in California.
- Dog: cutaneous or GI disease, rarely both; Labrador retrievers and German shepherds seem to be predisposed; large breed, young male dogs and those involved in hunting or outdoor activities may be pre-disposed.
- Typical history of exposure to warm bodied of water
- solitary or multiple lesions typically confined to one area, especially the legs, face or tailed; ulcerated nodules develop rapidly into boggy masses with ulceration/draining tracts; typically pruritic
- Discharge is mixture of pus and blood; may contain "kunkers" which are accumulation of yellowish-gritty coral-like bodies; composed of pythium spp. hyphae surrounded by necrotic tissue and inflammatory cells
- GI pythiosis: weight loss, vomiting, diarrhea, hematochezia; segmented transmural thickening of GI tract; mesenteric lymph nodes embedded in palpable granulomatous mass
- -> CAT: rare; nodules with ulcerations and draining tracts on the limbs and ventral abdomen; some have large subQ masses on distal limbs with no involvement of overlying integument.
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How is pythiosis diagnosed and treated?
- Cytology: granulomatous to pyogranulomatous inflammation where eosinophils are numerous, occasional fungal elements seen.
- Histo: nodular to diffuse granulomatous to pyogranulomatous dermatitis and panniculitis with numerous eosinophils; inflammation centered on foci of necrosis and amorphous eosinophilic material; hyphae somtes invade blood vessels resulting in thrombosis
- Hyphae surrounded by eosniphilic sleeves of splendor hoeppli phenomenon
- Hyphae difficult to see on H&E, can see with GMS, BUT NOT PAS.
- Grows rapidly on blood agar and Sabouraud dextrose agar; using vegetable extract agar containing streptomycin and ampicillin or Campy blood agar will increase likelihood of finding P. insidiosum.
- Do not freeze tissue for culture as this will kill organisms.
- ELISA useful for diagnosis and monitoring response to therapy; there should be dramatic decrease in antibody levels within 2-3 months after successful treatment.
- Treatment: Wide surgical excision (sometimes requires amputation) followed by post-operative itraconazole/terbinafine for 2-3 months after surgery; you should follow ELISA serology to follow response to therapy.
- Caspofungin (potent inhibitor of beta-glucan) may be more effective but extremely expensive.
- Pythium vaccine contains exoantigens and cytoplasmic antigens, stimulates both Th2 and Th1 response, may make lesions look more inflamed; dogs with chronic disease (>2 months) unlikely to respond
262
What is lagenidiosis?
- Lagenidium is another oomycete that can infect animals
- Typically parasitize age, fungi, shrubs, rotifers, nematodes, crustaceans and insect larvae; little known about life cycle about species that infects dogs
- Majority of cases involve young-middle aged dogs in the southeastern USA that swam in lakes and ponds
- Multifocal firm, derma or subQ nodules that ulcerate and develop draining tracts
- Has NOT been reported in cats
- Regional lymphadenopathy often present; vasculitis and infection of great vessels, sublumbar and inguinal lymph nodes, lung, pulmonary hills and cranial mediastinum can occur.
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How is lagenidium diagnosed and treated?
- Cytology or LN aspirate: pyogranulomatous to eosinophilic inflammation; may reveal broad poorly septate hyphae
- Hyphae are LARGER than those of pythium
- Skin biopsies should be submitted for history AND PCR
- Need PCR to differentiate from Pythium
- Histo: pyogranulomatous-eosinophilic inflammation with presence of broad, thick walled, irregularly shaped hyphae.
- Usually seen on HE and highlighted with GMS stains
- Preferred culture medium: peptone-yeast-glucose agar with ampicillin and streptomycin
- Treatment: aggressive surgical resection, amputation recommended if distal extremity is affected.
- Systemic disease common, recommend imaging of thorax/abdomen prior to surger
- Recommend concurrent itraconazole/terbinafine as an adjuvant to surgical resection
- Prognosis for systemic disease is grave.
