Lecture 4-5 - Fungal dz (Walton) Flashcards
Dimorphic fungi; saprophytic mycelial from in the soil produces infection spores, at body temperature these fungi transform into __ form
yeast
EXAM: types of dimorphic fungi
blastomyces dermatitidis histoplasma capsulatum coccidiodes immitis sporothrix schenckii cryptococcus neoformans
pathologic form of blastomycosis
extra-cellular yeast
thick, refractile, double wall, broad-based budding
endemic to mississippi, missouri, and ohio river valleys and great lakes
blastomycosis
more prominent after heavy rainfall (spore release) in warm weather
found near water in acidic sandy soils
increased __ and __ precede highest incidents of infection for blastomycosis
rainfall, temperature
why don’t all animals contract blastomycosis?
resident soil microbes typically destroy blastomyces in soil
poster child for blastomycosis
labs
how is blastomycosis transmitted
inhalation of spores
contaminated wound
- not considered contagious
predispositions to blastomyces infection
dogs males > females sporting dogs (labs, coonhounds), dobies large breeds 2-4 yo
infection involves inhalation of __ which transforms into a yeast in the __
conidia
lungs (asexual budding)
can be spread systemically (blood or lymph)
inflammatory response often seen with fungal infections
granulomatous to pyogranulomatous
how does blastomycosis avoid the host’s IS (virulence)
BAD1 (impairs complement, can’t phagocytize the yeast)
any systemic dz or fungal dz always do a __ examination
fundic!
anterior uveitis, endophtalmitis, optic neuritis
most common CS of blastomycosis
fever lyphadenopathy harsh lung sounds skin lesions cough, dyspnea, exercise intolerance anorexia, wt. loos
usually localized to lungs and LNs but severe dz can be disseminated systemically
definitive dx for blastomycosis is based on __
cytologic, histopath, or culture
don’t culture! NEVER; can infect lab staff.
easiest and safest way is cytology
ELISA (ag serum assay) is a sensative test for blasto using serum or urine, but it can cross react with __ making positive result not dx for blastomycosis
histoplasma
__ are abnormal in over 85% of cases with blastomycosis and histoplasma
CXR; diffuse miliary pattern of lungs
both can have lytic boney lesions with periosteal reaction
broad-based budding on cytology
blastomycosis
does itraconazole penetrate CNS
No!
tx for blasto
itraconazole
blastomycosis tx; tx for at least __ and continue for at least __ past resolution of CS/rads
2-3mo
1-2mo
the most common systemic fungal dz in cat
cryptococcus neoformans
extra-cellular, thin walled, narrow based budding yeast with thick capsule
cryptococcosis
crytpococcus has a world wide distribution but there are very high incidences of it in
the western US (CA) and E. australia
found in bird excrement, rare in birds due to high BT, inhaled transmission, not contagious, common in cats and purebred dogs
cryptococcus
how does cryptococcus evade the host’s IS
Polysaccaride capsule (prevents phagocytosis)
associated with FeLV/FIV in cats and chronic steroids in dogs
cryptococcus
annimal on IS therapy more likely to get than FIV/FeLV animal
CS of cryptococcus in cat
sneezing, nasal d/c
SC masses
ocular lesions
CS of cryptococcus in dog
CNS signs (dull, blindness, hypermetria, CN defs), ocular lesions (chorioretinitis, retinal detach)
skin lesions less common in dogs
best dx test for cryptococcus
skull rads/CT/MRI ; increased soft tissue in nasal cavity, lysis, deformity, contrast enhancing mass
EXAM: definitive dx for cryptococcus
latex agglutination for Ag in serum, aqueous humor, or CSF
highly sensitive and specific, can quantify
cytology
tx of cryptococcus
fluconazole preferred in cats (will penetrate CNS)
itraconazole is good first choice for cases w/o CNS involvement
very sick patient fluconazole + amphotericin B
can monitor titers to assess tx
small INTRAcellular dimorphic fungus that has a halo and signet ring appearance with double ring, thick wall, and broad based budding
histoplasma capsulatum
subtrop/tropic climate, mississippi, missoouri, ohio river valley, CA, TX
histoplasma capsulatum
similar distribution to blastomycosis
primary reservoir organism for histoplasma
bat and decaying bird guano
not found in fresh feces of birds!
