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Outdoor Enthusiasts Take Note: Beware of Blastomycosis

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MADISON — It's an uncommon but potentially serious illness often mistaken for pneumonia. Even if you don't get ill, it could sicken or even kill your dog. And the risk comes from the soil, so avoiding it during outdoor activities may be impossible.

Blastomycosis is a fungal infection originating from soil that is contaminated from decomposed debris, animal carcasses or excrement. Although overall it affects humans infrequently, those who love the outdoors can encounter "blasto" in camping, fishing and hunting areas close to water and the dogs that often trot along with the humans are quite susceptible also. Disturbing contaminated soil releases the fungal spores into the air.

Tainted earth linked to the infection has been found in many areas of North America including the Midwest, Ohio/Mississippi River Valley, southeastern Atlantic and southern Canada.

Most states don't keep statistics on blastomycosis, although the Wisconsin Department of Public Health says an average of 86 cases were reportedly annually in the mid-to-late 1990s. The infection is not contagious and can't be passed to other humans.

According to Dr. Bruce Klein, professor of pediatrics and an infectious-disease researcher at the University of Wisconsin School of Medicine and Public Health, blastomycosis begins after a person inhales spores that come out of the contaminated soil.

"In the lungs, the spores cause an infection that may enter the bloodstream, skin, bone, urinary tract, and central nervous system. Patients can get very sick," he says.

Symptoms are similar to pneumonia: a dry cough and fever leading to muscle aches; night sweats; coughing up blood; shortness of breath; and chest tightness. If the infection is diagnosed and treated promptly, 90 percent of patients fully recover.

The problem is the incubation period may take up to three and a half months, and people who think they have other common forms of pneumonia may actually have blastomycosis, which is far more serious.

According to Klein, the most common drugs used to eradicate blastomycosis are amphotericin B and a class of medications called azoles. Patients may have to take them up to a year, and they come with possible side effects.

"Ampho B may cause anemia, impairment in kidneys, chills, shaking, nausea and vomiting," says Klein. "Azoles may cause gastro-intestinal side effects and liver damage."

"Sometimes, it becomes a balancing act on how to reduce the medication and its side effects, while at the same time, giving the patient enough so it treats the infection."

Klein and others are researching other drugs to treat blastomycosis. While a vaccine is not available for humans, there have been positive results in experiments with animals.

"A vaccine we developed has been working very well on the mice we studied," says Klein. "We are still trying to understand how it works."

Klein says mice infected with blastomycosis survived after being injected with the experimental vaccine. Without the treatment, they all would've died within three weeks.

Other tests are being conducted on dogs, which have been known to catch the infection during hunting, fishing or camping trips with human companions. Klein says a study in northern Wisconsin determined that up to two percent of dogs acquired the blastomycosis fungus each year, and nearly two-thirds died or were euthanized after the infection was impossible or too costly to treat. Fortunately, dogs cannot pass blasto to humans.

In the meantime, Klein says there's no way to avoid the infection, but adults and children should not be discouraged from participating in outdoor activities.

"We aren't clear on specific recommendations to avoid the risks of getting this infection," he says. "However, if someone gets a case of pneumonia where antibiotics have not worked, and they had been traveling in an area that's endemic for blastomycosis, the disease should be considered by their physician."
 

Date Published: 04/27/2009

News tag(s):  bruce s klein

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