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Blastomycosos (i.e. Gilchrist or Chicago disease)
- Caused by Blastomyces dermatitidis is caused by a dimorphic, saprophytic fungus
- The gene "bys-1" controls change from mycelial to yeast phase
- Infection acquired by inhalation of spores from mycelial growth in the environment
- Spores settle in terminal airways and transform into yeasts that establish a primary infection of the lungs
- Organisms may disseminate through body via blood and lymphatics
- Uncommonly, focal lesions develop from inoculation of spores into a puncture wound
- Dogs are 10 X increased risk of infection compared to humans
- Very rare in cats; Siamese cats may be predisposed
- Clinical signs: anorexia, weight loss, coughing, dyspnea, ocular disease, lameness, skin disease
- In endemic areas, fungus is not widely distributed; most people living in endemic regions show no serologic or skin test evidence of exposure.
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What environmental conditions support growth of blastomycosis?
What regions in the USA are considered endemic hot spots for blastomycosis?
A) Moist, acidic soil rich in organic matter; decaying wood and animal waste substrates; beaver dams provide an ideal location for Blasto; rain, heavy dew and soil disturbances favor the release of infectious spores.
B) Mississippi, Missouri, New York, Ohio and St. Lawrence River Valleys and the Mid-Atlantic states.
266
What are the elements highlighted in the "micro focus model" to predict where Blastomycosis will occur?
1) Moisture
2) Soil type (sandy, acid)
3) Presence of wildlife
4) Soil disruption
267
List two important virulence factors that are important for adherence of Blastomyces yeast to host cells and act as immune modulators?
BAD1
| WI-1
268
What organ systems can be involved in Blastomycosis?
- Lungs: 85% of of dogs
- Eyes: 40% of cases - uveitis, chorioretinities, optic neuritis, retinal detachment, retinal granulomas, vitrifies, keratitis.
- Bone: 30% of cases
- Skin: 20-25% of dogs
- Lymph nodes
- Subcutaneous tissues
- External nares
- Brain
- Testes
269
What signalment and lifestyle predispose to canine blastomycosis?
- Young (2-4 years old) intact male dogs of large and sporting breeds (Dobermans, Labradors, Blue tick coonhounds, treeing Walker coonhound, pointers, Weimeraners)
- Large number of cases occur in the fall
- Proximity to a body of water was a significant risk factor for affected dogs
270
What skin lesions are seen in blastomycosis and where do they occur?
Multiple papules, nodules, plaques, ulcers, draining tracts, subcutaneous abscesses.
Can occur anywhere, oftentimes involving the nasal plant, face and claw beds.
271
How is blastomycosis diagnosed?
- History of traveling to or living in an endemic area should increase suspicion
- Cytology: suppurative - granulomatous - pyogranulomatous inflammation with round to oval, yeastlike fungi
- YEAST SHOW BROAD-BASES BUDDING and have THICK REFRACTILE DOUBLE-CONTOURED CELL WALLS.
- Histo: nodular to diffuse, suppurative to pyogranulomatous to granulomatous dermatitis where the fungus is typically found.
- In-hospital fungal cultures not not recommended due to risk of infection from the mycelial form of the organisms.
- Fungus highlighted with GMS, PAS or Gridley fungal stain
- Serologic testing can help establish a diagnosis
- Detection of Blastomyces dermatitis antigen from urine, serum, CSF, and BALF fluid; urine most sensitive for disseminated disease, BALF most sensitive for pulmonary blastomycosis. False positives can occur due to cross-reactive with histoplasma capsulatum, Aspergillus and Cryptococcus neoformans. Measuring antigen levels may help with evaluating response to therapy; antigen levels decline with treatment.
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How is Blastomycosis treated?
- Spontaneous remission is rare
- Itraconazole is the drug of choice for dogs; more effective than ketoconazole, as effective as AMB, and can be given at home and equal cost to AMB; treat for a minimum of 60 days for at least 1 month after all clinical signs of disease resolve.
