Mycology Flashcards
Fungus
Widely distributed organism No chlorophyll Nucleus Spore productins Asexual/sexual With filamentous and branching structures evolved with cell walls containing chitin (or cellulose) Unicellular or multicellular eukaryotes Non-photosynthetic Saprophytes, mutualistic symbionts, parasites Aerobes- 25-37deg Tolerate high osmotic pressures and acidic environments Heterotrophic
Heterotrophic
Produce exoenzymes and obtain nutrients by absorption
Fungal structure
Rigid cell wall
-mannan, chitin, cellulose, glucan, chitosan
-chitin (polysaccharide) provides rigidity and structural support
-ergosterol=dominant sterol
Nucleus, mitochondria, ribosomes
Microtubules
Molds: multicellular filaments
Yeasts: unicellular spheres
Dimorphic fungi: either or depending on temp
Yeasts
Oval, spherical or elongated single cells
3-5um
Reproduce by budding or both budding and spore formation
Molds
Filamentous with branching filaments or hyphae (long filaments of cells joined together)
2-10 um in diameter
Mycelium: filamentous mass of hyphae (large fluffy colonies on lab media)
Vegetative mycelium
Develops inside the substrate, provides support and absorbs nutrients
Aerial hyphae
Vertically growing hyphae- might have fruiting bodies
Reproductive mycelium
differentiation of aerial hyphae to support the fruiting bodies
Septate hyphae
septa divide hyphae into compartments, not into cells
Non-septate
Coenocytic hyphae
Dimorphic fungi
Change from mycelial form at room temp to year at 37 (body tissues)
Change is regulated by factors like temp, co2 concentration, pH
Asexual
Very effective
produced by mitosis
Two main types: sporangiospores, conidia
Fission of somatic cell
Division of nuclei by mitosis
Budding
Cell wall bulge out and daughter nucleus migrates into bud
Fragmentation of hyphae
each disjointed hyphae becomes a new organism
Sporulation
Followed by germination of spores
Sporangiospores
formed within sporangium (sac-like structure) borne on an aerial hyphae termed sporangiophore
Conidia
Formed on conidiospores
Sexual
Only demonstrated in few fungi
Fusion of two haploid nuclei followed by meiotic division of diploid nucleus
Arthroconidia
(A) Spores formed and released during hyphal fragmentation
Blastoconidia
(A) Conidia are produced by budding from a mother cell, hyphae or pseudohyphae
Chlamydoconidia
(A) Thick-walled resistance spored formed by some fungi in unfavorable environmental conditions
Macroconidia
(A) Large multi-celled conidia which are produced by dermatophytes in culture
Microconidia
(A) Small conidia produced by certain dermatophytes
Phialoconidia
(A) Conidia produced from phialides
Sporangiospores
(A) Spores are released when mature sporangium ruptures
Zygospores
(S) develop in a thick walled zygosporangium, formed from fusion of side projections of two compatible hyphae (+/-)
Basidiospores
(S) produced on club-shaped structures called basidia
Ascospores
(S) Develop in a sac-like structure (ascus)
Predisposing factors to fungal tissue invasion
Opportunistic! Immunosuppression Prolonged antibiotic therapy Immunological defects Immaturity, ageing Malnutrition Exposure to heavy challenge of fungal spores Traumatized tissue Persistent moisture on skin surface Some neoplastic conditions
Mechanisms involved in fungal diseases
Mycosis: Tissue invasion
Mycotoxicosis: toxin production
Induction of hypersensitivity
Dermatophytosis: general characteristics
Infection caused by dermatophyte or “fingworm fungi” in the keratinized tissues (including hair, feathers, stratum corneum layers of skin, nails, claws, horns
Ringworm
Zoonotic
Arthrospores are infectious forms
Geophilic dermatophytes
Inhabit and replicate in soil associated with decomposing keratinous material
Zoophilic dermatophytes
Obligate pathogens of animals (host specific)
Anthropophilic dermatophytes
obligate pathogens of humans
Microsporum
