What is Blastomycosis?

board of animal health

Reportable Disease of the Month


What is it?

An infection caused by the mold form of fungi in the genus Blastomycyes. The fungus grows in moist soils and decaying vegetation and therefore thrives in wooded areas and near water. Geographic areas near the Great Lakes and Mississippi and Ohio River basins are common areas of concern. Blastomycosis frequently infects people and dogs, but cats, horses and wildlife are also at risk. In Minnesota, cases are typically identified in northern counties, but infected animals have been reported in almost every county. In 2016, 140 animal cases were reported, the highest in any recorded year to date.

How is it transmitted?

Blastomycosis infection usually occurs when an animal or person inhales spores from soil where the fungus is present. Less often, infection occurs from direct inoculation of spores into a wound or a break in the skin. Transmission from animal-to-animal or animal-to-person is very rare as the fungus is in a less infective (yeast) form when in a host.

What are the clinical signs?

Signs may include fever, loss of appetite, weight loss, cough, difficulty breathing, lameness, eye disease and skin lesions. Infection typically starts in the lungs and can spread to many organs throughout the body including lymph nodes, eyes, skin and bone.

How is it diagnosed?

Microscopic examination of samples collected from infected tissues or sputum can reveal the fungus. Laboratory blood and urine tests are available, and chest x-rays can show lesions in the lungs.

Is there a risk to people?

People can become infected with blastomycosis by inhaling spores from soil where the fungus is growing. People are not at risk of contracting blastomycosis directly from an animal. However, if a pet is infected it is likely that the pet owner has also been exposed.

How can it be prevented?

Prevention proves difficult as the fungus cannot be eliminated from the environment and soil testing is not validated. Education and early diagnosis and treatment are the best methods for reducing infection.

How can you report it?

Remember, blastomycosis is a reportable disease. The Minnesota Department of Health recently updated its reporting form, which is a fillable PDF file. Please click this link to access it and report canine cases. There is also a reporting form for human cases, which can be found on the Department of Health website by clicking this link.

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