Fungal Infections Flashcards
1
Q
What do fungal PAMPs activate?
A
TLRs
- esp. TLR 2 and 4 for dermatophytes
NOD-like
C-type lectins (ex. mannose binding lectin)
- Dectin-1 binds to b-glucans and triggers IL-22/23
- Dectin-2 bind to α-mannans
- Dectin is on on mast cells too
Scavenger receptors
- DC-SIGN binds mannose
Malassezia cell wall carbohydrates are IgE binding epitopes with AD
- also have IgG and IgA produced (increased with more organisms)
2
Q
What type of immune response is most important for destroying established fungal infections?
A
Th1
Th17 - esp for dermatophytosis and Malassezia
no correlation between circulating Abs and protection for dermatophytes
- believed cell-mediated immune response is most important
3
Q
What are the predominant fungal genera identified on the skin surface of dogs?
A
Alternaria
Cladosporium
Epicoccum
variable proportions of Malassezia spp
- Malassezia globosa
- Malassezia restricta
- Malassezia pachydermatis (overgrows in inflamed skin)
4
Q
What are the predominant fungal genera identified on the skin surface of cats?
A
Cladosporium
Alternaria
Epicoccum
5
Q
What are the predominant fungal genera identified on the skin surface of horses?
A
Alternaria
Cladosporium
Fusarium
Aspergillus
Penicillium
Scopulariopsis
(many represent repeated transient contamination from the saprophytes)
6
Q
Which breeds of cats have higher carriage rates of Malassezia spp, even in the absence of skin lesions?
A
Devon Rex and Sphynx cats
7
Q
What is thought to be a primary reason for the increased number of fungal infections, especially opportunistic infections, in veterinary medicine?
A
higher number of immunosuppressed individuals being treated for cutaneous or systemic immune-mediated diseases or receiving chemotherapy treatment
8
Q
What are the two stains most commonly used to identify fungus?
A
periodic acid-Schiff (PAS) reaction
- bright magenta hue
- will only identify living fungus
Grocott’s methenamine silver (GMS) stain
- black color
- more sensitive and will identify more things (including nonviable)
(Fungal cell walls contain polysaccharides that form aldehyde groups upon oxidation and can be detected by both stains)
9
Q
If a fungal organism is cultured from the skin, what is important to confirm the pathogenic significance of the fungi?
A
fungal elements identified in the tissue
10
Q
What are the typical histopathologic morphologic features of Malassezia?
A
3–8 μm peanut-shaped yeast
Located in superficial keratin and follicular ostia
PAS can be helpful
11
Q
What are the typical histopathologic morphologic features of Candida?
A
can grow as yeasts, hyphae, and pseudohyphae simultaneously
3–4 μm ovoid yeast with single budding
Ellipsoid pseudohyphae with constriction at septae
Parallel-walled hyphae with regular septation
PAS can be helpful
12
Q
What are the typical histopathologic morphologic features of dermatophytes?
A
2–3 μm wavy septate hyphae with parallel walls
2 μm arthrospores
Endothrix (inside) or ectothrix (outside/degrade cuticle)
- most geophiles and zoophiles are ectothrix
- most anthropophiles are endothrix
Can cause deep pseudomycetomas in Persian cats
PAS or GMS can be helpful
13
Q
What are the typical histopathologic morphologic features of white-grain eumycotic mycetoma?
A
2–7 μm septate and nonpigmented hyphae
Infrequent dichotomous branching
Frequent 2–7 μm terminal cystic dilations
14
Q
What are the typical histopathologic morphologic features of black-grain eumycotic mycetoma?
A
2–7 μm septate and pigmented hyphae
Infrequent dichotomous branching
Frequent 2–7 μm terminal cystic dilations
15
Q
What are the typical histopathologic morphologic features of hyalohyphomycosis?
A
2–6 μm septate hyphae with parallel walls, occasional acute-angle branching
Up to 10 μm terminal bulbous swellings
4–12 μm yeast-like cells may be the only form
16
Q
What are the typical histopathologic morphologic features of Aspergillus spp?
A
2–6 μm septate hyphae with parallel walls
Frequent acute-angle branching
17
Q
What are the typical histopathologic morphologic features of mucorales?
A
Sparsely septate, 8–20 μm hyphae
Nonparallel walls and irregular branching
18
Q
What are the typical histopathologic morphologic features of entomophthoromycosis?
A
6–20 μm (Basidiobolus), 5–12 μm (Conidiobolus) hyphae, sparsely septate
Nonparallel walls, rare irregular branching, terminal bulbous dilations
Eosinophilic sleeve around hyphae
19
Q
What are the typical histopathologic morphologic features of phaeohyphomycosis?
A
2–10 μm pigmented hyphae ± branching with beaded appearance
4–15 or rarely 30–50 μm yeast-like forms
Fontana-Masson may highlight melanin
20
Q
What are the typical histopathologic morphologic features of chromoblastomycosis?
A
10–20 μm pigmented Medlar bodies with transverse and longitudinal septation
21
Q
What are the typical histopathologic morphologic features of oomycosis?
A
2–7 μm (Pythium) or 8–25 μm (Lagenidium)
Nonparallel walls, irregular branching, rare septae
Eosinophilic sleeve around hyphae
Will not stain with PAS
22
Q
What are the typical histopathologic morphologic features of Blastomyces spp?
A
5–20 μm yeast
Double contoured wall
Broad-based budding
Yeasts are typically sparse
23
Q
What are the typical histopathologic morphologic features of Histoplasma spp?
A
2–4 μm, round yeast
Clear halo, thin cell wall
Numerous yeasts within macrophages
GMS preferred over PAS
24
Q
What are the typical histopathologic morphologic features of Cryptococcus neoformans and Cryptococcus gattii?
A
3.5–20 μm, oval yeast
Wide clear capsule resembling a “soap bubble”
Cutaneous lesions common in facial/nasal region (especially in cats)
Yeasts are typically numerous
Capsule highlighted by mucicarmine (or Alcian blue)
25
What are the typical histopathologic morphologic features of Coccidioides immitis and Coccidioides posadasii?
20–80 μm spherules containing 2–5 μm endospores
Double contoured wall
Lesions typically distributed over bone infection sites
Spherules may be sparse
26
What are the typical histopathologic morphologic features of Sporothrix spp?
3–10 μm long and 1–2 μm diameter, elongated or “cigar-shaped” yeasts
Yeasts are numerous and commonly in macrophages
Lesions typically on head/neck (especially in cats)
27
What is the ecological niche of Malassezia species?
lipophilic fungi
- have a low carbohydrate-degrading capacity
- reduction of glycosyl hydrolase-encoding genes
- lack of a fatty acid synthase gene (can't make long chain fatty acids)
- concomitant expansion of lipid hydrolysing enzymes
live almost exclusively on skin/mucosal sites of warm-blooded vertebrates
28
What phylum does Malassezia belong to?