M. canis, M. gypseum, M. nanum, M. gallinae
Invade hair and skin
M. canis most common
Thick-walled multiseptated macroconidia (fusiform to obovate)
Microconidia are sessile or stalked, clavate, arranged singly along hyphae
Trichophyton
T. mentagrophytes, T equinum, T. verrucosum
Invade hair, skin, nails, horns, claws
Althetes foot in humans
Thin-walled and smooth macroconidia, rarely produced and in small numbers
Macroconidia are cylindrical, clavate to cigar shaped
Dermatophytosis:CS
Infecting strain and host immune status
Alopecia, erythema, scaling, crusting, annular-ringed lesions, vesicles or papules
Trichophyton infections more severe than microsporum bc inflammation
Dermatophytosis: transmission
Arthrospores-> shedded by infected animal and viable for months to years in environment
Direct contact with infected animal
Exposure to arthrospores in environment or fomites
Dermatophytosis: pathogenesis
Spores from soil/animal/human
Dermatophytes (invade skin abrasions -keratin layers)
enter stratum corneum
Release keratinase, protease, elastase
Inflammatory reaction (redness, swelling, heat, alopecia)
Movement away from site of infection to next hair follicle
Central healing with classical ringed lesion
Canine ringworm
M. canis, M. gypseum, T. erinaceid, T. mentagrophytes
Lesions: brittle hair, dry and scaly skin, crusts and scabs
Infection with T. mentagrophytes -> kerion: intense inflammation, swelling, ulceration, purulent exudate
M. gypseum (compulsive burying of objects in soil)
T. mentagrophytes (good rate catchers)
T. erinaceid (avid hedgehod worriers)
Feline ringworm
M. canis (cats serve as primary reservoir)
Often asymptomatic -> public health risk!
Lesions: circular areas of stubbed hair, alopecia, mild scaling and folliculitis at the head
Most common in kitten with immature immune system and adults with immune deficiency
Feline otits: persistent waxy ceruminous otic discharge when caused by M canis
Bovine Ringworm
Trichophyton verrucosum
Calves are more susceptible. Incidence higher in winter
Lesions: circular, scattered, accompanied by skin scaling and alopecia; large plaques may develop with the formation of thick scabs and crusts
Severe inflammation, pruritis (secondary bacterial infection?) Spontaneous resolution after this stage
Porcine Ringworm
Microsporum nanum (M. canis, M. gypseum, T. mentagrophytes)
Common disease, affecting large breeds
Higher incidence with high density and humidity, and poor sanitation
Lesions: circular, roughened, mildly inflamed; anywhere on body
Equine Ringworm
Trichophyton equinum, M gypseum
Lesions: multible, dry, scaly raised lesions on any body part; inflammation and exudates cause hair to mat together and enlarged lesions create a moth eaten appearance
Infections often become chronic and subclinical, but recur under stress
Avian Ringworm
Favus= White Comb
M. gallinae
Lesions: white patches on comb of infected male birds
Occasionally disease may extend to feathers
Dermatophytosis Diagnosis
Wood’s lamb examination of lesions (50-60% test positive)
- M canis infected hairs may fluorescence green when illuminated with long-wave UV-light
- use these hairs for sampling
Direct microscopic examoination
- examine hairs from lesions and scales
- fine, hyaline, septate hyphae in keratine scales and in hair shafts
- arthroconidia on hair
Microscopic morphology: typical macroconidia structure
Physiological tests: temp tolerance, urease production, invitro hair perforation test
Culturing
Sampling: cleanse area with alcohol (reduce bact contamination) -> hair clipped from long haired animals -> collect sample from periphery of lesion -> scrape skin and pluck hair
Dermatophyte test medium
Microsporum canis culture: spreading whitish, cottony surface growth with a golden-yellow reverse pigment
Microscopic morphology: typical macroconidia structure
Dermatophyte test medium
