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Blastomycosis: Questions & Answers

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What is blastomycosis?

Blastomycosis is a fungal infection that is caused by the fungus Blastomyces dermatidis. It is usually caused by inhaling airborne spores (fungus) from contaminated soil or decaying matter (e.g., damp or rotting wood and leaves). It is most common in the spring and in the fall. As the ground becomes covered for the winter, it becomes less likely that the contaminated soil is disturbed.

When an individual breathes in the spores, they can enter and settle in the lungs, causing an infection. These spores can become airborne after the contaminated soil is disturbed (e.g., digging, excavation, construction, wood clearing). Both animals and humans can become infected with blastomycosis.

How does blastomycosis spread?

Blastomycosis is NOT spread from person-to person, and it does NOT spread animal-to-person. The spores must be inhaled from contaminated soil into the lungs. Less common, the airborne fungus can settle in an open would, and this would cause an infection in only that area of the body.

What are the symptoms of blastomycosis?

The symptoms of blastomycosis can vary and be mild to severe. Many individuals will not develop any symptoms, or they may only have only mild symptoms that will go away without treatment. Symptoms can appear between three and fifteen weeks after exposure. This can make it difficult to determine where the individual may have been exposed to the fungus. Some individuals have more severe symptoms and may develop pneumonia requiring timely treatment and possibly hospitalization. Left untreated, severe cases of blastomycosis can eventually progress to death.

In humans, the most common symptoms include:

  • Cough (sometimes with blood)
  • Fever
  • Shortness of breath, pneumonia
  • Chills and/or night sweats
  • Weight loss and poor appetite

In animals, the most common symptoms include:

  • Fever
  • Cough
  • Difficulty breathing
  • Weight loss
  • Skin lesions

What is the incubation period of blastomycosis?

The incubation period is the number of days between when an individual is infected with something and when they might start developing symptoms. The incubation period for blastomycosis can vary between 21 to 106 days.

What is the treatment for blastomycosis?

In most individuals, the illness is mild and does not require any treatment. Some individuals (especially those who are immunocompromised), may develop more severe symptoms and require an anti-fungal therapy. Since blastomycosis is a fungal infection, the required treatment is an anti-fungal medication that is taken for at least six months. Antibiotics cannot be used to treat blastomycosis.

What should I do if I have symptoms?

It is important that both humans and animals seek medical attention from a health care provider or veterinarian as soon as symptoms appear. Let your health care provider know that you have been in an area where blastomycosis has been found. Early diagnosis and treatment help to prevent severe infection and illness.

How is blastomycosis diagnosed?

Depending on the symptoms, blastomycosis can be diagnosed with different types of lab tests (blood, saliva, urine, or skin lesions). A chest x-ray may also help diagnose blastomycosis.

What can I do to protect myself from blastomycosis?

Blastomycosis is a rare infection, and even if you live in an area where the fungus grows, the risk of getting it is low. In areas where there is known blastomycosis, individuals with a weakened immune system should avoid activities that would require working with the soil.

Spending time outdoors will not increase your risk of blastomycosis, however at this time, digging, clear cutting and excavating in the area should be avoided.