Basidiomycota
29
What species of Malassezia are most relevant for medical dermatology?
M. pachydermatis
M. globosa
M. sympodialis
M.restricta
M. furfur
M. nana - most common in cats esp ear canal
M. slooffiae - common in cats esp claw folds
30
What enzymes allow Malassezia yeasts to collect and use fatty acids from the skin or mucosal surfaces of their hosts?
lipases
phospholipases
acid sphingomyelinases
31
Which culture media is best for Malassezia?
lipid-enriched media such as modified Dixon’s agar
M. pachydermatis can grow on Sabouraud’s dextrose agar
- uniquely able to utilize lipid fractions in it
- doesn't prefer it though
32
Using cytologic techniques, which anatomical locations in healthy (non-Basset hound) dogs are reported to have the highest numbers of Malassezia yeasts?
peri-oral/ lip region
interdigital skin
perianal skin and anal mucosa
(less common in axillae, inguinal, and dorsum)
(Basset hounds have more pretty much everywhere)
33
What are some virulence attributes of Malassezia species?
Cell wall morphology
- thick
- spiral
- composition
Adherence to corneocytes
- small family of proteins anchored to plasma membrane
- can modulate cytokines and chemokines
Wide expansion of lipase and phospholipase gene
- might act in synergism with biofilm formation
Biofilm formation
Malassezia antigens appear to be resistant to lysis by NK cells
34
What dog breeds are at increased risk of Malassezia dermatitis?
West Highland white terriers
English setters
shih tzus
basset hounds
American cocker spaniels
boxers
dachshunds
poodles
Australian silky terriers
Newfoundland
35
What is a risk factor for Malassezia dermatitis in dogs?
presence of skin folds
hypersensitivity disorders
cornification defects
endocrinopathies
36
What is a risk factor for Malassezia dermatitis in cats?
hypersensitivity disorder
visceral neoplasia
other serious internal disease
37
Which molecular techniques allow for accurate identification of fungal species and recognition of genotypes that may have relevance for host-adaptation and virulence?
sequencing of:
- D1/D2 domain of the large subunit of the rRNA gene
- internal transcribed spacer (ITS)
- intergenic spacer (IGS)
- chitin synthase 2 (CHS2) gene
- ß-tubulin genes or regions
Multi-plex PCR (skin samples)
MALDI-TOF MS (from culture samples)
next generation sequencing
38
What hampers testing for resistance in Malassezia species in vitro?
unsuitability of the current CLSI and EUCAST reference methods
lack of an agreed modified protocol optimized for M. pachydermatis
absence of clinical breakpoints for either systemic or topical therapies
39
Which medications are recommended for treatment of Malassezia
Systemics
Azoles
- fluconazole may be varied
- resistance is reported
Terbinafine
- resistance has also been reported
Topicals
So many ones including essential oils and honey
Nystatin
- Wild type seens susceptible
- MIC might be increased in diseased states
3+% chlorhex (based in vivo)
topicals with azoles
40
What mutation in M. pachydermatis has been associated with azole resistance?
ERG11
gene that encodes lanosterol 14 –alpha-demethylase
target site for antifungal azoles
41
What are dermatophytes?
a distinct group of keratinolytic and keratinophilic fungi
possess a unique ability to digest keratin
allows them to colonize and infect keratinized tissues
42
What phylum do dermatophytes belong to?
Ascomycota
characterized by the formation of ascospores within specialized sac-like structures called asci
43
Malassezia overgrowth has been reported many species including cats, horses, cattle, and goats. What is the unifying feature of this condition in all species?
pruritus
44
What anatomical locations are most commonly affected with Malassezia dermatitis in cats and dogs?
ventral neck or abdomen, intertriginous regions, pinnae, feet, and skin folds
45
What anatomical locations are most commonly affected with Malassezia dermatitis in horses?
intertriginous
46
What are the histopathologic findings associated with Malassezia dermatitis?
moderate to marked epidermal hyperplasia
- involving the stratum spinosum
- to around 10 layers thick
- extending to the follicular infundibula
- scalloping/ “festooning” of the epidermal margin (not in cats)
mixed parakeratotic hyperkeratosis with mounds of keratin/crust
mixed dermatitis
- eosinophils and lymphocytes
- lymphocytic exocytosis of predominantly T lymphocytes
low sensitivity of histology compared with cytology
- approximately 30% of biopsies are falsely negative
- PAS can be helpful
47
Malassezia
48
Where are Candida spp frequently found in healthy animals?
gastrointestinal and urogenital tracts of both humans and domestic animals
49
What are infections with Candida spp associated with in domestic animals?
usually opportunistic and secondary to:
- immunosuppressive drug therapy
- systemic disease (ex. diabetes/Cushing's)
- prolonged antibiotic treatment
- young immunocompromised animals (esp pig or foals) = "thrush"
Vulvovaginal candidiasis due to synthetic progestogen in horses
50
What is are the clinical signs of a Candida spp infection?
pale, pseudomembranous plaques with ulcers on the tongue and gingiva
- Erosions/ulcers frequently covered by gray, malodorous exudate
can also affect oral mucocutaneous junction, distal extremities, perineum, vulva/scrotum, external ear canal, and intertriginous sites
pruritus is variable
51
What are the histopathologic findings associated with candidiasis?
large areas of superficial pustulation
- containing predominantly neutrophils
serocellular crust formation, spongiosis, and erosion to ulceration
organisms present in crusts or pustules
- yeasts, hyphae, and pseudohyphae
52
What order do dermatophytes belong in?
Onygenales
includes fungi that primarily infect keratinous substrates
53
What are the 7 currently accepted dermatophyte genera?
Trichophyton
Microsporum
Nannizzia
Epidermophyton
Paraphyton
Lophophyton
Arthroderma
54
What is the sexual form of a dermatophyte called?
teleomorph
produce ascospores which are more resistant in environment
*less common, mostly found in soil
55
What is the asexual form of a dermatophyte called?
anamorph
form spores such as (macro/micro)conidia or arthrospores
*most common
56
What are the 3 groups that dermatophytes are categorized into based on their environment?
anthropophilic (primarily living on humans)
- ex. T. rubrum
zoophilic (primarily living on animals)
- M. canis in dogs and cats
- T. verrucosum in livestock except pigs
- T. equinum in horses
geophilic (primarily living in the environment)
- ex M. gypseum/N. gypsea
57
What happens in the anamorph stage of dermatophytes?
introduction of spores to host -->
spores germinate and invade tissue -->
hyphae proliferate and produce enzymes to digest keratin -->
lesions form -->
produce spores through budding or hyphal fragmentation -->
spores are shed into the environment
58
Which animals are more prone to dermatophytosis?