Sabourauds dextrose agar with peptones, antibiotics, cyclohexamine and phenol red pH indicator
Incubate 35-30 C unless T verrucosum which is 37C
Growth with red slant before 10 days= dermatophyte (increase in pH because it used peptones first as E source and so became alkaline)
Growth with yellow slant turnes red AFTER 10 days= non dermatophyte (brown/black hyphae; eats sugars first so is acidic- then eats peptones)
Dermatophytosis: treatment
Removal and/or killing of fungus on skin and hair
- clipping if long haired
- shampoos, dips, sprays
- topical antifungal
Systemic therapy
- griseofulvin
- Azoles
- terbinafine
Treat until 3 neg cultures
Dermatomycoses- general characteristics
Yeasts and normally saprophytic filamentous fungi causing cutaneous infections resembling dermatophytosis
Dermatomycoses- predisposing factors
High humidity and excessive wax accumulation Hairy and pendulous ears Neoplasm Allergies Change in quality or quantity of sebum Presence of other dermatoses Recent antibiotic or glucocorticoid therapy Trauma
Dermatomycoses- Malassezia spp
Lipophilic yeast, opportunistic pathogens
M. furfur, M. pachydermatis, M. sympodialis, M. globosa, M. obtuse, M restricta, M dermatis, M nana, M slooffiae
Members of the normal cutaneous for a: skin, lips, vagina, anal sacs, external ear canal of dogs
Predisposing factores
Peanut shaped
Otitis Externa
M. Pachydermatis
CS: head shaking, pruritis, offensive odor, chronic otitis
Dx: otoscopic examination of ear canal
Cytological examination for bacteria, yeasts and mites
Tx: identify and eliminate predisposing factors, tropical antifungals, and systemic antimicrobials (middle ear infection)
Seborrheic Dermatitis
M. Pachydermatis
Superficial dermatitis as regionalized disease affecting ventral abdomen, face, feet, neck, perineum, leg folds or generalizd disorder
CS: face rubbing, foot licking, erythematous and scaly skin, alopecia, hyperpigmentation and lichenification
Breed predisposition: poodles, cocker spaniels, chihuahuas, GSD, boxers, basser hounds
Predisposing facotrs: allergies, seborrhea
Dx: history of poor response to antibiotics, glucocorticoids, and immunotherapy and demonstration of yeast cells on skin scrapings or swabs
Tx: removal of predisposing factors, shampoos, creams, or dips with selenium sulfide, miconazole, ketoconazole, chlorohexidine
Tx for systemic disease: oral ketoconazole
Trichosporon spp
Nasal mass is cats
- occludes naris
- surgical excision
- follow up with parenteral administration of ketoconazole
Geotrichum candidum
Ubiquitous saprophyte in soil and decaying organic matter
Isolated from faeces of healthy clinically normal animals
Occasionally implicated in diarrhea in dogs and apes
Geotrichosis in reptiles and amphibians: cutaneous lesions, nodular, well-circumscribes dermo-epidermal masses
Subcutaneous mycoses-general characteristics
Broad range of infections involving deeper layers of skin, muscle, bone, connective tissue
Typically associated with injuries (traumatized tissue)
Etiological agents:
-in soil or decaying vegetation
-dematiaceous (brown pigmented) or hyaline (colorless) molds and dimorphic fungi
Infections are chronic and insidious
Organisms establish in skin -> localized infection of surrounding tissues and lymph nodes
Dx: careful microscopic/pathological examination
Sporotrichosis
Sporothric schenckii
Dimorphic, dematiaceous fungi
-yeast =37C: cigar shaped, pleimorphic budding yeast cells
-mold =25C: thin septate hyphae with tapering conidiophores bearing conidia in rosette-like cluster
World-wide- more tropical
Isolated from soil, vegetation, peat moss, and wood
Conidia are inoculated into skin by puncture wounds from thorns or bites
Sporotrichosis- lesions
Dogs, cats, horses etc
Lesions begin at point of entry and consist of subcutaneous nodules that ulcerate and heal
lesions not painful
Disease may follow course of lymphatic vessels and involve lymph nodes
