In the veterinary world, there sure are a lot of cases of “fungus among us.” This series of blogs will discuss four of the most common systemic fungal infections. Though these four may appear similar in some ways, there are specific differences for pet parents to keep in mind.
The first one we’ll address is blastomycosis, an infection caused by the organism Blastomyces dermatitidis. This organism is found in specific geographic areas – the Mississippi, Tennessee, Ohio and Saint Lawrence river valleys, the middle Atlantic states and the southern Great Lakes. As you may have guessed, it is prevalent near water, as fungal growth is encouraged by wet, sandy soils.
Infection occurs when the spores are inhaled into the lungs. Dogs and humans are most commonly affected, but other animals (like cats and horses) can also contract the disease. However, infection cannot be transmitted from animals to humans, so your pet poses no threat to your family’s health.
After inhalation, the incubation period of blastomycosis is anywhere from five to 12 weeks. The infection progresses to lung disease, which can then spread through the body to other organs including the eyes, bones, skin, lymph nodes and the brain.
Initial, clinical signs of blastomycosis include:
About half of canine cases also have eye abnormalities and in severe cases, secondary glaucoma and blindness can occur. About a quarter to a third of affected animals show lameness due to bony lesions, and some even suffer from pathologic fractures from severe lesions in their bones.
Diagnosis of blastomycosis is made by microscopic observation of the material from draining tracts or from samples taken from enlarged lymph nodes. Biopsy of skin lesions can be very telling, and X-rays of the lungs can show some characteristic findings. In addition, sometimes blood tests are in order to confirm the presence of antibodies against the fungal organism.
The good news about blastomycosis is that the prognosis is generally good. About 50% to 75% of mild to moderate cases recover, although for severe pulmonary cases or when disease has spread to the brain, the numbers are lower. Oral anti-fungal medications are used to treat blastomycosis, but it may take one to two weeks to see improvement in clinical signs. During that time, supportive treatment or hospitalization may be required. Having a dog insurance policy from Petplan can help alleviate the treatment costs.
The prescribed anti-fungals will need to be given for at least 60 to 90 days, and sometimes longer. If blastomycosis is the diagnosis, your veterinarian will likely recommend that you treat your pet for 30 to 60 days more, once the clinical signs of disease are gone.
Stay tuned this week as we discuss other systemic fungal infections.