Young animals with immature immune system
Geriatric animals with weakened immune response
Immunocompromised animals
59
What environmental factors can contribute to the development of dermatophytosis?
Overcrowding
Poor sanitation
Warm and humid environments
60
How are dermatophyte infections spread?
direct contact
- M. canis prefers this
fomites (including ectoparasites, environment, etc)
microtrauma significantly increases risk of development
- such as can be caused by ectoparasites
- laboratory settings need skin abrasion and moisture to cause infection
61
What is a defense mechanism against dermatophyte infections in cats?
normal grooming
62
What happens in the adherence step of the dermatophyte infection process?
occurs between 2–6 h after contact in M. canis
1) Arthroconidia adhere to keratinocytes through adhesins
- Subtilisin (Sub3) binds to host glycoproteins
- T. mentagrophytes protrudes fibrillar projections
2) Hydrophobic interactions enhance ability to stick
3) Protein-protein interactions occur
- Sub3 interacts with keratin and collagen
4) Enzymatic degradation
- Sub3, Sub4, and metalloprotease MEP3 degrade keratin
5) Signal transduction pathways in host and fungus
6) Cytoskeletal rearrangements in keratinocytes to allow closer contact
63
What does subtilisin (Sub3) in M. canis do?
is a serine protease
binds to glycoprotein receptors on the host's keratinocytes
- facilitates initial attachment
degrade surface glycoproteins
- exposes more binding sites
interacts with host proteins like keratin and collagen
degrades keratin and other structural proteins
64
What happens during the germination stage of a dermatophyte infection?
starts penetrating into skin
happens within 4 hours for T. mentagrophytes
arthroconidia increase in size and produce germ tubes
- extend horizontally and penetrate through the SC
leads to formation of hyphae and tissue invasion
secures the fungal structure and facilitates infection
65
What happens during the invasion stage of a dermatophyte infection?
hyphae penetrate the SC and grow in various directions
fungi begin producing arthrohyphae and invade keratinized tissues
form arthroconidia within seven days
66
How long does it typically take for lesions associated with dermatophyte infections to occur after exposure?
one to three weeks
67
How do dermatophytes degrade keratin?
produce sulfites to cleave cysteine bonds in keratin
- but high environmental cysteine levels are toxic
convert cysteine to sulfite via the enzyme cysteine dioxygenase (Cdo1)
sulfite efflux pump (Ssu1) helps secrete sulfite to keep cycle going
*both Cdo1 and Ssu1 are needed for dermatophytes to invade properly
68
What the primary enzymes (virulence factors) that dermatophytes have to degrade keratin?
Endoproteases (keratin to large peptides via peptide bonds)
- Subtilisins (Sub)
- Fungalysins-type metalloproteases (Mep)
Exoproteases (large peptides into smaller ones/amino acids)
- Leucine aminopeptidases (Lap)
- Dipeptidyl peptidases (Dpp)
69
What happens to the pH of skin during a dermatophyte infection?
amino acid metabolism causes an alkaline shift
70
What is the optimal pH for dermatophyte keratinases to be active at?
Early Infection Stages: slightly acidic environment
Later Infection Stages: higher, more alkaline pH levels
mediated by the conserved PacC/Pal signal pathway
71
How is the NLRP3 inflammasome activated in dermatophyte infections?
microbial binding to CLRs or TLRs -->
induces pro-IL-1β synthesis and NLRP3 transduction -->
- via NF-κB-dependent activation
various factors (cathepsin, K+ efflux, ROS) NLRP3 activation -->
leads to assembly of a complex with NLRP3, ASC, and pro-caspase-1
- facilitates pro-caspase-1 activation and processing of mature IL-1β
72
How do dermatophytes evade the immune system?
1) Secretion of Immunosuppressive Substances
- ex. mannans
2) Induction of Non-Effective Antibody Responses
- stimulate the production of unhelpful antibodies (ex. IgE)
3) Delayed-Type Hypersensitivity (DTH) Evasion
4) Activation of Host Signaling Pathways (allow spread/divert attention)
- ex. activate MAPK pathways in keratinocytes
5) Modulate Th17 Cells and C-type Lectin Receptors
6) keratin degradation enzymes
7) cysteine dioxygenze
8) cell wall components affecting complement inhibition
73
Which breed of cat and which breed of dog are predisposed to dermatophyte infections?
Persian cats
- may have worse infections
Yorkshire terriers
hunting dogs may be predisposed to geophilic infections
74
What is the difference between a kerion and a pseudomycetoma/mycetoma?
Kerion: Presents as a single or multiple erythematous, alopecic, dome-shaped, exudative nodule(s) with granuloma or pyogranuloma formation, often containing fungal spores
- usually have a good prognosis in dogs
- typically more superficial
Pseudomycetoma and Mycetoma: Characterized by nodules that fistulate, ulcerate, and drain serous to purulent debris and may contain grains
- prognosis is usually bad for cats and dogs
75
Why is green fluorescence under the Wood's lamp (320 and 400 nm wavelength) observed in M. canis infections?
a chemical metabolite in the cortex or medulla of the hair
- pteridine
can develop as early as 5-7 days post-infection (usually 10-14)
sensitivity ~71% and specificity ~ 92%
other species like M. distorum, M. audouinii, and T. schoenleinii do it too
- N. gypsea occasionally can
- T. verrucosum can in cattle
76
What culture media is used for grow dermatophytes?
dermatophyte test media (DTM)
- contains phenol red that changes color when pH increases
- gross colony and microscopic morphology can be altered
Sabouraud dextrose agar
- better colony morphology
- may not produce macroconidia --> switch to sporulation media
*usually contain cycloheximide to slow growth of contaminants
- interferes with the translocation step in protein synthesis
77
What species of dermatophyte is most common in cows, goats, sheep, and camelids?
T. verrucosum
78
What species of dermatophyte is most common in pigs?
Microsporum nanum (now Nannizzia nana)
79
What is a hypha?
A single vegetative filament of a fungus
80
What is a mycelium?
a mass of hyphae
81
What is the difference between septate, pauciseptate, and sparely septate?
septate if they have divisions between cells
- pauciseptate if hyphae have few septations
sparsely septate if they have many nuclei within a cell
82
What species of dermatophyte is most common in horses?
Trichophyton equinum
83
What are the pros and cons of culturing for dermatophytes?
Pros
- Low cost
- Easy to perform
- Can distinguish between species (with limitations)
Cons
- Requires expertise to determine species
- Can be contaminated by saprophytes
- takes days–weeks
84
What are the pros and cons of PCR for dermatophytes?