Sporotrichosis- CS
In dogs
Cutaneous: localized, multicentric
Lymphocutaneous: nodules along lymphatics
Disseminated: rare, potentially fatal
In humans
Rose handler’s disease
Sporotrichosis Pathogenesis
Molds and conidiophores from soil, decaying and senescent vegetation
Conidia or mycelia
Enter through broken skin
Changes from mycelia form to yeast or parasitic form
Virulence factors: thermotolerance, acid phosphatases, proteinases I and II, adhesion
Lymphocutaneous manifestation: nodules at site of entry
Infection spreads along lymphatics
Sporotrichosis- diagnosis
Lesions of cats tend to have larger number of yeasts
Direct microscopy
Culture: moldy colonies in 2-7 d on SDA at 25. Cream colored, wrinkled, leathery, turn black/grey with ae
yeast colonies on brain-heart infusion agar + 5% blood at 37C in 5-7% CO2 for 3-5 d. Soft and white to cream colored
Sporotrichosis- treatment
Iodide
Azole compounds
Cats v sensitive to iodine so itraconazole recommended
Sporotrichosis- zoonotic potential
Cats shed fungi in their lesions exudates and feces
Most human cases occur through contact with cat (scratch, bite). small wounds serve as portal of entry
Lymphocutaneous sporotrichosis
Prophylaxis: care in handling rote wood, plant material, and infected animals
Epizootic lymphangitis general
Histoplasma capsulatum var. farciminosum
Thermally dimorphic fungus
-yeast 37C: pear shaped, double contoured budding yeasts in macrophages or neutrophiles
-mold 25C: requires 8 w to grow in lab
Isolated from soil enriched with bird or bat faeces
Epizootic lymphangitis
Infection probably acquired by wound infection or transmission by bloodsucking insects
Disease of equidae; limited to north africa, europe, india, russiea
Granulomatous, nodular lesions with a tendency to ulcerate in skin, subq tissue, along lymphatic vessels
Chromoblastomycosis
Disease associated with dematiaceous fungi
Phialophora spp, Fonsecaea spp, Exophiala spp, Cladophialophora spp
Rare, chronic fungal infection in cats and humans with traumatic implantation of fungi in cutaneous and subq tissues
Dematiaceous fungi form thick-walled muriform cells- sclerotic bodies
CS: firm, protuberance, warty, ulcerative nodules (on feet and legs)
Eumycotic mycetoma
Disease associated with dematiaceous fungi
Bipolaris spp, Curvularia spp, Pseudallescheria spp
Rare. Reported in humans too
Limited to one area of body
Triad of CS: swelling, fistulas, grains or granules (aggregates of mycelium) in exudate
CS: subq swwlings with draining tracts and may resemble a chronic non healing abscess
Fistulous tumor: fistulas heal, tissue fibrosis occurs -> hard tumor like masses =chronic mycetomas
May penetrate the periosteum and cause osteomyelitis
Phaeohyphomycosis
Disease associated with dematiaceous fungi
Numerous fungi: Alternaria, Bipolaris, Cladophialophora, Curvularia, Phialophora, Exophiala, Phaeocremonium spp
Saprophytic, pigmented fungi that appear in lesions as dermaticeous, septate hyphal forms (no granules)
Dogs and cars
CS: pustules, abscesses, granulomas, shallow ulcerated or open lesions
Bovine nasal granuloa
Disease associated with dematiaceous fungi
Curvularia and Bipolaris spp
Granulomatous swellings in the nasal cavity and trachea of cattle
CS: dyspnea, inspiratory stridor, nasal discarge
Pinkish white polyps visible on endoscopy
Dx: direct exam of crushed polyp -> dematiaceous fungi
Culture: white colonies that become floccose, olive green, brown, or black with dark reverse pigment
Systemic mycoses- general characteristics
Systemic infections inherently virulent
Unique biochemical and morphological features enable them to evade host defenses and cause systemic disease
-three thermally dimorphic fungi
-cryptococcus neoformans is a yeast
Primary SOI: lungs
In most cases, respiratory infection is asymptomatic, resolves rapidly, and confers resistance to reinfection
