Blastomycosis
Blastomyces dermatidis is a fungus to which dogs appear to be at least 100 times more susceptible than cats; humans too can become infected. It lives in humid conditions and is often found around bird dropping or rotting vegetation. Hunting and sporting breeds of dogs appear to have an increased risk, possibly related to their aggressive nosing around in soil and under brush.

Infection normally occurs by inhalation of the fungal spores, in rare cases it may occur through inoculation into the skin. Once in the lungs the fungus grows rapidly and then spreads throughout the rest of the body. Signs of the disease may include pneumonia, coughing, fever, weight loss, dyspnoea (problem breathing), lameness from osteomyelitis (bone infection), eye lesions such as uveitis and lymph node (gland) enlargement. Males sometimes get a painful testicular or prostatic enlargement.
Skin lesions (sores) may occur alone or in combination with the other signs and are most common on the face, limbs, around the nail beds and occasionally the tongue. The lesions may range from small abscesses to thickened areas that are ulcerated and exuding fluid (weeping).

X-rays will help indicate the degree of damage in the lungs and if the bones have been affected however these will confirm a diagnosis of blastomycosis infection, as they are not specific. The best methods to confirm a diagnosis is to obtain a sample of affected tissue or fluid and send it to a specialist laboratory for microscopic examination. The sample may be from a skin exudate, a lymph node aspirate (using a needle to withdraw a sample of cells), a tracheal wash (flushing fluid into the windpipe and then withdrawing it) or a biopsy (cutting a small section of tissue out of the affected region).

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.

Blastomycosis will require long term treatment. It is important to realise from the outset that the treatment is expensive and the prognosis is guarded. During this period the animal needs to be restricted so they save their energy. They will need a high quality diet with restricted protein. Pulmonary disease can actually worsen after treatment begins because the dying fungi promote an intense reaction. Relapses are reported at a rate of about 17%, but if the animal is still healthy one year afterwards then they are likely to remain free of the disease.


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