Pros
- Highly sensitive
- Can distinguish between species
- takes hours–days
Cons
- Unable to distinguish dead and alive fungi
*Negative PCR in a treated cat is compatible with cure
85
What are the pros and cons of ELISA for dermatophytes?
Pros
- Highly specific
- takes hours–days
Cons
- False positives due to past infections
86
What is the colony and conidia morphology of M. canis?
Colony: white to cream with reverse yellow pigment, cottony to wooly
Macroconidia: thick walled, spindle-shaped with 5-15 cells
87
Which common dermatophyte is this consistent with?
M. canis
88
Which common dermatophyte is this consistent with?
M. canis
89
Which common dermatophyte is this consistent with?
N. gypsea (M. gypseum)
90
What is the colony and conidia morphology of N. gypsea/M. gypseum?
Colony: cream to buff, yellowish reverse, suede-like to granular
Macroconidia: ellipsoidal, thin-walled, verrucose, four to six-celled
91
Which common dermatophyte is this consistent with?
N. gypsea (M. gypseum)
92
Which common dermatophyte is this consistent with?
T. mentagrophytes
93
What is the colony and conidia morphology of T. mentagrophytes?
Colony: white to cream, brown reverse, powdery to granular
Microconidia: numerous, hyaline, smooth-walled, spherical to pyriform
Less commonly can have
- Macroconidia: smooth, thin-walled, clavate-shaped
- spherical chlamydospores
- spiral hyphae
94
Which common dermatophyte is this consistent with?
T. mentagrophytes
95
What is special about culturing Trichophyton verrucosum?
All strains require thiamine
approximately 80% require thiamine and inositol
96
What is special about culturing Trichophyton equinum?
Most strains require nicotinic acid
97
What is the dermatoscopic finding associated with dermatophyte infections?
"comma hairs"
hyphae and spores on the shafts
98
How are dermatophyte infections treated?
Mild ones in immunocompetent individuals may be self-limiting
Azoles
- ketoconazole (may be less effective, not in horses or cats)
- itraconazole (on-label)
- fluconazole (highest MIC, poor efficacy)
Terbinafine
Griseofulvin
Topicals
- Lime sulfur
- enilconazole, clotrimazole, miconazole
- miconazole/chlorhexidine shampoos
Vaccinations in horses and cattle outside US
99
What are the histopathologic findings associated with superficial dermatophytosis?
Folliculitis and furunculosis
- predominantly pyogranulomatous with eosinophils
Acantholytic cells may be seen within follicles/follicular ostia
narrow, 2-3-μm diameter, pink, wavy, septate hyphae
- not very sensitive
- PAS or GMS can help
Orthokeratotic and parakeratotic hyperkeratosis with serocellular crusting
100
For which species of dermatophyte are hyphae most likely to only be found in the stratum corneum (for dogs)?
Trichophyton mentagrophytes and Microsporum persicolor
101
What are the histopathologic findings associated with dermatophytic kerions or pseudomycetomas?
Aggregates of refractile , pleomorphic fungal hyphae
- Tangled, “bubbly”
- Bulbous thick walled dilatations
Splendore Hoeppli phenomenon
(Pyo)granulomatous inflammation
Look for regular dermatophytes in hair shafts!
102
Dermatophytic kerion
103
Dermatophyte (inset is PAS)
104
Dermatophytic kerion (inset is PAS)
105
Dermatophyte with furunculosis
106
Dermatophyte with minimal folliculitis
107
Which medication is most highly associated with opportunistic fungal infections?
cyclosporine
108
Which fungal infections are German shepherd dogs prone to?
disseminated aspergillosis and hyalohyphomycosis
due to a suspected familial immunodeficiency
109
What does hyalohyphomycosis mean?
all opportunistic, non-dermatophytic fungal infections caused by saprophytic fungi that grow as nonpigmented hyphae in tissue
110
What does phaeohyphomycosis mean?
caused by pigmented dematiaceous fungi, which grow as hyphae and yeast-like cells
111
What does chromoblastomycosis mean?
are a subset of pigmented fungal infections
seen predominantly as large, rounded, thick-walled cells
- sclerotic bodies or Medlar bodies
most veterinary reports from amphibians or horses
112
What does chromomycosis mean?
largely historical term for phaeohyphomycosis and chromoblastomycosis combined
113
What are eumycotic mycetomas?
exhibit 3 characteristic features:
1) tumefaction
2) grains or granules within the exudate
- can be considered white or black
- represent large aggregates of the infectious organisms
3) a draining tract
- not always present
thought to be due to wound contamination or direct implantation
most commonly reported in subtropical to tropical climates
114
What is piedra?
asymptomatic fungal infection of the extrafollicular portion of the hair shaft
caused by:
- Piedraia hortae (“black piedra”)
- Trichosporon beigelii (“white piedra”)
most commonly seen in the temperate and subtropical climates
115
Piedra
116
What is the typical clinical presentation of eumycotic mycetomas?
usually solitary nodules +/- ulcer located on the distal limbs or face
- particularly the nostrils and lip commissures in horses
progressive fibrosis imparts a firm, tumor-like appearance
white-grain mycetomas in dogs are typically intraperitoneal
- possible connection to the body wall
- formation of draining tracts
117
What are the fungal species most frequently associated with white-grain mycetomas?
Pseudallescheria (Scedosporium) boydii
- most common overall in horses
Penicillium (Thermomyces) dupontii
118
What are the fungal species most frequently associated with black-grain mycetomas?
Curvularia lunata
Curvularia geniculata
Cladophialophora bantiana
Madurella spp.
119
How can hyphal contours be described cytomorphologically?
parallel
nonparallel
swollen
- including the “toruloid” (beaded)
120
How can hyphal branching be described cytomorphologically?
acute-angle, right-angle, or variable or haphazard
dichotomous
121
What are the histopathologic findings associated with eumycotic mycetomas?
(pyo)granulomatous dermatitis and panniculitis with fungal hyphae
central aggregates which comprise the clinically evident tissue grains
- pigmented or non-pigmented
+/- Splendore-Hoeppli reaction
zone of degenerate neutrophils, then macrophages
variable enclosing fibroplasia
122
What are chlamydoconidia?
terminal cystic dilations on hyphae
123
White-grain mycetoma
124
Black-grain mycetoma
125
What species are associated with hyalohyphomycoses?
