Article June 2010

Dear Doctor: My dog is coughing, not eating well and has a fever. The vet wants to test him for Blastomycosis, but it sounds like the testing is expensive - can you tell me more about this infection?

Signed,
John in Plover

Blastomycosis is a fungal infection that can affect many mammals, including dogs and humans. I am also aware of a case in an indoor cat. The organism prefers moist areas in the environment, such as along water beds, compost piles, and wood piles. The organism may be present one day in a particular area, and seemingly gone the next day, based on environmental conditions.

Dogs seem to be particularly susceptible to infection due to their propensity to sniff the ground, inhaling the fungal spores into the lungs. The majority of the cases will develop pneumonia; however, not all dogs will have the infection remain in their lungs. I have had a case where the only symptom was a lesion on the skin, and another dog with a fever and vaginal discharge. It is not unusual for pets to develop inflammation within the eyes caused by the infection, which can lead to blindness. I had one patient with lameness and infection in the bone. No two cases are the same in terms of symptoms, progression of disease, or response to treatment.

The infection can be difficult to detect, with suspicion increased after the discovery of pneumonia in the lungs. In the absence of pneumonia, I usually suspect Blastomycosis in any pet that has a fever and poor appetite. The ideal way to diagnose the infection is to find the fungal organism in any body tissue or fluid; the organism has a characteristic shape when viewed under a microscope. However, it is not always possible to find the infection microscopically, so we will also look at other laboratory tests of blood and urine. I have had several cases that were eventually confirmed as Blastomycosis that had a "negative" blood test, which can be frustrating for everyone involved. Recently, a test that screens the urine was made available, with a much greater sensitivity than the standard blood test. The urine test is indicated in cases that do not even have any urinary symptoms.

If one of the tests is positive, then treatment can begin. Treatment generally includes a prolonged course of anti-fungal medications, given for a minimum of 4 to 6 months. The urine test can be used to gauge response to treatment, along with follow-up x-rays, if indicated. Unfortunately, not all dogs will respond well to medication, especially if treatment is delayed. Of those that do respond, a small percentage may relapse within the year, requiring an additional treatment course. Considering the diagnostics and treatments involved, the disease can be very expensive to manage properly.

If your vet believes your dog has enough symptoms to warrant testing, time is of the essence. If the disease is confirmed, than you can start treatment. If the disease is not detected, than your vet may need to pursue additional testing to rule-out other diseases with similar symptoms.

I understand how frustrating it can be to wait for the all of the test results, but continue to work with your vet to find the right diagnosis. Best wishes for the health of your pet - I hope you find your answers soon!