Histoplasmosis
P>Histoplasma capsulatum is a fungus that can either be inhaled or eaten. The fungus lives in the soil, preferring humid climates, and will grow profusely in chicken, bat and wild bird droppings. It can infect both cats and dogs. Hunting and sporting breeds tend to have an increased risk, thought to be due to their active nosing around in soil and under brush.

Most animals with this disease present with anorexia, weight loss, weakness, dyspnoea (difficulty breathing) and a cough. Some may have lymphadenopathy (enlarged lymph glands), hepatomegaly (enlarged liver), chorioretinitis (inflammation of the retina and iris), bone swellings and skin sores. Dogs are also likely to have watery to bloody diarrhea, tenesmus (ineffectual and painful attempts to defecate) and blood or mucus in the feces. Some rare cases may get an infection in the central nervous system (brain and spinal cord).

The best method to confirm a diagnosis is to obtain a biopsy (small sample of tissue) and send it to a specialist laboratory for microscopic examination. Blood tests may indicate damage to individual organs the presence of infection but are not specific for Histoplasma. X-rays will help identify lesions in the lungs and bones.

Histoplasmosis will require long term treatment. It is important to realize from the outset that the treatment is expensive and the prognosis is guarded, cats in particular have a grave prognosis. During this period the animal needs to be restricted so they save their energy. They will need a high quality diet with restricted protein. There is always a chance of a relapse after therapy has finished, some times up to a year after apparently successful treatment.

Drugs available from treatments include amphoteracin B (AMB), ketoconazole (KTZ) and itraconazole (ITZ). Animals vary in their response to these so the treatments may need to be altered accordingly. Side effects are a significant problem. Renal (kidney) dysfunction, inappetence, fever phlebitis (inflammation of the veins) and vomiting have been observed with AMB therapy. The side effects of KTZ and ITZ include inappetence, vomiting and liver damage, although ITZ is reported to have less of these side effects. Blood tests for liver and kidney function need to be performed regularly to ensure these side effects do not become a significant problem.

There is no vaccine available for this disease. Owners are advised not to let their animals roam or hunt in regions where histoplasma is known to be a problem.