*May overlap with white-grain mycetomas
Fusarium
Scedosporium
Penicillium
Acremonium
Chrysosporium
Geomyces
Lomentospora
Oxyporus
Paecilomyces
Rasamsonia
Talaromyces
Aspergillus (is conventionally not included)
126
In immunocompetent dogs, how do hyalohyphomycoses frequently manifest?
young adult, large-breed dogs
systemic disease similar to invasive aspergillosis
- osteomyelitis, discospondylitis, pneumonia, and/or visceral
127
In immunosuppressed dogs, how do hyalohyphomycosis frequently manifest?
presentation may appear similar to phaeohyphomycosis with nodular or ulcerated lesions limited to skin and subcutaneous tissue (often of distal extremities), or may reflect disseminated disease
128
129
In which fungal infections is hyphal invasion of blood vessels most common?
Mucorales or Aspergillus spp
sometimes hyalohyphomycoses
130
Which hyalohyphomycosis species can cause yeast in skin?
Fusarium
Paecilomyces
Scedosporium
(and others)
131
When nonviable, hyalohyphomycosis hyphae may appear negatively stained and pauciseptate, and may be confused with oomycetes. What histopathologic feature can help suggest one over the other?
prominent eosinophilic inflammation common in oomycete infection is not typical of hyalohyphomycosis
132
What are the morphologic features of Aspergillus species?
narrow, parallel-walled, regularly septate hyphae with acute-angle branching
- historically considered diagnostic but are not completely unique
- other hyaline molds may appear similar
- some Aspergillus species can have only yeast
pair with culture or PCR to know for sure
- is found widely in environment so culture and PCR aren't enough alone
133
Why can differentiation between hyalohyphomycosis and Aspergillus be important for treatment?
hyalohyphomycosis are inherently resistant to antifungal drugs (ex. itraconazole) that might initially be chosen to treat aspergillosis
134
What usually causes cutaneous infections with Aspergillus ?
extension of sinonasal or systemic disease
135
What is entomophthoromycosis?
a non-pigmented fungus but typically considered separately
caused by Conidiobolus spp and Basidiobolus spp
- part of the former Zygomycota phylum
common in subtropical to tropical climates
wound contamination or extension from GI/respiratory disease
- saprophytic soil fungus
136
What are the clinical lesions associated with Conidiobolus?
nodules on the external nares and within the nasal passages in horses, dogs, and rarely cats, resulting in nasal discharge, facial deformity, and exophthalmos with possible extension into adjacent skin or the brain
- C. coronatus = common infectious causes of rhinitis/sinusitis in horses
137
What are the clinical lesions associated with Basidiobolus ranarum?
solitary, large, ulcerative skin lesions on the head/neck/chest/trunk of horses
- pruritus is usually moderate to severe
- like pythium but doesn't have the "leeches"
can also cause ulcerative skin lesions in dogs resembling those of pythiosis
- in addition to GI and disseminated disease
138
What are Zygomycetes?
Recently reclassified so doesn't really exist
includes what are now entomophthoromycosis and mucormycosis
139
How can you tell entomophthoromycoses apart from oomycoses on histopathology?
GMS and PAS should highlight Conidiobolus and Basidiobolus spp
PAS typically does not stain the cell walls of oomycetes
140
What are the histopathologic findings associated with entomophthoromycoses?
*LOOKS VERY SIMILAR TO OOMYCETES*
Pyogranulomatous inflammation
Many eosinophils (not always!)
- Cores of degranulating/necrotic eos
- Splendore Hoeppli (“eosinophilic
Often fewer bugs than pythiosis
- not always present on cytology
GMS > PAS (but both work)
Hyphae
- Irregular branching, non-parallel, pauciseptate/sparsely septate
- ~5 20um width
- Basophilic or “hyphal ghosts”
- Non-dichotomous branching
141
What is the best culture media for most opportunistic fungi?
Sabouraud dextrose agar
-without cycloheximide
142
What is mucormycosis?
a non-pigmented fungus but typically considered separately
caused by fungi of the order Mucorales
- part of the former Zygomycota phylum
- includes Rhizopus, Rhizomucor, Absidia, Saksenaea, Cokeromyces
cutaneous infection in dogs and cats is very rare
more likely to cause systemic disease
143
Which fungal species are most commonly associated with phaeohyphomycosis?
*May overlap with black-grain mycetomas
Alternaria
Bipolaris
Cladophialophora
Curvularia
Exophiala
Fonsecaea
144
Where are the clinical lesions associated with phaeohyphomycoses?
nodules predominantly on nose and digits
- areas more frequently in contact with soil
- lesions result from wound contamination
hyphae may be dense/pigmented enough resemble melanoma
more likely to be disseminated in immunosuppressed animals
145
What are the histopathologic findings associated with phaeohyphomycoses?
(pyo)granulomatous inflammation
- without significant numbers of eosinophils
hyphae commonly have a toruloid, or beaded, appearance
- are seen both extracellularly and within macrophages
-fungi may be poorly or not visibly pigmented on H&E
- Fontana-Masson stain can highlight melanin
146
phaeohyphomycosis
fungal melanin appears as greenish with Romanowsky stain
147
Can presence of melanin on culture be used to differentiate between phaeo- and hyalohyphomycoses?
No
melanin contributes fungal survival in diverse hostile environments
- believed to contribute to fungal virulence
- interact with electromagnetic radiation frequencies
- also important for other aspects of survival
also in some bacteria and helminths
148
How doe the primary components of the cell wall/membrane and reproduction differ between oomycetes and true fungi?
Cell wall
- oomycetes have cellulose rather than chitin
Cell membrane
- oomycetes have β-glucan rather than ergosterol
oomycetes produce (aquatic) motile flagellate zoospores
149
What do P. insidiosum zoospores have a special tropism towards?
animal hair, wounds, damaged skin, intestinal mucosa, and plant leaves
150
What happens when oomycete zoospores come in contact with non-intact tissue?
Zoospores encyst on the non-intact tissues -->
secrete amorphous glycoprotein, facilitating adhesion -->
develop germ tubes in direction of tissue -->
tissue invasion
151
What are “kunkers” or "leeches"?
yellow-gray, hard concretions composed of necrotic debris with myriads of filamentous hyaline hyphae seen with Pythium in horses
- "coral-like" grains
152
Which oomycete is most associated with lymphadenopathy, dissemination including pulmonary nodules, and vessel invasion?
Lagenidium giganteum (forma caninum)
153
Which oomycete is most associated with gastrointestinal disease?
Pythium insidiosum
154
Which oomycete is associated with slower disease progression and a more favorable prognosis?
Paralagenidium karlingii
155
Oomycete
156
What are the histopathologic findings associated with oomycete infections?
eosinophilic, (pyo)granulomatous inflammation
with fibrosis, multifocal necrosis, and sometimes vasculitis
hyphae
- Negatively stained
- Irregular, non parallel, pauciseptate
- ~5-25um width (Lagenidium tends to be largest)
- Non dichotomous branching
stain with GMS
don't stain well with PAS due to lack of chitin
- of them, Pythium is more likely to be mildly PAS positive
157
What time of year and in which geographical location are oomycete infections typically seen?
summer and fall in tropical and subtropical areas of the world
- have been reported in northeast coast, midwest, and north CA
158
How can you diagnose an oomycete infection?