- Also can consider Amphotericin B lipid complex combined with an azalea antifungal
- Fluconazole may be as effective as Itra
- Death may occur after first 7 days of treatment in up to 50% of dogs with severe lung disease due to inflammatory response to dying fungi, consider short course of dexamethasone or prednisolone in conjunction for the first few days to hedge inflammatory response.
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Coccidioidomycosis
- Dimorphic, saprophytic soil fungus
- most human and canine inhabitants of endemic areas become infected with many infections being subclinical or causing only mild/transient respiratory disease.
- Major route of exposure is by inhalation; arthroconidia enter bronchioles and alveoli and extend into the peribronchiolar tissue
- In lungs, arthroconidia transform into large, round, thick-walled spherical cells called spherules, which are filled with endospores.
- Organism may disseminate by hematogenous routes to: bones, skin, eyes, heart, pericardium, testicles, brain, spinal cord, spleen, liver and kidneys.
- Skin lesions: papules, nodules, abscesses, draining tracts, ulcers.
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What environmental conditions support Coccidioides?
- Sandry, alkaline soils, high environmental temperatures, low rainfall and low elevation
- This area is called the "Lower Sonoran Life Zone"
- Includes southwestern United States, Mexico, Central and South America.
- Rainfall and activities that disturb soil release arthroconidia which are then dispersed by wind.
- Coccidioides immitis found in San Joaquin Valley of California
- Coccidioides pgsadasii found in other areas including Arizona, Texas, New Mexico, Nevada, Utah, Canada
275
How is coccidioidomycosis treated?
- Spontaneous remission is unlikely
- Animals with bone or CNS involvement have a guarded prognosis
- Azole antifungals: ketoconazole, itraconazole, fluconazole
- Disseminated disease should be treated for a minimum of 1 year and 3-6 months after remission of clinical signs
- Ampho B may be used to treat animals that cannot tolerate or do not respond to azole antifungals.
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What are the clinical finding of a) dogs and b) cats with coccidioidomycosis?
a) Uncommon; young male dogs predisposed; Boxers and Dobermans predisposed to disseminated disease
- coughing, dyspnea, waxing/waning pyrexia, anorexia, weight loss, lameness, skin disease, ocular disease; skin lesions reported to almost always occur over sites of infected bone.
b) Rare in cats; anorexia, weight loss, fever, cough, dyspnea, lameness, ocular disease and skin lesions.
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How is coccidioidomycosis diagnosed?
- History of travel to an endemic area should increase suspicion
- Cytology: suppurative-granulomatous-pyogranulomatous inflammation; fungal elements may appear in the form of spherules or endospores but may be difficult to find
- Histo: nodular to diffuse, suppurative-granulomatous-pyogranulomatous dermatitis and panniculitis; fungal elements easier to find if sections strained with PAS OR GMS
- Do not culture in vet practices due to risk posed to humans.
- Serology useful for diagnosis
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What are the most common species of Cryptococcosis (also called European blastomycosis and torulosis)?
- Cryptococcosis is the most common systemic mycosis in cats; there are 37 species within the genus Cryptococcus. The two most common infective species include:
- C. neoformans is a ubiquitous yeastlike fungus most frequently associated with the droppings and filth and debris of pigeon roosts
- Eucalyptus and other trees implicated as environmental niche for C. gatti in tropical/subtropical climates; koal bears may serve as sentinels
1) Cryptococcus neoformans: primarily infects immunosuppressed individuals
2) Cryptococcous gatti: capable of infecting immunocompetent hosts
- C. neoformans divided into three subtypes: C. neoformans var. neoformans (serotype D), C. neoformans var. gatti (serotypes B and C) and C. neoformans var grubii (sertoype A).
