Derm 7 - more fungal Flashcards
often overlooked pathogen for chronic pododermatitis cases, and other referrals
Malassezia dermatitis
nail biting dogs should be checked for what condition? what might we see?
Therapy?
vs other similar conditions?
Malassezia paronychia
- may present with nothing more than discoloured claws
- A closer look at the base of the claws may reveal a brown discolouration with a waxy exudate/film
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These patients often respond well to antifungal therapy, though many respond better to systemic therapy than topical treatment, likely a result of the difficulty in treating this area effectively
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Bacterial and fungal claw disease can also lead to nail biting of course, but these are usually associated with a more significant inflammatory reaction.
malessezia - how many species, host preferences?
- which is most common? where does it live?
There are now 14 species identified, with different preferences for host species.
- Malassezia pachydermatis is most commonly isolated
> a commensal isolated from skin of healthy dogs, primarily from seborrheic areas and skin fold regions (chin, interdigital, axilla, groin, ear canals, lip, buccal mucosa, anal sacs, anal mucosa, vagina)
> Less frequently isolated from cats
malessezia growth enhanced when what other organism present?
Growth of Malassezia enhanced when skin co-colonized with Staphylococcus pseudintermedius
malessezia dermatitis clinical signs
Pruritus
Erythema, scale (honey-coloured to brown), greasy, crust
Occasionally papular dermatitis
Lichenification and hyperpigmentation with chronicity
Often rancid odour
Locations:
malessezia common sites on dogs
Paws most common (interdigital, palmoplantar)
Paronychia (claw fold inflammation)
Ear canals
Ventral neck
Axillary
Lips
Inguinal/medial thigh regions
Perianal/perivulvar
malessezia common sites on cats
paronychia
otitis
chin acne
facial dermatitis
adherent brownish scale, ventral distribution
Malassezia is commonly isolated from claws of Devon Rex cats
malessezia diagnosis methods
Cytology
Culture – Many normal dogs will have some Malassezia on fungal culture
Histopathology – insensitive - Malassezia lost in part with normal processing (as part of Stratum corneum is lost)
Clinical and Historical Suspicion
Response to antifungal treatment
malessezia treatment, which are best? what do we need to do to ensure success?
- Systemics (more effective)
> Baseline liver enzymes and periodic monitoring with all azoles
> Underlying disease must be addressed to prevent or reduce recurrences. Client education crucial.
- Ketoconazole
> numerous drug interactions
- Fluconazole
- Itraconazole (cats)
- Terbinafine
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- In milder cases where owner able to be diligent
- Miconazole shampoo, ketoconazole, etc.
- Acidifying ear canal beneficial
Sporotrichosis
- organism
- type of disease, pathogenesis
- who is at risk?
- Sporothrix schenckii
Subcutaneous mycosis
Wound contamination- yeast phase establishes infection - people and animals at risk > zoonosis, generally from felines to humans
Sporotrichosis in dogs - clinical signs, forms of disease
- Uncommon to rare
- from puncture wounds, thorns, splinters
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Cutaneous form (most common)
o multiple firm nodules (may ulcerate, draining tracts) o ulcerated plaques with raised borders
o head, pinnae, trunk
o not painful or pruritic, healthy otherwise
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Cutaneolymphatic form
o nodule on distal aspect of limb
o ascending infection through lymphatics
o secondary nodules may be firm or fluctuant
o regional lymphadenopathy
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Disseminated (extremely rare): usually related to immunosuppressive medications
Sporotrichosis
- clinical signs in cats
- Uncommon
- Inoculation by claws or teeth of another cat
- Head, distal limbs, tail base, mucosal involvement
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May initially present with fight wound abscess, draining tracts, cellulitis
Purulent exudate, crusted nodules, large areas of necrosis
Suspect in cats with non-healing bite wound abscess
Cats may have disseminated form- even though systemic involvement may not be obvious
Lymph nodes may fistulate, +/- lethargy, depression, anorexia, fever
Large numbers of organisms in draining fluids (unlike other species)
Cryptococcus neoformans
- type of organism
- where it is found
- species most susceptible
- site of infection, symptoms
- zoonotic?