Each agent exhibits unique pattern of secondary organ involvement
Restricted to geographic regions
Blastomycosis
Blastomyces dermatitidis
Humans, dogs, cats,
Blastomycosis- lesions
Few to numerous, variable sized, irregular, firm, grey to yellow areas of pulmonary consolidation and nodules in lungs and thoracic lymph nodes
Dissemination may result in nodular lesions in various organs but esp skin eyes bone
Cutaneous lesions are single or multiple papules or chronic, draining, nodular pyogranulomas
Lungs -> skin, eyes, bone
Blastomycosis- pathogenesis
Aerosolized mycelial fragments or spores from environment inhaled
Deposited in alveoli of susceptible host
Mature yeast develop at 37C
Grows intra and extra cellularly as large budding yeasts
May spread from lungs via lymphatics and/or blood to a variety of tissues (skin, eyes, bone)
Blastomycosis- distribution
Present worldwide
High endemic in NA
River basins, soil rich in decaying veg/acidic
Blastomycosis- CS
Acute pulmonary phase may be subclinical or self limiting, but if progresses, pyogranulomatous inflammation develops in lungs and other sites
CS:
coughing, dyspnea, dry and harsh lung sounds (85%)
Anorexia
Depression
Lameness (25%)
Lymphadenopathy (50%)
Skin lesions (50%): proliferative granulomas and subq abscesses that ulcerate and drain a serosanguineous discharge. Pronounced in cats
Ocular manifestations observed in 30-40% of dogs with systemic infection and include coneal opacity, uveitis, conjunctivitis, blindness
Blastomycosis- diagnosis
CS and history
Samples: tissues, tracheal washes, lymph node aspirates or biopsies, cutaneous lesion exudates or biopsies -> demonstration of characteristic yeast forms
Microscopy: spherical, thick-walled, large, broad-based budding yeast cells
Culture
Blastomycosis- diagnosis- cultures
often not necessary as yeast plentiful and characteristic in tissue
Cultures of Blastomyces dermatitidis= severe biohazard
Dimorphic fungus:
-room temp- mold characterized by hyline hyphae and development of spherical conidia that appear as balloons on short stalks
-37C- typical yeast- spherical, broad-based with thick cell wall
Blastomycosis- treatment/ zoonosis
Itraconazole
Amphotericin B lipid complex has been used to treat blastomycosis in dogs: effective; tx of choice in fulminating cases
Zoonotic transmission uncommon
Inoculation of subq tissues via contaminated necropsy knives or dog bites
Coccidioidomycosis
San Joaquin Valley Fever
Coccidioides immitis- v virulent
Dust borne non contagious infections
Humans and many animal species affected ( dogs, llamas, horses)
Coccidioidmycosis primarily a chronic respiratory disease, but canine infections disseminate to many tissues
Lungs -> eyes, bones, joints
Coccidioidomycosis- pathogenesis
Arthroconidia in environment mature into mycelia -> fragment into arthrospores -> inhalation by host
Mold to spherule transition (1-7 days) occurs in susceptible host at 37C
Spherule matures with production of endospores that are released in vivo
Infection may be localized to foci within lung, may extend to lymph nodes, or may disseminate
Tissues most often infected via dissemination: eyes, joints, bones
High rates of infection in dogs may be related to high propensity to sniff and dig soil
Coccidioidomycosis Distribution
Infections limited to arid and semi arid regions of southwestern USA, mexico, south america
Coccidioidomycosis- CS
Anorexia cough weight loss lameness abscess draining tracts lymphadenopathy meningitis intermittent diarrhea
Coccidioidomycosis- Dx
CS and history
Samples: draining lesions and biopsies or fine-needle aspirates of infected tissue -> demonstration of characteristic spherules
Large spherules with thick walls containing round endospores
Mycelial form of this organism is extremely dangerous to handle -> send to reference lab to culture
Dimorphic fungus but difficult to demonstrat dimorphism
