Blastomycosis, or Blasto as it often called, in dogs, humans and other mammals is a commonly misdiagnosed systemic fungal disease. It is a great disease pretender that can be mistaken for cancer, viral infections, Lyme Disease, or other systemic fungal diseases such as Valley Fever. Many dogs die or are euthanized each year due to delay in treatment as the result of a missed or erroneous diagnosis. Involvement of the eye may cause loss of vision or necessitate the removal of the eye. Relapse is also a concern, which is more often reported in female dogs.
Canine Blastomycosis is caused by Blastomyces dermatitidis. This parasitic fungus grows as a mold in moist soil or decaying vegetation and releases spores into the environment that can be inhaled by animals or humans. Young dogs that have access to the outdoors are prime candidates for blastomycosis infection, but infection has been documented in all canine breeds, cats, horses and ferrets. Normally, blastomycosis infection will begin in the lungs after spores are inhaled and transform into large thick-walled budding yeast, which can multiply and disseminate to other areas of the body. Dissemination into organs, lymph nodes, eyes, joints, skin, as well as the central nervous system, is a grave risk.
A diagnosis of Canine Blastomycosis must be made promptly in order to begin treatment with antifungal medications. Unless Blasto is suspected, valuable time is often wasted testing and treating for viral and bacterial infections while the fungus disseminates. Without quick recognition, accurate diagnosis, and access to reasonably priced medications, many animals are unnecessarily lost to Blasto.
Blastomycosis cannot be eradicated from the environment, however, one may attempt to avoid or remove possible sources of contamination, such as mulched areas of flowerbeds, paths, bedding, areas of wetlands, etc. The idea of a commercial fungicide has been discussed, but there are none currently available that are effective against Blasto. With the advent of compounding pharmacies and generic antifungal medications, treatment is now more effective and affordable, making successful outcome for these animals more attainable than ever.
Risk Factors: Endemic Areas, US - Mississippi, Missouri, Ohio River valleys, Eastern Seaboard, areas adjacent to the Great Lakes. States with highest endemnicity are Wisconsin, Minnesota, Missouri, Illinois, Michigan, Kentucky, West Virginia, Arkansas, Tennessee, North Carolina, South Carolina, Louisiana, and Mississippi.
Other endemic states include Indiana, Iowa, Ohio, Virginia, Georgia, and Alabama. However, cases do occur outside the endemic areas. Endemic Areas, Canada - Blasto is prevalent in Kenora, Ontario. Also found in Manitoba, Ontario (Kenora, Sault Ste. Marie, Chapleau), Quebec, New Brunswick, in particular areas around the Great Lakes and in a small area a small area in New York and Canada along the St. Lawrence River. Has also been increasingly reported along the Georgian Bay coastline (including Midland and Penetang), Dryden, and in Southern Ontario at the Rockwood Conservation area.
Environment: Research shows that exposure to wet or decaying organic material, recently disturbed soil, rotting vegetation, bird droppings, and landscaping projects is a strong indicator of disease possibility. Some research has shown a strong link to wood mulch and importation of non-local soil. Patient history will often reveal exposure to mulched areas and disturbed soil in parks, yards, walking paths, etc.
Breed/Age: young, large-breed dogs with the highest rates of infection are normally Coonhounds, Pointers, and Weimaraners. This is normally attributed to higher exposure to endemic areas due to use in hunting. Breed, size, and age, however, are not a reliable indicator of susceptibility, as all are at risk
After initial spore inhalation, incubation can range from days to weeks. The presentation of Blasto is often non-specific, and can imitate a range of other diseases. Symptoms include:
Diagnostic Testing: Diagnosis is based on clinical signs, a thorough patient history, and laboratory findings. Not all findings are specific, some tests are faster and more efficient, and some cases may benefit from antifungal treatment even before definitive diagnosis.
