Histoplasmosis Flashcards
Histoplasmosis capsulatum
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
Epidemiology
Similar to blasto --Big difference = size. Blasto = BIG. Histo = small Mycelial stage --free living in soil produces spores Microconidia = source of IFX to animals
Mode of IFX
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!!!
Clinical Findings
Young <4yr
Working breeds?
Systemic signs common: inapp, WL, fever unresponsive to ABX
Resp signs: dyspnea, cough, harsh lung sounds
–Can be only signs!!!
Other CS
GI signs = very common --usually large bowel diarrhea --Severe wgt loss Liver, increased LN, increased spleen - infrequent Ocular skins, CNS - rare
Lab Findings: CBC
Normocytic, normochromic non-reg anemia (chronic disease)
Leukocytosis variabke
Stress leukogram usual
Organisms in cells - rare - bunch of grapes crowding out a macrophage
Lab findings: chemistry
Unremarkable in dogs w/ resp dz only
Marked hypoalbuminemia (PLE, blood loss)
Later in disease - also see increased globulins
Increased liver enzymes
How clinically distinguish blasto from histo?
Histo produces enlargement of bronchial LN. Blasto does not
Cytology
Organisms numerous in affected tissues - aspirate cytology
Lung aspirate, rectal scrapings, skin scrapes
BM may contain organisms when other sites fail
RBC phagocytosis
Dx Isolation
Mycelia phrase 7-10d at room temp
Microconidia in culture very infectious
Dx immunodiagnosis
Intradermal skin test unreliable in dogs
Serology also unreliable - often false negatives
Therapy
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
Therapy drug choices - itraconazole
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
Therapy drug choices - fluconazole
Many use as first choice because cost has come way down
–Penetrates CNS and ocular tissues well
Use in patients refractory to AMB, itraconazole
Prognosis
Pulmonary form: fair to excellent
Dissemination: fair to good
GI dz: fair
Ocular or CNS involvement: poor