Room temp- 37C mold characterized by hyaline hyphae and development of alternating barrel shaped arthroconidia
Coccidioidomycosis- Tx and zoonosis
Long term Tx (8-12 w) with azoles
eventually amphotericin B
Not considered contagious- no zoonotic potential
Beware- can develop mycelial phase on bandages of draining lesions
Histoplasmosis
World wide distributin
Chronic, non contagious, disseminated, granulomatous disease of humans and animals
Mainly in dogs and cars (under age of 4)
Histoplasmosis- lesions
Enlargement of liver, spleen, mesenteric lymph nodes
Ascites
Yellow white, variable sized nodules in lungs, enlargement of bronchial lymph nodes
Foci of granulomatous inflammation on liver, myocardium and small intestine
Histoplasmosis- pathogenesis
Inhalation or ingestion of microconidia or hyphal fragment from environment
Conversion to yeast phase in vivo
replication of yeast in monocytic cells
May spread from lungs to lymphatics or blood to a variety of tissues including spleen, bone marrow
Characteristic lesions are granulomatous
Histoplasmosis- distribution
Saprophytic fungus growing well in humid environments with highly nitrogenous soils (contaminated with bird/bat droppings)
Areas of high risk exposure: starling and blackbird roosting areas, old chicken houses, bat caves
Histoplasmosis- CS
Pulmonary infection predominant but disseminated infections commone
Chronic disease: inappetence, weight loss, fever, poor response to antibiotic therapy
Enlarged lymph nodes
In dogs: GI tract involvement
Anemia: due to bone marrow involvement and or GI blood loss
Histoplasmosis: Dx
CS and history
Samples: buffy coat smears, lymph node aspirates, rectal scrapings, biopsies, bone marrow aspirates
Small yeast cells within macrophages, Round yeast with basophilic center and clear halo
Histoplasmosis- Dx cultures
Cultures = severe biohazard
Dimorphic fungus:
-room temp: mold characterized by hyaline hyphae and development of microconidia and large, thick-walled tuberculate macroconidia
-37C: small (3-4um) budding yeast cells
Histoplasmosis- Tx and zoonosis
Long term tx (4-6 months) with azoles
Amphotericin B in combo with oral azole drug for several diseases
Not contagious, yeast form in tissues not easily ingections
Reported risk of infection via inhalation of dust contaminated by bird and bat faeces
Blastomyces dermatitidis- ecology
Slightly acidic soils and wood
Possible association with animal excreta
Water sources
Beaver dams
Blastomyces dermatitidis- saprobic form
Hyphae,
oval to pyriform terminal and lateral conidia
2-10 um in diameter
Blastomyces dermatitidis- parasitic form
Un-encapsulated yeasts with thick refractile double walls
5-20 um diameter
Coccidioides immitis- ecology
Alkaline desert soils with high levels of salt and carbonized organic materials
Coccidioides immitis- saprobic form
Hyphae with thick-walled or barrel-shaped arthroconidia alternating with thin-walled empty cells
Coccidioides immitis- parasitic form
Spherules
10-100 um in diameter
doubly refractile cell walls and containing endospores, 2-5 um diameter
Histoplasma capsulatum- ecology
Humid environments with hight nitrogenous soils
Esp those contaminated with bird or bat droppings
Histoplasma capsulatum- saprobic form
Hyphae, globose microconidia and tuberculate and non tuberculate macro conidia
8-16 um diameter
Histoplasma capsulatum- parasitic form
Tiny ovoid budding yeasts with narrow bases
2-4 um diameter
Cryptococcosis
Cryptococcus neoformans- capsulated yeast
Most common in cats
Reservoir: soil with pigeon excreta
Not considered contagious but acquired from environment
Dogs: disseminated form more common with CNS signs
Cryptococcosis- cats
Sneezing, labored breathing, nasal discharge, hard nodular skin swellings (most often over nose bridge), skin lesions on head, swollen LNs, lethargy and loss of appetite Distortion of nasal cavity as result of bone invasion Neurologic abnormalities (seizures, incoordination, behavioral changes) Eye disorders (chorioretinitis=inflammation of choroid and retina of the eye)