PCR or indirect immunoperoxidase for Pythium antigen
Pythium ELISA (not great for other species)
Culture
- kunkers are best if present (as are grains from mycetomas)
- false positives are likely if refrigerated
Histopathology
159
What are germ tubes?
Tube-like structures produced by germinatingspores or yeast cells. These can develop into hyphae, asin C. albicans
160
What are chlamydospores?
Thick-walled, resistant spores formed by differentiation of hyphae or pseudohyphae, as seen in C. albicans and Histoplasma capsulatum
161
Which dimorphic fungus is a facultative intracellular pathogen?
Histoplasma capsulatum
162
What is the most common species of Cryptococcus that are reported to cause illness in veterinary medicine?
Cryptococcus neoformans (var. neoformans and var. grubii)
- can be found in avian guano and decaying vegetation
- wide geographic distribution
Cryptococcus gattii
- associated with trees
- more restricted geographical regions (very west coast in US)
- color change on CGB Agar
163
Which breeds of cats are prone to cryptococcosis infections?
Siamese, Birman, Ragdoll, Abyssinian, and Himalayan breeds
164
Which breeds of dogs are prone to cryptococcosis infections?
GSDs, Doberman pinschers, Great Danes, Cocker spaniels
165
Which species are most commonly affected with cryptococcosis infections?
Cats > dogs, koalas (sentinel) > others
also reported in ferrets, horses, camelids, goats, sheep, cattle, dolphins, birds, other marsupials
166
How do animals tend to contract cryptococcosis infections and what happens following inoculation?
inhalation of the fungal blastospores/basidiospores -->
conversion to yeast form with capsule -->
upper respiratory involvement -->
- potential nasal deformity
- can spread to retina or CNS
- can have local extension onto skin
can spread to skin, lungs, salivary glands, middle ears, kidney, etc
167
What are the typical clinical signs associated with cryptococcosis infections?
upper respiratory involvement (43-90% of cases in cats)
- chronic sneezing
- nasal discharge
- nasal deformation +/- adjacent structures
can also commonly involve the retina, draining lymph nodes and CNS
single or multifocal ulcerated or nonulcerated cutaneous masses
- 31-41% of cases in cats
immunosuppression may be associate with degree of dissemination
dogs are more likely to have disseminated disease than cats
- present with non-specific signs
- less likely to have cutaneous involvement
direct inoculation may be more common in koalas
168
How is cryptococcosis diagnosed?
*antigen detection using latex agglutination assays
- serum, pleural or peritoneal effusions, urine, CSF
- higher sensitivity in cats than dogs (can't rule out in dogs)
tissue samples should be submitted for cytology, histology and culture
- grow in culture as a yeast rather than mold so less risk
- culture is actually recommended to determine susceptibility and type
169
What do cryptococcal yeasts look like on cytology?
encapsulated, spherical to oval yeasts, 4–10 μm, narrow-based budding
thick mucopolysaccharide capsule
- allows it to hide from the immune system
- can be visualized using India ink negative stains
170
Background is India ink.
Cryptococcus
171
What are the histopathologic findings associated with cryptococcus?
Typical little inflammation
- if present is mixed (macs, neuts, eos, L/P)
- exception: capsule deficient organisms, rare
Yeasts, typically numerous
- Round oval, “folded”
- 2-10µm diameter
- Thin walled
- Thick mucopolysaccharide capsule (up to 30 µ m thick)
--> “Soap bubble"
--> Mayer mucicarmine or Alcian blue will highlight the capsule
- Narrow based budding
172
Is immunosuppression strongly associated with dimorphic fungal infections?
No, disease frequently occurs in immunocompetent individuals
173
Cryptococcus
second inset is a mucicarmine stain highlighting the capsule
174
What is the the typical treatment and prognosis of cryptococcosis?
triazoles
- fluconazole > itraconazole due to CNS penetration
if bad, consider adding amphotericin B +/- flucytosine
usually at least 6 to 8 months of treatment is necessary
- may need to be treated for years
- treatment should be continued until the antigen titer is zero
prognosis is generally good but relapse can occur
- sometimes as long as 10 years later
FeLV likely has a negative impact on treatment outcomes
175
What mutation has been associated with fluconazole resistance in cryptococcosis?
ERG11
gene encoding for the azole target enzyme 14-α-demethylase
176
What is the most common species of Histoplasma that are reported to cause illness in veterinary medicine?
Histoplasma capsulatum
- endemic in central and eastern US
- mostly from guano of bats (also in decaying avian guano)
- traditional dimorphic clinical signs
Histoplasma farciminosum
- more common in/limited to horses
- mosquitos and flies may be a vector
- may be spread via fomites
- produces cutaneous to subcutaneous lymphatic nodules that rupture
- endemic in Africa, Asia, and Eastern Europe
177
Which breeds of cats are prone to histoplasmosis infections?
Persian cats may be slightly over-represented
178
Which breeds of dogs are prone to histoplasmosis infections?
Active hunting dogs (contact with soil/bat guano)
179
How do animals tend to contract histoplasmosis infections and what happens following inoculation?
inhalation of the fungal conidia from mycelium in soil -->
fungus transforms into a yeast phase in body -->
engulfed by phagocytic cells, primarily macrophages -->
- use heatshock proteins to help enter
- alter their cell wall to conceal b-glucans
dissemination of the yeasts via the blood and lymphatics -->
spreads to lymph nodes, liver, spleen, bone marrow, etc.
- primarily reproduces in lungs
- occasionally histo will reproduce just in GI tract of dogs
180
What is the primary (American) geographical range of histoplasmosis in dogs and cats?
Central and eastern US
- most in Ohio, Mississippi, and Missouri river valleys
- indoor-only cats have been reported to get it too
Central America
181
Which age of animals seems to be at highest risk of histoplasmosis?
Young to middle aged
Cats had a mean age of 4 to 9 years
182
What is the primary (American) geographical range of cryptococcosis in dogs and cats?
C. neoformans
- widespread
- indoor-only cats have been reported to get it too
C. gattii
- very west coast of US
183
Which species are most commonly affected with histoplasmosis infections?
Cats > dogs
H. farciminosum in horses
184
What are the typical clinical signs associated with histoplasmosis infections?
mostly non-specific and include:
- lethargy, anorexia/weight loss, fever, anemia, weakness, etc
dyspnea and tachypnea are common (cough is rare in cats)
- more common in cats
gastrointestinal disease (diarrhea, melena, hematochezia)
- more common in dogs
ocular signs (chorioretinitis, anterior uveitis, or retinal detachments)
can also cause hepatitis, lymphadenopathy, splenomegaly, lameness
can have multiple papules and nodules which may be ulcerated
- one cat had skin fragility/tearing
can cause hypercalcemia (and other labwork abnormalities)
185
How is histoplasmosis diagnosed?