more susceptible to histoplasma
cats, esp persians and cats coinfected with FeLV
histoplasma microconidias are inhaled and transform into yeast which binds to __
CD11-18 integrins on alveolar macs and are phagocytized
replicate in macs, macs are destroyed, causes inflammation in lung
can be spred systemically
subclinical infectious are common and most animals IS will effectively clear this infection
histoplasma
most common CS in dogs with histoplasma
large bowel diarrhea
most common CS in cats with histoplasma
profound wt. loss, fever, respiratory signs, GI dz (can dx off a rectal scrape)
best way to dx histoplasma
cytology! (can be confused with sporothrix ) - lung wash or rectal scrape best
ag assay/ELISA (urine has higher sensitivity than serum). can cross react with blasto.
AGAIN, NO CULTURE; Don’t kill people
2 fungi that have common overlap in radiographic findings and geographic regions
blasto and histo
first choice tx for histoplasma
itraconazole
barrel shaped arthrospores in chains found in the soil, spherules with endospores in tissues
coccidiodes immitis
dry, warm climates, sandy soil, california, NM, arizona areas
coccidiodes immitis
on histopath of coccidiodes immitis what will you see
spherules surrounded by neuts/WBC
respiratory CS occur withing 3wk exposure and disseminated dz develops within __ exposure for coccidiodes
4mo
dog w fever, painful swollen bone lesions, and travel hx to Arizona
coccidiodes
most sensitive test for coccidiodes
ab serology (can’t tell if active infection though, but if see on cytology then know it’s an active infection)
ag titer has very low sensitivity; not recommended
radiographic findings for coccidiodes
hilar lymphadenopathy on CXR
very proliferative bone lesions
tx for coccidiodes
amputation for severe osteomyelitis, enucleation, itraconazole
nasal aspergillosis causative agent? disseminated?
aspergillus fumigatus
aspergillus terreus
these are ubiquitous, opportunistic, saprophytic fungi
GSD are susceptible to aspergillosis bc of __ deficiency
IgA mucosal def
ag test for aspergillosis
aspergillus galactomannan ag (serum or urine)
can have false positive w other mycotic infections (blasto, histo) or plasmalyte IVF
radiographic and AUS findings for aspergillus
diskospondylitis
osteomyelitis
thoracic lymphadenomegaly
pelvic dilation in kidneys (AUS)
definitive dx for aspergillosis
culture and/or PCR
another fungus with similar CS to cryptococcus that occurs in cat nose
sporothrix schenckii
fungus that looks similar to histoplasmosis on cytology
sporothrix
potentially zoonotic fungus
sporothrix!
water molds that causes granulomatous and eosinophilic inflammation
pythium insidiosum and lagenidiosis sp.
large, infrequently septate hyphae with non parallel wall
pythium, lagenidiosis
how are oomycetes (water molds) different from fungi
cell wall lacks chitin and ergosterol (this is the target for most antifungal drugs!)
diploid
non-septate hyphae
eosinophilic pyogranulomatous inflammation
water molds! pythium and lagenidiosis
when ID a water mold it is important to do __ to determine prognosis and tx
PCR
Tx for water molds
aggressive sx excision
antifungals
insect killer fungi that are best dx on culture and tx with aggressive sx excision
basidiobolus and connidiobolus
patients on __ are predisposed to infections with these opportunistic fungi (phaeohyphomycosis, hyalohyphomycosis)
cyclosporine
__ is caused by pigmented fungi and __ is caused by nonpigmented fungi
phaeohyphomycosis (confined to skin and SC)
hyalohyphomycosis (local and systemic dz)
dark-walled, irregularly septate hyphae or yeast-like cells containing melanin
phaeohyphomycosis
non-pigmented, frequenly septate, branching hyphae that can cause disseminated dz
hyalohyphomycosis