Dimorphic, saprophytic, encapsulated yeast-like fungus
Found in pigeon excrement, nitrogen-rich environments
Global, but most often in humid, subtropical: Australia, Western US and Canada
Cats most susceptible, including indoor
Nasal cavity usually primary site of infection
Converts to yeast form in tissues
In cats, direct spread from nasal cavity across cribriform plate –> meningitis and may track along optic nerve–> eye
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Not zoonotic - as organism doesn’t aerosol from sites of infection
Cryptococcus neoformans clinical signs, in dogs and cats
Dogs: very rare, CNS disease more common, 20% have cutaneous lesions
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Cats:
most common deep mycosis of the cat
upper respiratory (nasal cavity), cutaneous, lymph nodes, CNS (meninges), ocular, (peripheral blindness and
dilated pupils- marker for CNS involvement)
intranasal granulomatous disease most common; cutaneous signs often a sequel to nasal infection (local
extension)
less common lower respiratory signs, occasionally otitis media
systemic signs with visceral or nasal disease- fever, anorexia, weight loss
70% of cases with upper respiratory signs, polyp-like mass visible in nostril or firm, mushy SQ swelling over
bridge of nose
association with FeLV, and FIV in cats is controversial; no longer appears to be a risk factor; may affect
prognosis
cryptococcus neoformans diagnosis
Cytology
Histopathology
Serology
Culture
Blastomycosis dermatitidis
- how common
- type of organism
- form, where found
Most common systemic mycosis in small animal practice
Dimorphic, saprophytic fungus
Grows in a saprophytic mycelial form, which produces infective spores
Ecologic niche includes moisture, soil type (sandy, acid), presence of wildlife, soil disruption
Even in endemic areas, not widely distributed
Endemic areas: Mississippi, Missouri, Ohio river valleys, Great Lakes region, Southeastern Canada
Most people and animals in endemic areas show no serologic evidence of exposure and disease uncommon
blastomycosis risk factors
o Proximity to a body of water
o Dirt-moving activities (excavation)
o Likely “point of source exposure”- seem to have multiple cases within brief period
blastomycosis pathogenesis
Inhalation of spores from environment–> enter terminal airway –> primary infection in lungs–> disseminates
Organism transforms into yeast form at body temperature
Yeast from body/coughing animal too big to enter terminal airway-thus transmission unlikely
Skin lesions usually from disseminated disease. Rare cases of focal lesion from a puncture.
blastomycosis clinical signs in dogs and cats
- dogs
Young male large sporting breeds most common
Most common affected organs after dissemination from lungs: skin, subcutaneous tissue, eyes, bones, lymph
nodes, external nares, brain testes
Exercise intolerance, coughing, dyspnea, anorexia, weight loss
Uveitis (40% ocular signs), lameness (30% bone lesions)
Skin lesions (20-50%)
usually multiple lesions: papules, nodules, plaques, ulcers, draining tracts, subcutaneous abscesses - nasal
planum, face and claw beds preferred sites
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Cats: very rare - Dyspnea, draining skin lesions (especially digits), weight loss
blastomycosis diagnosis
Cytology: gold standard
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Biopsy:
Culture: not recommended for in hospital - danger of infection from mycelial form (advise commercial
laboratory of suspicion)
Urine Antigen test
Serologic testing:
ELISA, agar-gel immunodiffusion antibody tests- low sensitivity, high specificity- no longer recommended -
antibodies persists once cured
RIA better sensitivity- not readily available
Histoplasmosis
- organism
- clinical findings in dogs and cats
Histoplasma capsulatum
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Uncommon disease
Young dogs- Pointers, Weimaraners, Brittany spaniels
Seen in cats just as frequently - 2nd most common systemic mycosis in cats
Dogs often local granulomatous disease in lungs
Most cats disseminated disease
Anorexia, weight loss, fever, coughing, dyspnea, gastrointestinal (especially dogs) , ocular, skin disease,
anemia
Bone and skin involvement uncommon
Skin lesions: usually multiple papules, nodules, ulcers, draining tracts
Coccidiomycosis
- organism
- clinical signs, lesions
Coccidiodes immitis -
“San Joaquin Valley Fever”
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Commonly affected organs: bone, eyes, heart, testicles, CNS, visceral organs
Young male dogs, Dobermans and Boxers predisposed to disseminated infection
Coughing, dyspnea, fluctuating fever, anorexia, weight loss, lameness, skin disease, ocular disease, CNS
(seizures), constricting pericarditis
Bone lesions may become apparent years after initial exposure- initial respiratory signs may not have been apparent
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Skin lesions:
Uncommon
almost always over sites of infected bone
multiple papules, nodules, abscesses, draining tracts, ulcers
cats: rare, but skin lesions most predominant sign, without bone involvement
