By Dr. Becker
Blastomycosis is a systemic fungal infection caused by Blastomyces dermatitidis, an organism that grows in rotting wood and wet soil.
The Blastomyces fungus thrives in wet environments like swamps, lakes, and on riverbanks where damp soil and lack of direct sunlight encourage its growth. The fungus is also found in locations that harbor decaying organic matter like wooded areas, forests, and farms. Blastomycosis infections are prevalent in locations near water, including the Mississippi, Ohio, Missouri, and Tennessee River basins.
Pets at Highest Risk for Blastomycosis
The infection is seen most often in large breed male dogs, and especially in hunting dogs, sporting breeds, and dogs that spend a lot of time in environments where the Blastomyces organism exists. Female dogs are also susceptible, of course. And occasionally, cats also acquire the infection.
Studies indicate most dogs that acquire a blastomycosis infection live within a quarter mile of a body of water.
Methods of Transmission
The fungus releases airborne spores into the environment that can be inhaled by people and animals. This is the most frequent method of transmission, though the spores can also enter through the skin. In fact, just digging in the soil can release the spores. Once inhaled, the spores travel through the lungs and become large, thick-walled, yeast-like organisms that multiply within the lungs and other tissues of the body.
Blasto is known as a dimorphic pathogen, meaning it occurs in two distinct forms: it grows as a mold in the environment, and as yeast in tissue. Blastomycosis has the potential to cause significant pulmonary disease. The yeast also tends to travel to other sites in the body, especially the skin, eyes, and joints.
If your dog has a blastomycosis infection, he can't directly infect other members of the family – humans or pets. However, care should be taken when handling any secretions. For example, in draining lesions, you should use protective gloves and wash your hands thoroughly after you've had contact with your infected pet's sores.
There's no need to isolate infected pets from other family members. However, you should take care to avoid the area where your dog likely picked up the Blastomyces spores. This is particularly important for infants and toddlers, elderly family members, and anyone who is immunocompromised.
Symptoms and Diagnosis
Symptoms of blastomycosis infection in dogs include loss of appetite, fever, weight loss, depression, inflammation of the iris of the eye and discharge from the eyes as well, coughing, wheezing, and pus-filled skin lesions. More serious symptoms can include sudden blindness, lameness, inflammation of the testicles, enlarged lymph nodes, and seizures.
Unfortunately, blastomycosis is often misdiagnosed -- even by the best veterinarians --sometimes as cancer and sometimes as a bacterial lung infection. Needless to say, treatments for cancer and antibiotics for bacterial infections will not address the fungal infection and can lead to permanent damage or even death, if your pet doesn't get an accurate diagnosis.
If your dog has been showing any of the above symptoms for six weeks or more with no noticeable improvement, and if he could have been in an environment that harbored the Blastomyces fungus, your veterinarian should test for a fungal infection.
Blastomycosis is best diagnosed through examination of a lymph node, a fluid drain from skin lesions by a transtracheal wash, or by examining lung tissue. Tissue samples may need to be taken to check for fungal organisms.
There's also a blood test called an AGID test or antigen ID test for exposure to Blasto. But a positive result doesn't mean your dog necessarily has the infection, only that he's been exposed.
Chest X-rays of a dog with blastomycosis often reveal a sort of snowstorm-type pattern. Urine screening tests can also be very beneficial for diagnosis.
Traditional treatment for a blastomycosis infection is oral administration of an antifungal drug. These medications all require long-term treatment, sometimes for many months. They are very expensive. And of course, all of them carry serious potential side effects.
The preferred antifungal at the moment for dogs diagnosed with this infection is Itraconazole, which is better tolerated and has fewer side effects than older antifungal drugs. I also recommend a nutraceutical called quantum nucleotide, which helps to stimulate an immediate immune system reaction, as well as oil of oregano in capsule form, which is excellent support for a body fighting a fungal infection.
For many dogs, the critical period during treatment is the first 24 to 72 hours, as the antifungal drug begins to kick in and kill off the fungi. Since there are typically a large number of organisms in the lungs, there can be an overwhelming inflammatory response that can result as the fungi die off. Respiratory distress can be a big problem during the first few days of treatment.
Whatever drug is used, it must be given for a full month past all signs of infection. Dogs with severe breathing difficulties may require supplemental oxygen until their lungs return to normal function.
Blastomycosis is a serious fungal infection. The sooner you seek treatment, the better chance your dog has to fully recover.