- Nitrogen-rich, alkaline environment of pigeon guano promotes the growth of cryptococcal organisms which may remain infected for over 2 years
- Primary route of infection is inhalation; occasional cats get localized lesions from inoculation
- Most cases begin with colonization of nasal mucosa with hematogenous spread to lymph nodes, skin and bone; infection may extend through cribriform plate causing meningoencephalitis
- Establishment and spread of infection are highly dependent on host immunity; underlying disease often not detected in dogs/cats with crypto
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List some of cryptococcus' virulence factors
- Polysaccharide capsule: composed of glucuronoxylomannan; two capsular genes - CAP59 and CAP64 - have been associated with virulence; capsule thickens following invasion of a host and protects the organism by blocking inflammatory reactions and interfering with phagocytosis
- Melanin: protects fungal cells from toxic hydroxyl radicals and oxidative stress
- Mannitol
- Lactase
- Phenol oxidase
- Enzymes
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What signalment and clinical signs of dog/cat is associated with developing crypto?
- Dog: young, large breed dogs may be predisposed; increased incidence in Doberman pinschers, German Shepherd dogs, Great Danes, American cocker spaniels
- Rhinosinusitis and various abnormalities of CNS and eyes; infection may disseminate to internal organs; skin lesions seen in 20% of cases and are a marker of disseminated disease
- Cats: young adult cats; siamese may be predisposed; upper respiratory, cutaneous, central nervous and ocular systems; 70% of cats have a flesh-colored, polyp-like mass visible in the nostril or a firm - mushy subcutaneous swelling over the bridge of the nose; cats with nasopharyngeal cryptococcosis develop inspiratory stertor and use open mouth breathing; mandibular lymphadenopathy is common; blindness can occur.
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What are the skin lesions seen in dogs and cats with cryptococcosis?
- Skin lesions seen in 20% of dogs with crypto and 40% of cats with crypto
- Dogs: papules, nodules, ulcers, abscesses and draining tracts affecting the nose, lips, clawbeds
- Cats: typically multiple papules, nodules, abscesses, ulcers and draining tracts anywhere, but commonly involving the face, pinnae, paws
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How is cryptococcosis diagnosed?
- Cytology: granulomatous - pyogranulomatous inflammation with numerous pleomorphic yeastlike organisms
- Yeasts show narrow-budding and are surrounded by a mucinous capsule of variable thickness which forms a clear or refracticle halo
- INDIA INK STAIN RECOMMENDED AS ORGANISM DOES NOT TAKE UP STAIN AND APPEARS AS SILHOUETTES
- Diff-Quik, Gram stain and new methylene blue stains can be used to make cytologic diagnosis
- Histo: cystic degeneration or vacuolation of the dermis/subcutis that is acelular, sometime likened to infusion of soap bubbles; or nodular to diffuse pyogranulomatous - granulomatous dermatitis and panniculitis containing numerous organisms.
- Mayer muciramine is useful because stains the capsule red.
- Stain can also be visualized using PAS, GMA, or Fontana-Masson stains.
- Cryptococcal capsular antigens can be detected in serum and CSF using latex agglutination test; false positives reported with cross-reactions with disinfectants/soap; recommended to use to monitor response to therapy
- Serum titers persist with/without clinical signs for months/years after initial diagnosis and treatment
- Grows well on Sabouraud dextrose agar; Birdseed agar containing antibiotics recommended when culturing a site, such as nasal cavity, where there may be heavy bacterial contam.
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How is crypto treated?
- Surgical excision of large masses of fungal infected tissue
- Amphotericin B and flucytosine for cats with CNS disease
- Azole antifungals recommended for less severely affected animals
- Fluconazole: good efficacy against crypto and penetrates well into CSF and ocular tissues although resistance reported
- Itraconazole: favourable therapeutic index, considered drug of choice for treatment of most cases of crypto
- Therapy should be continued long-term to ensure infection is eliminated; sometimes requiring over 2 years in some patients
- Continue treatment until patient is healthy and no organisms found on cytology or culture; serial monitoring serum antigen titers useful because patients improve clinically long before infection totally eradicated
- If titer not decreased after a few months, more aggressive therapy should be considered; treatment continue until antigen titer is 0
- Recheck titer 6 months after stopping therapy
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Histoplasmosis
- Caused by histoplasma capsulatum; a dimorphic saprophytic soil fungus
- Prefers warm, moist, humid conditions and soil containing nitrogen-rich organic matter such as bird and bat excrement; decaying wood is another source.
