Blastomycosis reports in dogs increasing in northern Minnesota

Cases of a severe fungal infection called blastomycosis are increasing along the North Shore and areas of northern Minnesota. 

Blastomycosis is an infection caused by a fungus called blastomyces and can infect humans and animals. It is commonly found in the northern regions of Minnesota and along areas such as the St. Croix River, Mississippi River, and surrounding Great Lakes. According to the Minnesota Department of Health, the infection usually occurs by breathing in spores of the fungi that are generally found in moist soils, particularly in wooded areas, such as boreal forests and along waterways. 

“In terms of recent trends, we’re actually seeing a lot more blastomycosis cases in both animals and people over the past five to six years,” said Malia Ireland, a senior epidemiologist with the Minnesota Department of Health.

Prior to 2016, Ireland said the median number of blastomycosis cases for animals was approximately 100 per year. However, since then, the median number of cases has risen to 200-250.

While the Minnesota Department of Health has not finalized the data for 2022, Ireland said, “We will probably end up with over 400 cases in the whole state in 2022.”

The increase in blastomycosis can be attributed to better overall reporting, Ireland explained. However, environmental conditions such as increased precipitation and flooding play a significant role. 

Northern Minnesota, and in particular, Cook County, experienced significant flooding in May of 2022 and again during the spring of 2023. “So that may have increased the range where this fungus can thrive in the soil,” Ireland said.

Of the approximately 400 blastomycosis cases in animals reported in Minnesota for 2022, Cook County had three confirmed cases. So far, in 2023, the Minnesota Department of Health has received four blastomycosis cases in Cook County dogs. While that is not a significant increase in Cook County, it is something to be aware of. 

Cedar Grove Veterinary Clinic in Grand Marais has diagnosed two cases of blastomycosis in recent weeks. Nadder Samari, the owner and veterinarian at Cedar Grove Veterinary Clinic, said since the clinic’s establishment seven years ago, he has treated 25 dogs for blastomycosis. “Having 25 cases in seven years is a large number, and it seems to be growing.”

A portion of the 25 dogs treated for blastomycosis at the veterinary clinic live in Thunder Bay, Canada, and travel to Grand Marais to receive treatment. Although a few Canadian provinces report on blastomycosis, the Canadian government states the true incidence of blastomycosis is unknown, as it is not reportable nationally in Canada. 

The United States also has limited reporting of blastomycosis and is currently only reportable in people in five states, including Minnesota, Wisconsin, Michigan, Arkansas, and Louisiana. “It’s really an understudied infection,” Ireland said. 

Once a dog or animal has contracted blastomycosis, symptoms include loss of appetite, skin lesions, limping, cough, weight loss, respiratory problems, and blindness. Samari said symptoms may take a while to present, as the incubation period for blastomycosis is four to six weeks. “The fungus can remain dormant in the body for several months, or even years, and can manifest itself due to a stressful situation or another illness.”

Testing for blastomycosis is relatively easy and highly accurate, Samari said, and requires a urine sample. If a dog or animal does test positive for blastomycosis, the infection is not contagious to other dogs or humans. 

Fortunately, treatment is available, although it may be a lengthy process. “If we catch it early, the dog owners have to commit to a minimum of three to four months of treatment, sometimes six months,” Samari said. If left untreated, however, blastomycosis can be fatal. Of the 220 animals reported to have contracted blastomycosis in 2021, 21 percent were euthanized or had died. “Catching it early is the key.”

“Awareness is the best prevention,” Ireland said. Being aware that the fungus does exist in moist soil and wooded areas in northern Minnesota is half the battle. The Minnesota Department of Health states that while there are currently no methods to test soil for blastomyces, preventative measures include minimizing recreational use in areas with recent flooding, excavation, or regions with moist organic matter.

WTIP’s Kalli Hawkins spoke with Malia Ireland, a senior epidemiologist with the Minnesota Department of Health, and Dr. Nadder Samari, the owner and veterinarian at Cedar Grove Veterinary Clinic, about the increase in Cook County and Minnesota reported cases of blastomycosis in dogs. Audio below. 

Kalli Hawkins September 29, 2023