Blastomycosis and your pet
Blastomycosis is a fungal disease that we see about once a month here in Marquette, Michigan and early detection is the key to beating this dreaded disease. Let’s learn a bit about it.
Blasto is a fungal infection that usually starts in the lungs and then spreads to other parts of the body. Dogs and cats are both susceptible, but the disease occurs most often in dogs. I have seen one case ever in a cat to date.
Blastomycosis(the disease) is caused by the fungus Blastomyces dermatitidis . It is an organism that grows in dead or decaying organic matter in the soil. It can survive in a wide range of moisture and temperatures but prefers loamy, moist soil, especially along water bodies. In the United States, it occurs most commonly in the Ohio, Mississippi, Missouri, Tennessee and St. Lawrence River valleys. It can also be found in the southern Great Lakes region and in the mid-Atlantic states. 2 other areas of great prevalence are Northern Minnesota, Northern Wisconsin and the Upper Peninsula of Michigan.
Infection occurs most commonly via inhalation or ingestion of the fungus from the environment. Infection may be limited to the lungs or may spread to multiple sites in the body. Often these dogs will have been exposed to a recently excavated area such as basement, hole for the septic system, ditch or new road.
Signs may initially be nonspecific and include lethargy, decreased appetite, and weight loss. Increased respiratory rate, difficulty breathing, and coughing may occur. Inflammation of the eyes,vision changes, enlarged lymph nodes (glands), and lameness from bony involvement are other possible signs. A fever that doesn’t respond to normal antibiotic protocols is a big red flag. Skin lesions occur in about half of the cases and are usually crusty bumps that drain a thick liquid. Organisms present in this liquid may spread the infection if it contaminates an open wound.
How do we diagnosis it?
Routine laboratory tests and chest x-rays are commonly recommended to investigate the clinical signs. X-rays of the legs may be done if lameness and bone pain are present. Blood tests are available for blastomycosis at certain outside laboratories but are unreliable and I do not recommend these as the false negatives are too high. There is now an urine test that has a much higher rate of true positives that we utilize both at diagnosis and knowing when to stop the medications.
Finding the organism in affected tissues is the best diagnostic test. Needle aspiration or biopsy of an enlarged lymph node, skin lesion, blind eye, or other affected tissue may be done. A tracheal wash, collecting fluid from the airway or coughed up fluid can be used if the lungs are involved.
Drugs, such as itraconazole and fluconazole, are generally considered effective but must be given for a prolonged period of many months, often 6 or more. These are expensive medications. Seriously ill animals often require hospitalization, with intensive treatment and monitoring for the first week or so of treatment. Dogs with severe lung disease may need supplemental
oxygen. Death of the fungal organisms that occurs within the first few days of therapy may make the lung changes temporarily
worse leading to rapid fluid build up that can compromise breathing. These are tough cases with a success rate that is not high.
Once released recheck visits are required often for several months to monitor the response to treatment and for
side effects of the medications. Treatment is continued for at least 4-6 months, and for 1 month beyond the disappearance of all clinical signs and a negative urine blasto test.
Prognosis is variable and depends on the extent and severity of the disease, as well as the initial response to treatment. They can get better only to relapse again. Prognosis is better in animals with mild clinical signs. Prognosis is guarded (uncertain) in animals with widespread disease, central nervous system involvement, or severe involvement of any organ system.
So, things to remember with this disease are 1. coughing dog, especially one with a low grade fever that is non responsive to normal antibiotic regimens. 2. Skin lesions that are draining. 3. Fever of unknown origin cases.
Early detection and treatment are key to these animals surviving and in areas where it is common it is on your radar. In areas where it is not it can be missed or if the dog traveled in an area known to harbor this disease. We just see too much of this and it is nobodies fault, it is around.