Case 2 Answer


  1. (d) Yeasts are oval to round, 2-4mm, surrounded by a clear halo and stain positive with the fungal special stain GMS.
  2. (a) Culture is not recommended because of pathogenic potential, but is diagnostic; (b)Serological tests for antibodies directed against Histoplasma antigens are often falsely negative; (c) histopathology and GMS special staining allows fungi identification and fair presumptive diagnosis. IHC has been also published; (d) specific PCR can provide a definitive diagnosis, but is not commonly used.


  1. Histoplasmosis is the second most commonly reported systemic fungal disease in cats.
  2. Most infected cats have disseminated disease and only rarely are signs restricted to the gastrointestinal tract. Affected animals exhibit a wide range of non-specific clinical signs, including: mental depression, fever, intractable chronic diarrhoea with anorexia and weight loss, anaemia and pale mucous membranes. Dyspnoea, tachypnoea, and abnormal lung sounds are also frequent in the pulmonary form of the disease. Other frequent findings include peripheral or visceral lymphadenomegaly, splenomegaly, and hepatomegaly and icterus. Ulcerative and nodular lesions may also be found in the skin and oral cavity.
  3. Organs affected in histoplasmosis will depend on whether the disease is pulmonary or disseminated. Lesions restricted to the GI tract, mainly the colon, are less frequent, but are also possible, suggesting ingestion as a possible route of infection in such cases.
  4. Histoplasma capsulatum is endemic throughout temperate and subtropical regions of the world with warm, moist and humid conditions, and is especially prevalent in the Americas, India, and southeastern Asia.
  5. As with other systemic mycoses, direct transmission of histoplasmosis from animal to animal or animal to humans has not been reported.

Grooters AM, Foil CS. Miscellaneous fungal diseases. In: Greene CE, ed. Infectious Diseases of the Dog and Cat. 4th ed. St. Louis, MO: Saunders Elsevier; 2012:614.