- TWO VARIETIES: Histoplasma capsulatum var. vapsulatum & Histoplasma capsulatum var. duboisii.
- Teleomorph: Ajellomyces capsulatus
- Most cases occur in the Ohio, Missouri, Mississippi River valleys.
- Most humans and dogs in edemic areas become infected but most infections are subclinical.
- Usually microconidia are inhaled; once in lungs, microconidia convert to the yeast phase. Yeast are engulfed by phagolysosomes within macrophagses and may be disseminated via lymphatic and blood vessels to organs that a right in mononuclear phagocytes.
- May also infect via ingest; GI histoplasmosis without respiratory tract involvement suggests ingestion may be another route.
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What are the clinical findings of dogs and cats with histoplasmosis?
- Dog: uncommon disease in endemic regions; young dogs usually affected; pointers, weimeraners and Brittany spaniels are predisposed; anorexia, weight loss, fever, coughing, dyspnea, GI disease, ocular disease and skin disease. Most common clinical manifestation is large-bowel diarrhea w/ tenesmus; hepatosplenomegaly, visceral lymphadenopathy, icterus, ascites
- Cat: uncommon disease in endemic areas; most cats less than 4 years old, most have disseminated disease; clinical signs include depression, weight loss, fever, anorexia, dyspnea, ocular disease and skin disease.
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How is histoplasmosis diagnosed?
- Travel to endemic region should increase suspicion
- Cytology: pyogranulomatous to granulomatous inflammation containing numerous small round yeast bodies with basophilic center and lighter halo.
- Histop: nodular to diffuse pyogranulomatous to granulomatous dermatitis with numerous intracellular organisms
- Thoracic radiographs: linear to diffuse interstitial pattern with hilar lymphadenopathy
- AUS: hepatosplenomegaly, visceral lymphadenopathy
- Rectal scraping good source of tissue to evaluate for organisms
- Antigen deteciton assay identifies polysaccharide antigen of H. capsulatum in serum, CSF, BALF or urine ; recommendded for monitoring therapy; antigen levels decrease with effective therapy
- Serology positive in most patients; can take 2-6 weeks between infection and development of antibody response.
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How is histoplasmosis treated?
- All should be treated due to potential for generalized dissemination
- Drug of choice: Itraconazole
- Severe/fulminating cases: Itraconazole and AMB
- Fluconazole and Ketoconazole are NOT recommended
- Voriconazole shows promise for treating CNS infections
- Good prognosis; long-term treatment often required
- CNS, eyes, bones and testicles most difficult to treat
- Airway obstruction from hilar lymphadenopathy can occur, steroids may help with itra in these patient
- Continue treatment until antigenemia and antigenuria have cleared
- Monitor antigens every 3-6 months for 2 years after treatment discontinued to ensure relapse caught early.
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Candida
- Candida are dimorphic fungi from family Cryptococcaceae
- Yeast phase of Candida are normal inhabitants of alimentary, upper respiratory and genital mucosa
- Candida albicans and Candia parapsilosis isolated from ears, nose, oral cavity and anus of normal dogs and dogs with candidiasis
- Cause opportunistic infections of skin, mucocutaneous areas, external ear canals and claws
- Factors that disrupt normal microflora or disrupt normal cutaneous/mucosal barriers provide a pathway for Candida
- Can be secondary to an underlying immunosuppressive or debilitating systemic disease including hyperadrenocorticism, diabetes mellitus, hypothyroidism, cancern, immunodeficiencies, immunosuppressive drug therapy
- Once in the body, further spread correlates to cell-mediated immunocompetence and neutrophil function
- Candida produce proteinases and keratinases and phospholipases that degrade stratum corneum and facilitate penetration.
