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33 Cards in this Set
- Front
- Back
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What is the causative agent of histoplasmosis?
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Dimorphic fungus Histoplasma capsulatum
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What is the most important thing to remember about fungal infections?
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Distribution & geographic location**
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Where is histoplasma capsulatum located in the environment?
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Soil borne organism that prefers rich, moist environments
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What is the geographic distribution of histoplasmosis?
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Throughout much of the western hemisphere and in 31 states of the US
-**disease occurs primarily in the Ohio, Missouri and Mississippi River valleys |
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What form does Histoplasma capsulatum exist as in the environment? What does this form produce?
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Mycelial form that produces infective macroconidae and microconidia
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How do mammals contract histoplasmosis?
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Infection through inhalation of the microconidia or, less likely, via the GI tract following ingestion
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What happens to the Histoplasma capsulatum after being inhaled into the lungs of a mammal?
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The microconidia convert to the yeast form and reproduce by budding
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How do histoplasma disseminate to the blood stream and lymphatics?
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In the lungs organisms are phagocytized by the mononuclear phagocyte system (MPS) where intracellular replication takes place- intracellular location allows dissemination
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What is the signalment of dogs that are predisposed to histoplasmosis?
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Young (<4 years)
No apparent sex predisposition Pointers, weimaraners, brittany spaniels (behavioral) |
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What cats are most susceptible to histoplasmosis?
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Young (<4 years)
Females -cats as susceptible as dogs |
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What are the 8 organ systems commonly affected by histoplasmosis in dogs?
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1) Lungs
2) GI tract 3) Lymph nodes 4) Liver 5) Spleen 6) Bone marrow 7) eyes 8) Adrenal glands |
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True or false. Histoplasmosis is not a zoonotic disease.
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False, its zoonotic
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What 5 organ systems are commonly affected in cats with histoplasmosis?
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1) Lungs**
2) Liver (one of biggest livers you will see) 3) Lymph nodes 4) Eyes 5) Bone marrow |
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Are most histoplasmosis cases clinical or subclinical?
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Subclinical
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What clinical signs of histoplasmosis are COMMONLY seen in cats?
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-often nonspecific (depression, weight loss, fever, anorexia, pale mm)
-Dyspnea, tachypnea, abnormal lung sounds |
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What clinical signs of histoplasmosis are sign 1/3 of the time in cats? (3)
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Lymphadenopathy
Splenomegaly Hepatomegaly |
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What are the less commonly affected organs with histoplasmosis in cats? (3)
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Eyes, bones and skin may be affected
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What are the 3 nonspecific signs of histoplasmosis in dogs?
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1) Inappetence
2) Fever 3) Weight loss |
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What clinical signs are usually seen in dogs?
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Usually disseminated w/ GI disease:
-Tenesmus -Hematachezia -voluminous diarrhea -hyporporteinemia w/ small bowel disease |
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Are the lungs affected in DOGS with histoplasmosis?
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Yes, isolated lung involvement may occur ---> coughing, dyspnea, abnormal lung sounds
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What are the less common clinical signs of histoplasmosis in dogs? (5)
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Hepatomegaly
Splenomegaly Visceral lymphadenopathy Icterus Ascites |
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What do you find on chemistry and hematology of an animal w/ histoplasmosis?
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Non-specific
-pancytopenia in cats w/ bone marrow involvement -occasionally, organisms may be seen w/in macs |
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**What can be seen on thoracic radiographs that are HIGHLY suggestive of fungal pneumonia?
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Nodular pattern or hilar lymphadenopathy
-often not present -hilar lymphadenopathy= common in dogs |
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What type of lung pattern does histoplasmosis cause?
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Linear or diffuse interstitial pattern that may coalesce to a nodular interstitial pattern
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What are 4 methods used to diagnose histoplasmosis?
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1) Demonstration of the organism by cytology
2) Demonstration of the organism by histopathology -endoscopic biopsies 3) Fungal culture -not recommended in practice bc potential for infection 4) Skin testing & serology unreliable |
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Where are histoplasma organisms found upon cytology?
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Within macrophages
-characteristic basophilic center surrounded by a clear halo due to shrinkage of the capsule during fixation |
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What samples do you want to perform cytology on when trying to diagnose histoplasmosis? (2)
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Airway washing
Rectal scrapings |
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What sample can you use for serology when trying to diagnose histoplasmosis?
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Urine + serum antigen
-quantitative |
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True or false. It takes a long time to treat fungal disease with antifungals.
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True, takes ~6 months
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What is the drug of choice for treating histoplasmosis? Why?
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Itraconazole - but more expensive than fluconazole, but has better penetration of the eye and CNS (commonly places affected by fungal dz)
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Why is amphotericin B the last treatment option for histoplasmosis?
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Has to be given IV (@hospital) and high rate if there's kidney disease
-reserve for animals that don't respond to itraconazole or fluconazole |
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How long should therapy for histoplasmosis continue?
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At least 4-6 months, continue a month past resolution of clinical signs
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What is the prognosis of histoplasmosis?
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Fair to good, depends on the extent of infection
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