Exam 2 - Canine & Feline Fungal Disease

Question 1

why are blasto & histo similar to one another?

Answer 1

both are dimorphic fungi

Question 2

where is blastomyces dermatitidis found in the environment?

Answer 2

sandy, acidic soil near water - especially near deep soil layers

north america - especially eastern river valleys

Question 3

where is histoplasma capsulatum found in the environment?

Answer 3

soil rich in organic nitrogen - bird & bat feces

temperate/sub-tropical regions of the world

Question 4

does blasto primarily affect dogs or cats?

Answer 4

dogs

Question 5

does histo primarily affect dogs or cats?

Answer 5

cats

Question 6

T/F: asymptomatic infections are likely in both blasto & histo

Answer 6

false - rare in blasto & may occur in histo

Question 7

what organism has this regional distribution?

Answer 7

blasto

Question 8

what organism has this region distribution?

Answer 8

histo

Question 9

what is the pathogenesis of blasto?

Answer 9

inhalation of spores - deposition in terminal airways where they turn into yeasts

survival in phagocytes & disseminate to the eyes, bone, & skin

rare wound inoculation

Question 10

what is the pathogenesis of histo?

Answer 10

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

Question 11

T/F: histo may only affect the skin

Answer 11

true

Question 12

what dogs are typically affected by blasto?

Answer 12

sporting, active dogs under 4 years of age

Question 13

what dogs, if any, are affected by histo?

Answer 13

large, sporty ones - weimaraner, pointer, & brittany spaniels

Question 14

what cats are typically affected by histo?

Answer 14

cats, even indoor only, younger than 4 years

Question 15

what are the clinical signs associated with blasto?

Answer 15

severe weight loss, lethargy, exercise intolerance, lameness, coughing/dyspnea, ocular involvement, proliferative or draining skin lesions, & sometimes bone lesions

Question 16

T/F: cats may have GI involvement when infected with blasto

Answer 16

true

Question 17

what are the clinical signs of histo in dogs?

Answer 17

severe large bowel diarrhea, dogs may cough/dyspnea, & hepatomegaly

Question 18

what are the clinical signs of histo typically seen?

Answer 18

lethargy, inappetence, weight loss, PLE, dyspnea, tachypnea, abnormal lung sounds, & enlarged liver/spleen/lymph nodes

Question 19

what may be supportive of blasto in the patient’s history & physical exam?

Answer 19

water exposure

skin lesions, bone pain, & respiratory abnormalities

Question 20

what is your big differential for an older dog with suspicious blasto?

Answer 20

osteosarcoma

Question 21

what may be found on imaging that is supportive of a blasto diagnosis?

Answer 21

diffuse pulmonary disease often with lymphadenopathy

lytic & productive bone lesions & soft tissue swelling

Question 22

what may be found on clin-path that may be supportive of a blasto diagnosis?

Answer 22

hypercalcemia of granulomatous disease, anemia of chronic inflammation, & hyperglobulinemia (polyclonal)

Question 23

what may be seen in the ocular exam in an animal with blasto?

Answer 23

granular changes in the retina

Question 24

what is the cytology/histology of blasto? what can you sample?

Answer 24

broad-based budding yeast with pyogranulomatous inflammation

FNA of lymph nodes, draining tract touch prep, bone biopsy

Question 25

T/F: if you see the organism on cytology when it comes to histo/blasto, it is 100% specific

Answer 25

true

Question 26

what may be supportive of histo in the patient's history & physical exam?

Answer 26

may contain very little outdoor exposure systemic & respiratory signs predominate in cats & gi signs predominate in dogs

Question 27

what may be found on imaging that is supportive of a histo diagnosis?

Answer 27

diffuse pulmonary disease with lymphadenopathy & gi mural thickening seen on endoscopy

Question 28

what may be found on clin-path that may be supportive of a histo diagnosis?

Answer 28

non-specific hypercalcemia of granulomatous disease, anemia of chronic inflammation, polyclonal hyperglobulinemia, & hemophagocytosis in cats

Question 29

what is the cytology/histology of histo? what can you sample?

Answer 29

small intracellular yeast with basophilic center & poorly staining halo & pyogranulomatous inflammation FNA of lymph nodes, rectal scrape, CSF tap

Question 30

what diagnostic test is >92% sensitive in diagnosing blasto & histo?

Answer 30

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

Question 31

T/F: urine EIA is often positive before serum EIA, but you should still consider sending both samples

Answer 31

true

Question 32

why can dilute urine mess with the antigen EIA for blasto & histo?

Answer 32

dilute urine dilutes the antigen in the urine as well & will produce a lower result

Question 33

in the setting of a relapse, _____ EIA is often positive before _____ EIA

Answer 33

urine serum

Question 34

T/F: during treatment of blasto/histo, urine EIA drops even in patients that remain symptomatic

Answer 34

false - it stays positive longer

Question 35

why not culture blasto or histo?

Answer 35

risky for people!!! spores at environmental temps & yeasts at body temps!

Question 36

what is the mechanism of action for antifungals used in treating histo & blasto?

Answer 36

inhibit sterol synthesis - inhibits wall production

Question 37

why is the downside to fungistatic treatment of histo & blasto?

Answer 37

it doesn't directly kill the fungus - long treatment times & very expensive

Question 38

what systemic antifungal has some of the worst side effects?

Answer 38

ketoconazole

Question 39

why use fluconazole if there are CNS signs?

Answer 39

it readily crosses the BBB

Question 40

T/F: itraconazole probably works more rapidly

Answer 40

true

Question 41

what is the mechanism of action of amphotericin b?

Answer 41

punches holes in ergosterol - kills fungal cell directly

Question 42

what are the cons of using amphotericin b?

Answer 42

IV only because poor oral absorption & marked nephrotoxicosis

Question 43

what is the mechanism of action of flucytosine?

Answer 43

pyrimidine antimetabolite that interferes with yeast DNA synthesis

Question 44

what is the mechanism of action of terbinafine?

Answer 44

allylamine ergosterol synthesis inhibitor with high concentrations reaching the skin & subcutaneous tissue

Question 45

what 2 key features predict the prognosis of blasto?

Answer 45

1. severity of pulmonary involvement 2. presence of CNS involvement

Question 46

what percentage of animals relapse after blasto treatment?

Answer 46

20-25%

Question 47

what is the treatment duration of blasto?

Answer 47

treat for one month beyond clinical cure - typically 4 to 6 months

Question 48

which is more treatable, histo or blasto?

Answer 48

histo

Question 49

what is a poor prognostic indicator of histo?

Answer 49

CNS involvement

Question 50

what is the treatment duration of histo?

Answer 50

treat for one month beyond clinical cure - typically 4 to 6 months 2 negative EIAs

Question 51

what are the most common systemic fungal infections seen in companion animals?

Answer 51

blasto & histo

Question 52

what is the first line of defense in treating blasto & histo?

Answer 52

azole therapy

Question 53

what can be a top differential for blasto/histo in systemically ill, wasting patients?

Answer 53

neoplasia