Blastomycosis is an infection caused by the fungus Blastomyces dermatitidis. This fungus is commonly found in Tennessee, southern mid-Atlantic states, Mississippi, Missouri and the Ohio river valley. Within these regions, exposure is most common in areas close to waterways such as lakes or rivers. Blastomycosis can infect a wide variety of animals, including humans. Therefore, it is important to seek a physician if you or your pet develops any signs of this disease.
On average, it takes 5-12 weeks from the time of infection to the development of clinical signs. Infection occurs by inhalation. Once inhaled, spores from this fungus can infect the lungs and then spread to other parts of the body. Blastomycosis can cause a wide variety of clinical signs, which may include the following:
Eyes: Redness, cloudiness, discharge, swelling, squinting, elevation of the third eyelid, and blindness. These are very nonspecific signs and may be indicative of a different disease process as well. The disease can cause inflammation inside of the eye leading to retinal detachment and glaucoma (see glaucoma handout). Occasionally, eye disease will be the only clinical sign of this fungus. Fifty percent of dogs with ocular blastomycosis will only have one eye affected.
Skin: draining and/or crusted lesions that are slow to heal.
Respiratory System: Coughing or increased effort to breath.
Other: Decreased appetite, weight loss, fever, limping, enlargement of lymph nodes and behavioral/ neurologic changes.
Dogs are about 10 times more likely than humans and 100 times more likely than cats to become infected. Fortunately, infected pets and people are not contagious. The typical Blastomycosis patient is a large breed male dog that spends a lot of time outdoors and near lakes or other bodies of water. However, any animal that lives in the regions noted above may become infected.
DIAGNOSIS OF BLASTOMYCOSIS:
Your veterinarian will recommend diagnostic testing based on the specific clinical signs your pet is showing. Samples from blood, urine and/or skin lesions (if present) are commonly obtained. Radiographs (X-rays) and/or ultrasound are often needed to search for signs of systemic blastomycosis infection. Occasionally, it is recommended to obtain samples directly from the eye.
To further evaluate the extent of the disease your doctor may recommend chest radiographs or X-rays. This is because lung lesions can be present without clinical signs and if lung lesions are present their resolution can be used to determine how long treatment will be necessary.
TREATMENT OF BLASTOMYCOSIS:
Most forms of Blastomycosis are treated using an antifungal called Itraconazole. However, different antifungals are occasionally indicated. Duration of treatment can vary, and is occasionally necessary for close to 1 year. Itraconazole tends to be a very safe drug, however, side effects may include liver disease and gastrointestinal upset (ie decreased appetite, vomiting, diarrhea). For this reason, we recommend regular blood work to monitor for any potential side-effects.
If the eyes are infected, additional treatments such as anti-inflammatory eye drops and/or anti-glaucoma medications may be indicated. Depending on the severity of clinical signs and inflammation within the eye, medical therapy may or may not be successful in keeping your pet visual and/or comfortable. At that point, surgical therapy may be required and your doctor will explain the options available for your pet.
General supportive care may be necessary and your pet's ophthalmologist will work closely with your referring veterinarian to make sure your pet is getting complete and appropriate treatment.
PROGNOSIS:
When Blastomycosis affects the eye, it can be very serious and has the potential to cause permanent blindness. Fortunately, with the appropriate treatment, most dogs (including those that lose vision) are able to fight off the systemic fungus and have healthy and happy lives. After recovery, dogs have an approximately 20% chance of relapse. Therefore, it is very important to monitor your pet for any of the above clinical signs and to call your veterinarian as soon as possible if you notice any of them. Although very rare, some dogs never recover from Blastomycosis.
PREVENTION:
Unfortunately, there are no vaccinations available for Blastomycosis. It is therefore important to become familiar with the clinical signs mentioned above and to contact your veterinarian if signs occur, as being proactive will give the best chance for recovery.
If you have further questions about blastomycosis in your pet, please call us at Eye Care for Animals.
