Histoplasmosis Flashcards

1
Q

Histoplasmosis capsulatum

A

DIMORPHIC FUNGUS
Temperate/subtropical environments
Grows best in nitrogen-rich organic material such as bird or bat excrement
Isolated from 31 states –> mainly around major river valleys

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2
Q

Epidemiology

A
Similar to blasto 
--Big difference = size. Blasto = BIG. Histo = small 
Mycelial stage 
--free living in soil produces spores 
Microconidia = source of IFX to animals
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3
Q

Mode of IFX

A

Inhale microconidia –> terminal bronchioles –> convert to yeast stage at 37C (divide by budding) –> phagocytosed by mononuclear cells (divide) –> dissemination (blood, lymph)

  • -Some IFX confined to resp system
  • -Most P: cell-mediated immunity controls IFX
  • -GI dz can occur w/o resp IFX –> CAN BE INGESTED TO CAUSE INFECTION!!!
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4
Q

Clinical Findings

A

Young <4yr
Working breeds?
Systemic signs common: inapp, WL, fever unresponsive to ABX
Resp signs: dyspnea, cough, harsh lung sounds
–Can be only signs!!!

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5
Q

Other CS

A
GI signs = very common
--usually large bowel diarrhea 
--Severe wgt loss 
Liver, increased LN, increased spleen - infrequent 
Ocular skins, CNS - rare
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6
Q

Lab Findings: CBC

A

Normocytic, normochromic non-reg anemia (chronic disease)
Leukocytosis variabke
Stress leukogram usual
Organisms in cells - rare - bunch of grapes crowding out a macrophage

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7
Q

Lab findings: chemistry

A

Unremarkable in dogs w/ resp dz only
Marked hypoalbuminemia (PLE, blood loss)
Later in disease - also see increased globulins
Increased liver enzymes

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8
Q

How clinically distinguish blasto from histo?

A

Histo produces enlargement of bronchial LN. Blasto does not

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9
Q

Cytology

A

Organisms numerous in affected tissues - aspirate cytology
Lung aspirate, rectal scrapings, skin scrapes
BM may contain organisms when other sites fail
RBC phagocytosis

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10
Q

Dx Isolation

A

Mycelia phrase 7-10d at room temp

Microconidia in culture very infectious

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11
Q

Dx immunodiagnosis

A

Intradermal skin test unreliable in dogs

Serology also unreliable - often false negatives

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12
Q

Therapy

A

Pulmon form may be self limiting - no Tx?
Chemotherapy recommended as dissemination occurs early in infection
Dogs w/ hilar lymphadenopathy - tx with steroids for a few days
Most req 4-6mo of itraconazole

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13
Q

Therapy drug choices - itraconazole

A

Drug of choice but that may be changing

  • -does not penetrate ocular or CNS well
  • -Cats seem to improve in spite of this
  • -Severe dz: combo of AMB induction followed by itraconazole
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14
Q

Therapy drug choices - fluconazole

A

Many use as first choice because cost has come way down
–Penetrates CNS and ocular tissues well
Use in patients refractory to AMB, itraconazole

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15
Q

Prognosis

A

Pulmonary form: fair to excellent
Dissemination: fair to good
GI dz: fair
Ocular or CNS involvement: poor

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16
Q

Public Health

A

Transmission from animal –> animal not reported
–has been reported for blasto
Lab cultures infectious to man