Canine and feline histoplasmosis: A review of a widespread fungus - Veterinary Medicine
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Canine and feline histoplasmosis: A review of a widespread fungus
Infection with this pathogenic fungus most commonly results from inhaling spores from contaminated soil. The infection should be treated promptly to avoid dissemination, which carries a poorer prognosis.



The results of routine diagnostic tests such as a complete blood count, a serum chemistry profile, a urinalysis, and radiographic or ultrasonographic examinations may raise your suspicion of histoplasmosis.

Complete blood count

The most common hematologic abnormality in dogs and cats with disseminated histoplasmosis is a normocytic, normochromic nonregenerative anemia.10,11,46 Anemia in dogs is usually mild to moderate; the packed cell volume (PCV) ranges from 20% to 37% (reference range = 35% to 57%47).8 In a report of 12 cats, anemia ranged from moderate (PCV = 20% to 25%) to severe (PCV < 20%) (reference range = 30% to 45%47).15 Causes of anemia may include intestinal blood loss, chronic inflammation, or bone marrow infiltration.8,11,30

Other hematologic abnormalities reported in dogs include monocytosis, neutrophilia, eosinopenia, and, less commonly, neutropenia, eosinophilia, basophilia, or a degenerative left shift.8-11,35,48,49 While infrequently observed, histoplasmosis is reported as a risk factor for neutropenia.48 Mild to severe thrombocytopenia may occur in as many as half of affected dogs.11 In a report of three dogs with histoplasmosis, platelet counts ranged from 5,000 to 81,000/mm3 (reference range = 211,000 to 621,000/mm3). Thrombocytopenia may be caused by increased platelet consumption or, possibly, sequestration in association with splenomegaly and hepatomegaly.46

A wide range of other hematologic abnormalities also occur in cats. Both neutropenia and neutrophilia have been reported,1,18,38,50 and pancytopenia was documented in one cat with toxic changes to the neutrophils.18 Thrombocytopenia may be observed in as many as one-third of affected cats.11 Chronically infected cats may not show any hematologic abnormalities.38

Serum chemistry profile

Hypoalbuminemia was reported in five of five cats and nine of 11 dogs with disseminated histoplasmosis.8,15 The hypoalbuminemia may result from intestinal blood loss, decreased synthesis associated with inflammation, liver dysfunction, or protein-losing enteropathy.8-11,15 Hyperglobulinemia secondary to inflammation is reported in dogs and cats.8,10,15,33,38 Hepatic involvement can result in increased serum alanine aminotransferase (ALT) activity, alkaline phosphatase activity, and total bilirubin concentration.8,9,11,38 Hypercalcemia has been reported in cats with histoplasmosis.38


While proteinuria has been reported,8,38 urinalysis results in dogs and cats with histoplasmosis are usually within reference ranges.10,50


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