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Blastomycosis is a fungal infection caused by the fungus Blastomyces dermatitidis. This fungus is commonly found in the river valleys of Tennessee, St. Lawrence, Ohio, Mississippi and Missouri as well as the southern Mid-Atlantic States.

Exposure to this organism usually occurs within areas close to waterways as well as in areas where the ground has recently been disturbed. This is because the fungus lives in the soil and once the soil has been disturbed, the fungus becomes airborne and can be inhaled. Inhalation is the primary route of infection. This disease cannot normally be transmitted from your pet to you; however, you can be exposed to the organism in the same environment that your pet was exposed and should seek out the advice of a physician if any symptoms develop.

Once inhaled, the spores of the fungus can spread to other parts of the body. Some of the clinical signs you may notice in your pet include the following:

Eyes: Redness, discharge, swelling, squinting, elevation of the third eyelid, and blindness. These are very nonspecial 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). Oftentimes, ocular disease is the only sign of infection with Blastomycosis. Fifty percent of dogs with ocular lesions have the disease in both eyes.

Skin: Few to several draining or crusting skin lesions that are slow to heal.

Respiratory System: Coughing or increased effort to breath.

Other: Decreased appetite, weight loss, fever, lameness, enlargement of lymph nodes and changes in mentation (neurologic abnormalities), which are more often observed in cats.

Dogs are about 10 times more likely than humans, and 100 times more likely than cats, to become infected. The typical Blastomycosis patient is a large breed, male dog that spends a lot of time outdoors.

On average, it can take 5-12 weeks from the time of infection to the development of clinical signs (incubation time).

Diagnosis of Blastomycosis:

Depending on the clinical signs your pet is showing, your doctor may recommend certain tests over others. Blood, urine and skin lesion samples are commonly obtained. Sometimes a sample may be directly taken 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; if lung lesions are present, their resolution can be used to determine how long treatment will be necessary.

Treatment of Blastomycosis:

The treatment of choice is the oral antifungal, Itraconazole. Depending on the severity of clinical signs, your doctor may recommend treatment for up to 9 months. While Itraconazole is a very safe drug, side effects may include liver disease and gastrointestinal upset. For these reasons, we recommend regular bloodwork to monitor for any side effects than may require adjusting the amount of medication.

Appropriate treatment for the eyes often includes anti-inflammatory eye drops as well as anti-glaucoma medications. 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; if this is the case, your doctor will explain the options available for your pet.

General supportive care may be necessary. Your doctor will work together with your referring veterinarian to make sure your pet is getting complete treatment.


Although many dogs will lose their vision following this infection, they will often recover from Blastomycosis and live healthy and happy lives following treatment. While most dogs do not have recurrence of the disease, it is possible; that is why it is very important to monitor for any of the above clinical signs and see your veterinarian as soon as possible if you notice anything abnormal. Although very rare, some dogs do not survive infection with Blastomycosis.


Be mindful of when and where you decide to go hiking in the woods, especially near waterways and areas of signigficant ground disturbance, as is common with construction sites. Even super special digging of the ground by your dog can release the infectious spores into the air. Become familiar with the clinical signs mentioned above and talk to your doctor. If you are ever in doubt, do not hesitate to ask.

If you have any question about this information please contact your veterinarian.