Cryptococcosis- Pathogenesis
Remains in yeast form in both environment and host
Inhalation of un-encapsulated yeast cells from environment-> capsulation of yeast in vivo
Nasal mucosa is site of most primary infections
Lesions range from gelatinous mass to granulomatous
Cryptococcosis- diagnosis
CS
Impression smears of exudate or granulomatous tissue (KOH preparations or india ink preparations on CSF)
Culture from biopsy, CSF, exudate: easily cultured with growth of capsulated yeast at 37C
Cryptococcosis- Tx and zoonotic potential
Surgical intervention
cryotherapy
Antifungals: azoles derivatives
Zoonotic potential low- risk of inhaling from same source as pet
Immunocompromised individuals at risk
Candidiasis
Candida albicans
Normal inhabitant of the nasopharynx, GI tract, external genitalia of many animal spp
Opportunistic infection, with localized mucocutaneous disease
Birds most frequently infected
Candidiasis- factors associated
Disruption of mucosal integrity
Indwelling, intravenous, or urinary catheters
Administration of antibiotics
Immunosuppressive drugs or diseases
Thrush, Crop mycosis, Sour crop
Candidiasis in birds; young more susceptible
Infrequently shallow ulcers and sloughing of necrotic epithelium may be present
Thrush, Crop mycosis, Sour crop- lesions
most frequently in crop
Thickened mucosa
whitish, raised pseudomembranes
Thrush, Crop mycosis, Sour crop- CS
Listelessness
Inappetence
Thrush, Crop mycosis, Sour crop- Tx, control, prevention
Nystatin and fluconazole
Improve sanitation
Minimizing AB use
Candidiasis in other species
Cutaneous candidiasis- rare in dogs and cats
Dogs: exfoliative dermatitis on muzzle, inguinal area, scrotum, and dorsal and lateral aspects of feed
Foxhounds: otitis externa
Gastrointestinal candidiasis with gastric ulceration (foals and calves)
Cutaneous and mucocutaneous candidiasis (pigs)
Candidiasis- Dx
Microscopic examination of scrapings or biopsy specimens from mucocutaneous lesions
-ovoid, budding yeast cells with thin walls
-psudohyphae or true hyphae
Culturing: white to cream colored, smooth, glaborous and yeast-like colonies on SDA
Germ tube test: presumptive differentiation of C albicans from other spp
Placing several colonies in animal serum - incubate at 37C for 3h - microscopic examination reveals short germ tubes
Biochemical tests (conventional or commercially available) and molecular tests
Aspergillosis
esp A fumigatus and A terreus
Worldwides
Primarily a respiratory infection- predilection between tissue varies between spp
Aspergillosis- most common forms
Pulmonary infections in poultry and other birds
Mycotic abortion in cattle
Guttural pouch mycosis in horses
Infections in the nasal and paranasal tissues, intervertebral sites and kidneys of dogs
Pulmonary and intestinal forms in cats
Aspergillosis- in birds
Primarily bronchopulmonary
-dyspnea, gasping, polypnea
-syrinx involved- change in voice
Food flicking, somnolence, anorexia, emaciation
Torticollis and disturbances of equilibrium (dissemination into brain)
Yellow nodules of varying sizes and consistency or plaque lesions are found in respiratory passages, lungs, air sacs, or membranes of body cavities
Spores can penetrate fresh or incubating eggs and will kill embryo
Aspergillosis- in ruminants
May be asymptomatic, appear in bronchopulmonary form, or cause placentitis and abortion
Mycotic pneumondia (may be rapidly fatal)
- signs include pyrexia, rapid shallow, stertorous respiration, nasal discharge, moist cough
Lungs are firm, heavy, mottled, do not collapse
Subacute to chronic mycotic pneumonia, lungs contain multiple discrete granulomas
Aspergillosis- Bovine mycotic abortion
Dead fetus aborted at 6-9 m gestation, and fetal membranes retained