*definitive diagnosis by cytologic or histopathologic identification
*antigen ELISA assay on serum or urine through MiraVista
- may cross react with other fungal pathogens (Blastomyces)
- can be used to help determine success of treatment
Abnormalities on thoracic radiographs are common
- can have a number of patterns, typically not large nodules
Occasionally seen on a peripheral blood smear
Ideally don't do a fungal culture
- grows in mycelium form so is hazard to laboratory workers
PCR
- not routinely used
186
What do Histoplasma yeasts look like on cytology?
2–4 μm in diameter with thin cell wall
surrounded by a 4 μm halo
usually reside within macrophages
may show narrow-based budding
187
Histoplasma
188
What are the histopathologic findings associated with histoplasmosis?
Granulomatous inflammation
Usually many yeasts
- Oval, round
- 2 5µm diameter
- 1-2µm center surrounded by halo (artifact)
- Narrow based budding
- Intracellular
GMS is better because PAS may only stain the nucleus
189
190
What is the the typical treatment and prognosis of histoplasmosis?
Dogs and cats: Itraconazole for a minimum of 4 to 6 months
- at least 2 months after resolution of clinical signs
- possibly until antigen assays are negative
- could try fluconazole but it may have lower efficacy/higher resistance
- posaconazole could be considered if don't do well with itra/flu
- if very sick, start with amphotericin B
- prognosis depends on extend of disease (survival = 66-100%)
Horses: strict hygiene, quarantine, and slaughter
- some undergo spontaneous remission
191
What is the most common species of Blastomyces that are reported to cause illness in veterinary medicine?
Blastomyces dermatitidis
- primarily in North America but also Africa, India, and Central America
- found in decaying vegetation or animal excreta
- in soil it grows as the mycelial form
192
What are the four elements that make up the “microfocus model” that helps explain where B. dermatitidis is most likely found?
moisture
soil type (sandy, acid)
presence of wildlife
soil disruption
193
What is the primary (American) geographical range of blastomycosis in dogs and cats?
mostly found in the eastern and southern parts of the USA
- Ohio, St. Lawrence, Missouri, and Mississippi River Valleys
- Great Lakes region
- New York and middle Atlantic states
- Quebec, Ontario, Manitoba, and Saskatchewan
194
Which species are most commonly affected with blastomycosis infections?
Dogs, humans > cats >> others
reported in horses, ferrets, sea lions, lemurs, monkeys, wolves, foxes, black bears, lions, cheetahs, snow leopards
195
How do animals tend to contract blastomycosis infections and what happens following inoculation?
inhalation of the fungal spores/conidia from mycelial phase in soil-->
fungus transforms into a yeast phase in body -->
primary location is in the lungs -->
organism may disseminate via the vascular or lymphatic system -->
spread to lymph nodes, eyes, skin, bones and brain
*occasional direct inoculation occurs but is rare
196
Which breeds of dogs are prone to blastomycosis infections?
Active hunting dogs (Coonhounds, Pointers and Weimaraners)
- usually young, male, large breed with outdoor access
197
Which breeds of cats are prone to blastomycosis infections?
Siamese, Abyssinian, and Havana Brown cats
- may have a predilection for young males (not consistent)
198
Do cats have to go outside to contract a dimorphic infection?
No
soil-borne fungi like Blasto, Histo, Crypto, Coccidio have been reported in indoor-only animals
199
What are the typical clinical signs associated with blastomycosis infections?
Most common signs are lethargy, weakness, fever, inappetence/weight loss
20-50% have lower respiratory signs (dyspnea, cough)
May have additional signs depending on where it has spread to
- cutaneous involvement in 22-63% of cats
- cats are more likely to get CNS signs
Skin lesions most common on the muzzle or distal limbs, paws, digits
can cause hypercalcemia
200
How is blastomycosis diagnosed?
Enzyme immunoassay antigen test from urine > serum
- through MiraVista
- tests for cell wall galactomannan
- high cross reactivity with histoplasmosis; less for coccidiomycosis
Thoracic radiographs
- nodular to diffuse pattern +/- pleural effusion
- “snowstorm pattern”
Fundic exam
Identification in tissue with cytology or histopathology
Ideally don't do a fungal culture
- Grows in mycelium form in the lab (very dangerous to lab personnel)
201
What do Blastomyces yeasts look like on cytology?
round to oval
10–20 μm in diameter
have a basophilic cytoplasm
thick and double-contoured walls
display broad-based budding
often blue/purple on Diff-Quik
202
What are the histopathologic findings associated with blastomycosis?
(Pyo)granulomatous inflammation primarily in dermis, subcutis
- can resist destruction by neutrophils
Yeasts usually only present in small numbers
- Round
- 5 30µm diameter
- Distinct double wall
- Granular protoplasm
- Broad based budding
- Usually extracellular, may be intracellular
203
Blastomyces
204
Blastomyces
205
What is the the typical treatment and prognosis of blastomycosis?
Itraconazole
- Fluconazole seems less effective but may be good if in CNS
- new azoles like posaconazole/voriconazole could be considered
+/- amphotericin B depending on severity
duration of treatment is debated
- at least 4 to 6 months (some 1+ yrs)
- maybe when you get 2 negative urine antigen tests 1 mo apart
Success depends on severity
- 25-50% of dogs will die
- ~25% of dogs will relapse within 6 months of stopping therapy
206
What is the most common species of Coccidioides that are reported to cause illness in veterinary medicine?
Coccidioides immitis and Coccidioides posadasii
- endemic in southwestern US (CA and AZ), Central and South America
- like sandy/alkaline soils, high temperature, low rainfall, and low elevation
207
208
Which species are most commonly affected with coccidiomycosis infections?
Dogs, humans > cats, south American camelids > horses
209
How do animals tend to contract coccidiomycosis infections and what happens following inoculation?
Soil gets moist which allows for fungal growth -->
there is a dry period -->
the soil is disturbed (including heavy rainfall, wind, droughts, etc) -->
arthrospores/arthroconidia are released and inhaled -->
- very few spores can cause disease
- minority of exposed patients develop clinical disease
phagocytosed by alveolar macrophages -->
transforms into spherules in the body -->
spherule ruptures, releasing endospores -->
cycle continues and disseminate when cannot be contained in lungs
210
How do cutaneous lesions associated with dimorphic infections occur?
