Clinical Signs of Histoplasmosis

Clinical signs of histoplasmosis can be vague and insidious and overlap with other inflammatory diseases including bacterial infection, cancer, and immune mediated disease.

  • Anorexia
  • Weight loss
  • Lethargy
  • Fever, unresponsive to antibiotics
  • Tachypnea/dyspnea
  • Lymphadenopathy
  • Cough (dog)
  • Diarrhea (dog)
  • Lameness or joint swelling (cat)
  • Blindness

Treatment And Testing

For the best chance of a positive clinical outcome, early diagnosis and appropriate treatment are key. Testing urine for antigen with the MVista® Histoplasma Antigen Quantitative EIA is the single most accurate diagnostic test. With the wide array of clinical
scenarios, other non-invasive tests might be required and a list of available tests for histoplasmosis is found below.

What is Histoplasmosis?

Histoplasmosis is caused by the dimorphic fungus, Histoplasma. This fungus is commonly found in soil with high nitrogen content (contaminated with bird or bat droppings).

Both pets and humans can develop histoplasmosis upon inhaling the fungal spores aerosolized in contaminated dirt or dust. Once in the lungs, the mold transforms into a yeast. There an appropriate immune response can eliminate the fungus, or it can cause disease localized to the lungs or disseminate through the blood or lymphatics causing disease in many other organ systems. As a result of dissemination, chronic disease can be localized to essentially any organ.

Both cats and dogs are at risk, and even cats that never leave the house develop histoplasmosis, accounting for approximately 1/3 of the reported cases.

Estimated Areas with Histoplasmosis in the United States

Learn more about Histoplasmosis

While many animals, with an appropriate immune response, exposed to Histoplasma likely never develop clinical signs, life-threatening dissemination to many organs is the most common form seen in animals that do show signs. This is likely due to an overwhelming inoculum or less commonly immunocompromise.