Blastomycosis

Question 1

Blastomyces dermatitidis

Answer 1

Dimorphic fungus causing systemic mycoses
–At room temp - mycelia phase (culture)
–at body temp - budding yeast phase (tissues)
Yeast stage = refractile, double-contoured cell wall
Infects people, dogs
–Rarely horses, sea lions, ferrets, polar bears, cats

Question 2

Epidemiology

Answer 2

Reservoir
–Soil
–Not widely distributed
Few people in endemic areas are sero positive
Point source of exposure within endemic area
Once exposed, infection usually follows

Question 3

Mode of IFX

Answer 3

Inhal of spores from mycelial stage
–Spores enter airways –> terminal bronchioles
Yeast stage too large to enter airways
Skin inoculation rare but can occur
Cutaneous lesions should be considered sign of dissemination

Question 4

Transmission EXAM

Answer 4

Do you have to inhale the spores to be infected? No! Skin inoculation if trauma, open wound, or infection

Question 5

Mode of dissemination

Answer 5

From primary site in lungs, all other tissues
–esp eyes, skin, bones, LN, nares, brain, testes
–Rarely mouth, nasal passages, prostate, liver, heart ‘
Lung lesions can be resolved by the time dissemination occurs
–Rads may look normal, see more on HP
Dissemination via blood, lymph

Question 6

Host response

Answer 6

Dogs more susceptible than people/cats 
Male dogs more susceptible than females 
--But females survive therapy better than males 
Large breed dogs more exposed 
Age: most 1-5yrs of age 
No seasonal incidence

Question 7

Clinical findings: disseminated dz

Answer 7

A, WL, resp signs
Ocular dz, uveitis, retinal detachment
Lameness
Skin lesions, draining tracts

Question 8

DX CBC

Answer 8

Mild normocytic, normochromic anemia
Leukocytosis w/ left shift
Lymphopenia

Question 9

DX Biochemistry

Answer 9

Increased globulins, decreased albumin

Increased calcium without bone lesions (very rare)

Question 10

Dx

Answer 10

Culture: NOT IN THE HOSPITAL
Serology: not definitive alone but with hx, CS, RADS - Dx
1) AGID
–good sen/spec
–Pos early dz
–Ab persist, not useful for following treatment
2) ELISA
–Get cross reactivity with other organisms unless antigens are pure

Question 11

Dx Urine Antigen Test

Answer 11

Replaced by serum/Ab testing
About 95% of known positive dogs test positive
Does cross react with Histoplasma
Useful for monitoring treatment along with chest RADS
–following/tracking the antigen very important part of treatment

Question 12

DX PCR

Answer 12

Only useful to confirm identity of organism on cytology

Does not surpass urine antigen testing

Question 13

Amphotericin B

Answer 13

Effective, rapid acting but nephrotox and phlebitis
Slow IV infusion w/ mannitol, use of lipid complexes, or SQ infusion to decrease nephrotox
Can get fever after first infusion
Does not cross BBB
Monitor BUN - more sensitive to monitor urine for appearance of casts –usually hyaline

Question 14

Therapy: itraconazole

Answer 14

Alters ergosertol of fungal cell wall
Slower acting than AMB but as effective 
--PO
--Fewer SE (watch ALT)
--More \$\$$
Not excreted in the urine so no use against fungal UTIs

Question 15

Prognosis

Answer 15

2 prognostic indicators
1- brain involvement –> usually fatal (steroids)
2 - severe lung involvement –> worsens w/ tx
Mild ocular dz - can be cured
–If glaucoma or enophthalmitis, prog poor
Re-IFX does not seem to occur

Question 16

Public Health Considerations

Answer 16

No danger of aerosol transmission
Penetrating would can cause local IFX
Send cultures to a lab!!!