Usually due to dissemination
Direct inoculation is more common with Sporotrix > Coccidioides
211
What are the typical clinical signs associated with coccidiomycosis infections?
Most patients present with a low-grade, chronic course of disease
- may have latent disease that reactivates with immunosuppression
Intermittent fever, lethargy, hyporexia, weight loss, chronic cough
- respiratory signs reported in only 25% of cats
Minority of patients present with disseminated disease
- clinical signs depend on where it has spread
- can have a tropism for bone (skin lesions can occur over this)
- skin lesions are more common in cats than dogs (56%)
- dogs can have pericarditis, effusion and right-sided heart failure
212
How is coccidiomycosis diagnosed?
*AGID assays for IgG and IgM antibodies
- IgM detection will occur 2-5 weeks after infection
- IgG occurs 8-12 weeks after infection
- No correlation between titer and severity of disease in dogs
- False negatives can occur
Rapid serum antibody-detection assay (MiraVista, others)
Cytological or histopathological detection in tissue
- few organisms can cause disease
Ideally do not culture
- is hazardous to laboratory personnel
213
What do Coccidioides look like on cytology?
large (10–80 μm) round, deeply basophilic, double-walled spherule
- may contain 2-5 μm endospores
can be stained with Diff-Quik and Wright stains
214
What are the histopathologic findings associated with coccidiomycosis?
Pyogranulomatous to neutrophilic inflammation in dermis, subcutis
- +/- caseous necrosis, fistulous tracts
Organisms
- Immature spherule = sporangia): 10-20µm diam, no endospores
- Mature spherule: up to 200 µm diam, endospores
- Endospore: 2 5µm diam
--> if you just see released endospores that can be confusing
- Absent budding!
215
Coccidiomycosis
216
Coccidiomycosis
217
What is the treatment and prognosis for coccidiomycosis?
fluconazole or itraconazole
- maybe consider flu due to propensity for CNS disease
- but if bone is involved, consider itra over flu
+/- amphotericin B if severe
surgical debridement (amputation, enucleation, etc) may be needed
treatment generally lasts 6+ mo, some need it lifelong
- continue until IgG titer is 1:2 or lower
- prognosis depends on severity
a Δcps1 vaccine is available for dogs
218
What is the most common species of Sporothrix that are reported to cause illness in veterinary medicine?
Sporothrix schenckii and Sporothrix brasiliensis
- soil and decaying plant matter in tropical/subtropical regions
- hyperendemic in parts of Central and South America
- S. schenckii
219
Which dimorphic fungus is the main species of concern with feline zoonotic transmission?
Sporothrix brasiliensis
220
How do animals tend to contract sporotrichosis infections and what happens following inoculation?
Cutaneous inoculation > inhalation of spores
spores move to regional lymphatics -->
disseminate through blood vessels
- most common with S. brasiliensis
- cats are more susceptible to disease and spread
*can be obtained from cat bites/scratches/contact with lesions
221
What determines the extent of disease with Sporothrix?
Depth of inoculum
Fungal density of inoculum
Host immune system
Fungal virulence factors
222
Which species are most commonly affected with sporotrichosis infections?
Cats >> dogs, horses
223
What are the typical clinical signs associated with sporotrichosis infections?
Firm, subcutaneous masses with purulent discharge
- multiple lesions can be multiple inoculations, self-trauma, grooming
- more common on head, neck, limbs, tail base (fighting?)
- may track along lymphatics in horses
- chronic lesions in horses can resemble proud flesh
- can have mucosal involvement
May have extracutaneous signs (more common in cats)
- cats can develop pulmonary disease in the absence of skin disease
most common form in humans is cutaneolymphatic (50%)
224
How is sporotrichosis diagnosed?
Demonstration in tissue with cytology or histopathology
- more rewarding in cats due to higher numbers
Culture is "gold standard"
- may be negative
- may be contaminated
- is slow-growing (10-15 days)
- is a laboratory hazard
Immunohistochemistry and PCR
- mostly used for species identification
ELISA test detects IgG antibodies in cats
ELISA that detects cell wall antigens in humans and cats
225
What do Sporotrix look like on cytology?
3-5 um diameter, 5-9 um length, cigar shaped, oval to round, budding yeast
have a non-staining wall
seen within the cytoplasm of macrophages, neutrophils, or extracellularly
226
What are the histopathologic findings associated with sporotrichosis?
Diffuse inflammation (dermis, subcutis)
- Pyogranulomatous to neutrophilic
- often very necrotic
Yeasts
- Pleomorphic oval / elongated / cigar shaped
- 1-6µm diameter
- Peripheral clear space
- Extra and intracellular
- Narrow based budding
- Abundant in cats
227
Sporotrix
228
Sporotrix
229
What is the the typical treatment and prognosis of sporotrichosis?
Itraconazole is treatment of choice for feline, canine, and human disease
Other options include keto, flu, K iodide, Na iodide, AMB, terbinafine
- KI and NaI have serious adverse events, especially in cats
No steroids
Cats generally require longer therapy than dogs (can be > 1 year)
Negative prognostic indicators:
- Higher infectious burden
- Involvement of nasal mucosa
- Respiratory signs
Relapse can occur between 3-18 months after stopping therapy
Consider euthanasia due to zoonotic risk
230
Which fungus most commonly affects bearded dragons, green igunana and free living snakes?
Nannizziopsis guarroi
causes yellow to brown crusty lesions of single scales
- may expand to more areas
- "yellow fungus disease"
231
What is Nannizziopsis vriesii (Chrysosporium anamorph of Nannizziopsis vriesii complex aka CANV)?
emerging obligate pathogen of reptiles
- infections in lizards, snakes, and crocodilians
- associated with poor nutrition
has keratinolytic activity
- causes dermatitis and cellulitis in reptiles
likes temps < 37C (grows around 35C, doesn't like mammals)
resistant to cycloheximides
- can grow on DTM
are contagious and often fatal if not properly treated
treatment is usually triazole antimycotics
- Voriconazole use in chameleons is not well tolerated
232
What is Ophidiomyces ophidiicola?
emerging pathogen of captive and wild snakes in North America and Europe
- "snake fungal disease"
keratinophilic fungus
probably transmitted through direct contact
treated with terbinafine
233
What is Emydomyces testavorans?
newly described keratinophilic fungal organism
associated with ulcerative skin and shell disease in chelonians
keratin inclusion cysts are a common feature of infection
234
What is Metarhizium granulomatis (Chameleomyces granulomatis)?
associated with systemic and granulomatous mycosis in chameleons
- include visceral organs, granulomas, glossitis, pharyngitis
treatment with nystatin and/or terbinafine
235
What is Purpureocillium lilacinum?
infects chelonians, crocodilians, bearded dragons, and chameleons
opportunistic pathogen in humans