- Rare disease in dogs; foul-smelling nonhealing ulcers with thick whitish gray plaques w/ erythematous borders along oral mucocutaneous junctions; papules-pustules-oozing plaques - ulcers; white vaginal or preputial discharge
- Extremely rare in cats: erythem/erosions/ulcers/crusts/oozing
- Cytology: suppurative inflammation and numerous yeasts and budding cells (i.e. blastoconidia); pseudohyphae occur on occassion; narrow-based and multilateral budding.
- Grows on Sabouraud dextrose agar' the API 20c system is convenient and reliable for ID
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What is Piedra?
- Fungal infection of the extrafollicular portion of the hair shaft by either Piedrai hortae (black piedra) and Trichosporon beigelii (white piedra); white piedra has been described in a dog.
- Also called trichomycosis nodularis
- Seen nodules along hair shafts consisting of extrapilar and intrapilar hyphae arranged perpendiculalry to the hair suface; septate hyphae and arthroconidia may be visible
- Trichosporon beigelli growns on Sabouraud dextrose agar but is inibited by cyclohexidimide
- Shave off all hair or treat with antifungal topical therapy
- Spontaenous remission is common.
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Rhinosporidiosis
- Caused by Rhinosporidium seeberi
- May be a member of the newly recognized group of human and animal pathogens called Mesomycetozoea
- Endemic in India and Argentina; reports from Southern United states
- Associated with aquatic environment
- Infective unit is a small round spore that developes in tissue to large, spherical bodies called sporangia
- Infection through mucosal contact with stagnant water/dust/trauma
- Infection involves mucous membranes of the nasal cavity, ear, pharynx, larynx, trachea, esophagus, urogenital mucosae, skin
- Elicits severe pyogranulomatous reaction
- Large breeds male dogs more often affected
- Wheezing, sneezing, unilateral seropurulent nasal discharge and epistaxis
- Results in red, pink or grayish sessile or pedunculated nasal polyps and covered with pinpoint white foci (sporangia), may protrude out or involve the mucocutaneous area
- Cytology or histo diagnostic
- Histo: fibrovascular polyp wth numerous sporangia with a thick, double outer membrane
- Surgery is treatment of choice
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Rhodotorula dermatitis
- very fungal infection by saprophytic Rhodotorula spp.
- Yeastlike fungi are opportunistic pathogens of immunosuppressed patients
- Diagnosed in 1 FeLV/FIV positive cat with crusts on nasal planum, nostrils, bridge of the nose, periocular region and one digit
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Aspergillus dermatitis
- Aspergillus spp. are ubiquitous fungi; exist in nature as soil and vegetation saprophytes and component of normal skin, hair coat and mucosae
- Produces opportunistic infections by invading musocal or cutaneous surfaces
- Aspergillus fumigatus most common species encountered in nasal aspergillosis
- Cutaneous and mucocutaneous infections have only been reported in dogs; few cases of sinonasal asper have been reported in cats
- Dolicocephelic and mesocephalic breeds are at increased risk
- Can cause inflammation, depigmentation, ulceration and crusting of the externa nares and , occassionally, the nasal planum secondary to nasal discharge.
- Most disseminated aspergillosis occurs in German shepherds.
- In disseminated cases: cutaneous nodules, abscesses, draining tracts, oral ulcers.
- Cyto: suppurative to pyogranulomatous inflammation with fungal elements occassionally visualized.
- Biopsy: nodular to diffuse suppurative or pyogranuloatous dermatitis or necrotizing dermatitis with minimal inflammation; orgaisms usefully plentiful
- Asper can be grown on Sabouraud dextrose aga.
- Rhinoscopy allows visualization of fungal plaques (white, yellow, or light green molds)
- Treatment: thiabendazole or ketoconazole variably effective; Amphotericin B and itraconazole most effective.
- Continue treatment 3-4 weeks beyond clinical cure with a minimum of 6-8 weeks of treatment.
- Nasal asper: enilconazole administered topically twice daily through tubes implanted in each nasal chamber.
