Exam 2 - Canine & Feline Fungal Disease Flashcards
why are blasto & histo similar to one another?
both are dimorphic fungi
where is blastomyces dermatitidis found in the environment?
sandy, acidic soil near water - especially near deep soil layers
north america - especially eastern river valleys
where is histoplasma capsulatum found in the environment?
soil rich in organic nitrogen - bird & bat feces
temperate/sub-tropical regions of the world
does blasto primarily affect dogs or cats?
dogs
does histo primarily affect dogs or cats?
cats
T/F: asymptomatic infections are likely in both blasto & histo
false - rare in blasto & may occur in histo
what organism has this regional distribution?
blasto
what organism has this region distribution?
histo
what is the pathogenesis of blasto?
inhalation of spores - deposition in terminal airways where they turn into yeasts
survival in phagocytes & disseminate to the eyes, bone, & skin
rare wound inoculation
what is the pathogenesis of histo?
inhalation of spores - deposition in terminal airways where they turn into yeasts
survival in macrophages & disseminate to the gi tract, eyes, skin, & bone
rare wound inoculation
T/F: histo may only affect the skin
true
what dogs are typically affected by blasto?
sporting, active dogs under 4 years of age
what dogs, if any, are affected by histo?
large, sporty ones - weimaraner, pointer, & brittany spaniels
what cats are typically affected by histo?
cats, even indoor only, younger than 4 years
what are the clinical signs associated with blasto?
severe weight loss, lethargy, exercise intolerance, lameness, coughing/dyspnea, ocular involvement, proliferative or draining skin lesions, & sometimes bone lesions
T/F: cats may have GI involvement when infected with blasto
true
what are the clinical signs of histo in dogs?
severe large bowel diarrhea, dogs may cough/dyspnea, & hepatomegaly
what are the clinical signs of histo typically seen?
lethargy, inappetence, weight loss, PLE, dyspnea, tachypnea, abnormal lung sounds, & enlarged liver/spleen/lymph nodes
what may be supportive of blasto in the patient’s history & physical exam?
water exposure
skin lesions, bone pain, & respiratory abnormalities
what is your big differential for an older dog with suspicious blasto?
osteosarcoma
what may be found on imaging that is supportive of a blasto diagnosis?
diffuse pulmonary disease often with lymphadenopathy
lytic & productive bone lesions & soft tissue swelling
what may be found on clin-path that may be supportive of a blasto diagnosis?
hypercalcemia of granulomatous disease, anemia of chronic inflammation, & hyperglobulinemia (polyclonal)
what may be seen in the ocular exam in an animal with blasto?
granular changes in the retina
what is the cytology/histology of blasto? what can you sample?
broad-based budding yeast with pyogranulomatous inflammation
FNA of lymph nodes, draining tract touch prep, bone biopsy
T/F: if you see the organism on cytology when it comes to histo/blasto, it is 100% specific
true
what may be supportive of histo in the patient’s history & physical exam?
may contain very little outdoor exposure
systemic & respiratory signs predominate in cats & gi signs predominate in dogs
what may be found on imaging that is supportive of a histo diagnosis?
diffuse pulmonary disease with lymphadenopathy & gi mural thickening seen on endoscopy
what may be found on clin-path that may be supportive of a histo diagnosis?
non-specific
hypercalcemia of granulomatous disease, anemia of chronic inflammation, polyclonal hyperglobulinemia, & hemophagocytosis in cats
what is the cytology/histology of histo? what can you sample?
small intracellular yeast with basophilic center & poorly staining halo & pyogranulomatous inflammation
FNA of lymph nodes, rectal scrape, CSF tap
what diagnostic test is >92% sensitive in diagnosing blasto & histo?
urine antigen EIA - enzyme immunoassay that amplifies detection
detects the antigen from the galactomannan in the cell wall excreted in the urine & it will end up in the urine regardless of the site of active infection
T/F: urine EIA is often positive before serum EIA, but you should still consider sending both samples
true
why can dilute urine mess with the antigen EIA for blasto & histo?
dilute urine dilutes the antigen in the urine as well & will produce a lower result
in the setting of a relapse, _____ EIA is often positive before _____ EIA
urine
serum
T/F: during treatment of blasto/histo, urine EIA drops even in patients that remain symptomatic
false - it stays positive longer
why not culture blasto or histo?
risky for people!!! spores at environmental temps & yeasts at body temps!
what is the mechanism of action for antifungals used in treating histo & blasto?
inhibit sterol synthesis - inhibits wall production
why is the downside to fungistatic treatment of histo & blasto?
it doesn’t directly kill the fungus - long treatment times & very expensive
what systemic antifungal has some of the worst side effects?
ketoconazole
why use fluconazole if there are CNS signs?
it readily crosses the BBB
T/F: itraconazole probably works more rapidly
true
what is the mechanism of action of amphotericin b?
punches holes in ergosterol - kills fungal cell directly
what are the cons of using amphotericin b?
IV only because poor oral absorption & marked nephrotoxicosis
what is the mechanism of action of flucytosine?
pyrimidine antimetabolite that interferes with yeast DNA synthesis
what is the mechanism of action of terbinafine?
allylamine ergosterol synthesis inhibitor with high concentrations reaching the skin & subcutaneous tissue
what 2 key features predict the prognosis of blasto?
- severity of pulmonary involvement
- presence of CNS involvement
what percentage of animals relapse after blasto treatment?
20-25%
what is the treatment duration of blasto?
treat for one month beyond clinical cure - typically 4 to 6 months
which is more treatable, histo or blasto?
histo
what is a poor prognostic indicator of histo?
CNS involvement
what is the treatment duration of histo?
treat for one month beyond clinical cure - typically 4 to 6 months
2 negative EIAs
what are the most common systemic fungal infections seen in companion animals?
blasto & histo
what is the first line of defense in treating blasto & histo?
azole therapy
what can be a top differential for blasto/histo in systemically ill, wasting patients?
neoplasia
