Histoplasmosis is a chronic, non-contagious fungal infection caused by the soil-dwelling fungus Histoplasma capsulatum. The fungus may infect both humans and animals. It thrives in warm, moist environments, commonly found in soil that contains bird or bat feces.
Humans and animals commonly get this infection by inhaling fungal spores, which then reach the lower airways where they multiply. The organism may also enter the body through the mouth and set up an infection in the intestines. The fungal infection has the potential to spread to other parts of the body through the bloodstream or lymphatic system. With a generalized infection, the fungus can become established in the lymph nodes, spleen, liver, bone marrow, skin, or eyes.
The signs of histoplasmosis are usually not specific for this disease. In pets, symptoms include mild fever and depression, which are signs associated with many other ailments of cats. If the lungs are the primary site of infection, the cat may show signs of respiratory distress such as coughing or dyspnea. If the intestinal tract is the primary site of infection, symptoms may be loss of appetite and weight loss. Enlargements in the liver, spleen, and/or lymph nodes, evidence of ulceration, skin lesions, eyes infections, or joint involvement may be noted in generalized cases.
Since the signs of histoplasmosis are often vague and non-specific, a series of screening tests are to be run, including x-rays, urinalysis, and blood tests. Results of these tests will help support a tentative diagnosis of histoplasmosis.
Testing can be done on blood and urine that may detect a component of the fungal cell wall.
There are some limitations to this test: it will cross-react with other fungal species so it may not confirm a diagnosis of histoplasmosis, only a fungal infection; and the test can be falsely
negative if the infection is walled off in one area of the body such as the lungs.
Cytology and/or histopathology are required to diagnose histoplasmosis conclusively. If the
results of cytology are inconclusive, it may be necessary to collect biopsy samples for
Anti-fungal medications are required for several months to successfully treat this disease (4-6
months in most cases).
Pets in poor condition or with advanced disease is less likely to survive. Pets with disease
limited to the lungs tend to respond better to treatment than those with disease of the intestinal tract or other body systems. If the fungus has invaded the eyes or nervous system, it will be much harder to eliminate the infection because of the natural defensive barriers present in these tissues.
Common sense dictates that strict hygiene should be followed when handling any draining
lesions. In most cases, the infected pet does not need to be segregated from the owner or from other household pets. The true risk of infection to others probably comes from sharing the same environment where the original infection occurred (the soil).
By: Chloe - Tisovn Student