Lesion in uterus, fetal membranes and often fetal skin
Uterus: intercaruncular areas thickened, leathery, dark red to tan, contain elevated or eroded foci covered by yellow/gray adherent pseudomembrane
Maternal caruncles- dark red to brown and adherent fetal cotyledons are makedly thickened
Cutaneous lesions in aborted fetuses consist of soft, red to gray, elevated, discrete foci that resemble ringworm
Aspergillosis- horses
Guttural pouch mycosis
Mycotic plaques in guttural pouch- located in caudodorsal aspect of medial pouch, over ICA
CS arise from damage to cranial nerves and arteries within mucosal lining of pouch- epistaxis
Hemorrhage is spontaneous and severe- repeated bouts may precede a fatal hemorrhagic episode
Dx: endoscopic exam of pouch
Tx: topical and systemic antifungal- based on sensitivity tests
If mild and affecting certain nerves, horse might recover
If severe, esp if affecting nerves involved with swallowing or with respiration, recovery is slim
Aspergillosis- in dogs
Canine nasal aspergillosis
Mucosa of nasal and paranasal sinuses may be covered by layer of grey-black necrotic material and fungal growth
Mucosa and underlying bone may be necrotic with loss of bone definition on radiographs
CS: lethargy
sneezing, nasal pain, ulceration of nares
Unilateral or bilateral sanguinopurulent discharge
Frontal sinus osteomyelitis and epistaxis
Aspergillosis- in dogs Dx
CS
rhinoscopy: presence of fungal plaques
Biopsy for histopathology or cytology and culture
Radiology
Aspergillosis- Dx
Ubiquitous and common fungus!
Microscopy of tissue samples- wet mounts using KOH
-hyaline, septate hyphae that branch dichotomously with a 45 angle
-characteristic conidial arrangement
Aspergillosis- tx and zoonotic potential
Topical azole delivered as a 1 hour infusion
Nasal asperigillosis in dogs: administration of itraconazole through tubes inserted surgically in frontal sinus (+ systemic tx with fluconazole or voriconazole- 6-8wks)
Note: oral and systemic antifungal therapy is used infrequently due to toxicity and excessive cost
Zoonotic potential: immunosuppressed individuals at risk
Pneumocystic pneumonia
Pneumocystis jirovecii (P carninii) Most common in horses CS: cough dyspnea exercise intolerance
Pneumocystic pneumonia-Dx
Cytological exam of fine-needle aspirates of lung biopsy or bronchoalveolar lavage
Organisms are small and may exist in low numbers
Wright-Giemsa stains best demonstrate trophozoites and intracystic bodies
-trophozoites- basophilic, dense, oval, irregular structures having a lobed surface and a single nucleus
-intracystic bodies- aggregates of spherical to oval dense basophilic structures against thick foamy background
Gomori methenamine silver stains the cyst form: commas in alveolar exudates is confirmatory
Pythiosis
Pythium insidiosum (lack chitin and ergosterol)
Fungal-like organism that are associated with water
Mostly seen in Gulf coast states
Sp most commonly affected are horses ad dogs
Chronic granulomatous disease
Equine Pythiosis, Bursatti, Swamp cancer, leeches
Cutaneous and subcutaneous mycosis in horses
Chronic granulomatous, ulcerative lesions or limbs and ventral abdomen
Lesions: pruritic discharge mucosinguineous exudate and often self-traumatized
-contain kunkers or leeched which are irregular yellowish concentrations that form in sinus tracts
Equine Pythiosis, Bursatti, Swamp cancer, leeches- Dx, Tx
direct examination and histopathology
Pythium insidiosum appears as large, hyaline nonseptate hyphae
Culture, PCR, ELISA
Tx: response to therapy is poor
Radical excision best if possible
Immunotherapy using sonicated extracts of agent
Canine pythiosis
Cutaneous, subcutaneous and GI disease in dogs
mainly seen as in infiltrative, pyogranulomatous enteritis; however subcutaneous lesions do occur
Poor prognosis surgical excision best chance
No zoonotic potential