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Alternaria dermatitis
- Alternaria spp. are ubiquitous saprophytic fungi in soil and organic debris and common component of flora of canine/feline integument
- Cause opportunistic wound infections
- Can cause alopecia, erythema, scaling; nodular, ulcerated depigmented inflammation of the nose (Alternaria tenuissima)
- In the cat, associated with phaeohyphomycosis and ulcerated nodules on the paw.
- cyto and histo reveal pyogranulomatous inflammatin and numerous fungal elements.
- Grows on Sabouraud dextrose agar
- Recommend surgical excision of nodules and antifungal chemotherapy based on susceptibility tests.
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Trichosporum dermatitis
- Trichosporon spp. are soil saprophytes in family Cryptococcaceae that form minor component of normal cutaneous and musocal flora
- Can cause cutaneous and systemic disease.
- Previously thought the main agent was Trichosporon cutaneum, but six species are important in causing infections
- Trichosporon beigleii causes white piedra in humans, monkeys and horses
- T. beigelii and T. pullulans have caused infections in cats with mixed suppurative to granulomatous inflammation of mucosal/submucosal and subcutaneous tissues.
- One cat: unilateral mass protruding from nostril and inspiratory stidor; another cat- chronic ulcerative subcutaneous lesions at site of a bite wound; two other cats have had chronic hematuria, dysuria and chronic cystitits from this year.
- Need to biopsy for Dx.
- Histo: abscesses and nodular infarcts with fungal organisms invading blood vessels resulting in thrombosis.
- Spherical - oval yeast organisms can be seen in tissue sections.
- Can be cultured on Sabouraud agar.
- Treat cats with Itraconazole; surgical removal or debulking should be performed is nasal granulomas present.
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Protothecosis
- Prototheca are ubiquitous, saprophytic, achlorophyllous algae found in soil, raw and treated sewage, slime flux of trees, animal wastes, tap water, freshwater streams, swimming pools and contaminated stagnant water
- Cause opporunistic infections; disseminated disease associated with dysfunction of host immunity
- For disseminated infections, colon thought to be main portal of entry
- Wound contmination thought to be portal of entry for cutaneous lesions
- Prototheca wickerhamii: isolated from cutaneous infections in dogs and cats
- Prototheca zopfii: nearly always isolated from disseminated infections in dogs
- Lesions with large numbers of organisms typically have little surrounding inflammation until therapy is started
DOG: rare; collies are predisposed; in systemic form, intermittent bloody diarrhea most common, can spread to kidneys, liver, heart, brain and eyes; dogs with disseminated disease frequently have colitis but rarely have skin lesions
- Dogs with cutaneous/mucocutaneous disease rarely have systemic disease; papules/nodules/ulcers over pressure points and mucocutaneous junctions (nostrils), scrotum and footpads; depigmentation of the **nasal planum may be striking**; lesions may become generalized (joints, lymph nodes, heart, lungs)
- CAT: rare; only cutaneous involvement has been reported; all cats healthy otherwise; solitary or multiple skin lesions; firm papular/nodular masses on paws, legs, nose, head, pinnae, base of tail; only P. wickerhammi has been isolated.
- Biopsy: nodular-diffuse pyogranulomatous to granulomatous dermatitis and panniculitis with numerous fungal elements
- Grows on sabouraud dextrose agar
- Presence of organisms in urine sediment is an indication of disseminated disease
- Treatment: solitary lesions can be surgically removed; Amphotericin B and itraconazole are the current recommended therapies; aminoglycosides or tetracyclines may be alternative drugs
- Therapy is usually prolonged (2-4 months) and should be continued for 3-4 weeks beyond clinical cure.
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What species is associated with pustular dermatophytosis?
- Typically associated with keratin-colonizing dermatophytes
- Typically a facially predominant disease but can become generalized in immunosuppressed individuals
- Typically associated with Trichophyton mentagrophytes particularly T. mentagrophytes var. erinacei (hedge hog is the natural species for this)