Cytology: New Methylene Blue stain used to identify organisms from exudates of skin abcesses/lesions/sputum/fluid aspirated from lungs appears to be the fastest, most reliable and cost-effective method. Not all cases, however, will present with accessible material, necessitating further diagnostics. MiraVista Diagnostics Antigen Assay: Very high sensitivity with urine (studies show 92.9% sensitivity, specificity 79.3%), slightly less sensitive with serum. 4-5 days for results, at a cost of approx. $100. Also useful in monitoring the efficacy of antifungal therapy. Chest X-Ray and signature snowstorm pattern. Area Bone Radiograph Lymph node biopsy / fine needle aspiration. Serum Antibody Titer: regarded as a fairly poor diagnostic tool for Blastomycosis. Tracheal wash. Ultrasound
Be Aggressive: Excerpt: Journal of Clinical Microbiology, October 2004, p. 4873-4875, Vol. 42, No. 10.
Most patients with blastomycosis exhibit progressive illnesses that require antifungal therapy. In one study, diagnosis was delayed for more than 1 month in nearly half of the cases. Blastomycosis was correctly suspected in only 20% of patients, resulting in unnecessary surgeries and treatment delays. In two-thirds of patients who died of acute respiratory distress syndrome caused by blastomycosis, the diagnosis was either not suspected or considered only after the patient became moribund.
In the past, Amphotericin-B was the only known medication useful against Blastomycosis and the other systemic fungal organisms. It was given intravenously and with care to keep the dose from harming the kidneys.
More recently, research has provided oral azoles that are highly effective in treating fungal infections. Itraconazole (Sporanox), Ketoconazole (Nizoral), and Fluconazole (Diflucan) are available as capsules and oral suspensions that may be administered for 3 to 6 months (depending on the severity of infection, treatment may be even longer).
Compounding pharmacies have made these medications much more affordable and available in custom dosages for different sized animals. Generic and brand name medications are equally effective, and given the very high cost of brand names, the generic compounded alternatives are saving lives that may have previously been lost due to the cost and length of treatment.
Treatment: Once Blasto is diagnosed or is highly suspected, treatment can be started with the appropriate antifungal medication. In the early stages of treatment large numbers of fungi begin to die in the lungs and often elicit an inflammatory response. Prednisone is sometimes prescribed to help reduce inflammation issues. Many of these animals are fighting a fungal pneumonia. As a result, respiratory distress is often a significant problem in the first few days following initiation of therapy. Since the severity of the infection will determine the amount of fungi inhabiting the dog’s lungs, early diagnosis and treatment is an efficient means of reducing post-treatment respiratory distress and can significantly influence a dog’s chances of survival.
The animal’s prognosis will always be guarded, and antifungal treatment is never a guarantee of recovery. Intense supportive care and a high level of commitment to recovery on the part of the owner are imperative. Round the clock care is often necessary. Removal to a medical facility for IV treatment and hydration may be helpful and sometimes unavoidable, but can be very stressful for a compromised animal. If the owners are able to provide care, the security of home and loved ones may reduce stress. The outcome will also vary with the degree of infection, whether Blasto has disseminated into other organs, CNS, bones, or in the event of secondary bacterial or viral infection.
Eye involvement may result in blindness or necessitate removal of eye(s). Recently some experimental treatments have reported some success in the nominal recovery of vision. These treatments can be fairly expensive, and are not a guarantee of sight recovery. (**See Dogs In Canada, by Rick Hayworth.)
During the first few weeks of therapy, the animal may become alarmingly ill, anorexic, and may have to be force-fed. Weight loss may continue; hydration and calories are important. During this time, the idea of eating healthy may need to be suspended in favor of getting any nutrition possible into the animal. Owners who have successfully treated their animals recommend the following:
Medication: Sources and Cost: Antifungal prescriptions from retail pharmacies can range from $4 to $9 per dose. As treatment must be continued for as long as 12 months, cost will be an issue that affects the owners’ decision regarding treatment vs. euthanasia. Compounding pharmacies have made generic and custom doses much more affordable. For example, the cost of generic Itraconazole 150 mg. from Pet Health Pharmacy in Arizona is approximately $1 per dose. Overnight shipping is available at a cost of about $8-$10 extra. These medications appear to be equally effective as brand name varieties and make the option of treatment more feasible for the owner.