DULUTH — Cases of a serious and sometimes fatal fungal disease in Minnesota dogs are off the charts so far in 2019 as blastomycosis spreads in a wetter, warmer climate.

So far in 2019 there have been 170 cases of blastomycosis in dogs reported to state health officials, up nearly 50% from last year at this time and already topping the previous record of 155 set in all of 2017.

Exposure to the fungus starts in the spring, with reports peaking in October and slowing after snow falls.

“It’s already the most cases we’ve ever had, and we still have a few months to go. We usually get our most reports during September, October and November,” said Malia Ireland, a veterinarian and epidemiologist for the Minnesota Department of Health who keeps track of the disease in the state.

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State health officials reported earlier this month that blasto cases are way up in humans this summer as well. Most blasto exposure for Minnesota dogs and people appears to come from northern counties.

Blastomyces spores thrive moist soils with decomposing organic materials, so heavily forested areas are prime spots for outbreaks. Ireland and others speculate the big increase in cases is because of more heavy rain events that bring high water flows and flooding, exposing soils that carry the fungal spores that cause blastomycosis.

“It seems we get quite a few reports near creeks and rivers that have flooded sometime in the recent past,” Ireland said.

But blasto also shows up in damper soils not near any waterway, and the number of cases reported in Minnesota has been increasing nearly every year in recent decades. Ireland said it’s not clear if that’s because there are more cases diagnosed, because there’s more blastomycosis spores in the soil, or both.

Twin Cities veterinarian Jeff Bender started to pay close attention to blasto in 1995 and pushed to have it declared a formally reportable disease in 1997 when he worked for the Minnesota Department of Health. Now with the University of Minnesota School of Public Health and an expert on diseases that impact both animals and humans, Bender credits this summer’s record blasto outbreak to both increased awareness and climatological conditions.

More dog owners know what to look for — lethargy, loss of appetite, coughing and sores on the skin or eyes — and more vets know to test for it. But he also believes it’s warmer, wetter weather that has triggered this year's outbreak.

“It’s a fungus that likes warm, wet or humid weather,” he said. “It’s endemic in the soil; it’s always there. But under the right conditions, and we’ve certainly had those this year, it grows. It becomes more prevalent.”

Medicine usually works, but some dogs die

There is no vaccine for blasto (for humans or dogs) and no way to test soils for the dangerous fungal spores, Ireland noted. Blasto has proven maddeningly difficult to study in the lab where scientists can’t get it to grow like it does in nature.

“The best defense is awareness. Avoiding disturbed soils in that blasto belt area in (northeastern Minnesota) and then knowing what to look for when it hits,’’ Bender said. "They you have to act fast."

Drake, a black lab owned by Casey Sunsdahl of Soudan, developed blastomycosis and battled the fungal disease for nearly 18 months at a cost of over $5,000 for his owner. Photo courtesy Casey Sunsdahl.
Drake, a black lab owned by Casey Sunsdahl of Soudan, developed blastomycosis and battled the fungal disease for nearly 18 months at a cost of over $5,000 for his owner. Photo courtesy Casey Sunsdahl.

The key is early diagnosis and treatment as soon as possible. Ireland said the most recent Minnesota data shows about 22% of dogs diagnosed with blasto either die from the disease or are euthanized because it has already impacted the dog’s internal organs, or because the owner can't afford the medicine to keep treating it for months as is usually required.

Blastomycosis is caused by inhaling spores from infected soil and it impacts the victim's lungs and ability to breathe properly. In advanced cases dogs may also develop sores on their skin or eyes. It can eventually spread to bones and joints and internal organs.

If diagnosed and treated early, the success rate is good. But even with medication if often takes months for the dog to recover. Of the dogs that contract blasto, about 78% will survive if they receive an expensive regime, often $1,000 or more per dog, of the antifungal medicine Itraconazole, the same antifungal medicine people take for blasto.

Hunting dogs at high risk

The disease impacts hunting dogs more than others, apparently because they spend more time off-leash outdoors and more time with their noses to the ground. Sled dogs, which often live on the ground in the woods, also are hard hit.

Often, the fungus can be picked up quickly while the owner and dog are at their cabin, on vacation with the dog or on a hunting trip in blasto hot spots, in addition to their home area. It can take from one to three months from the time of exposure to contaminated soils until the time symptoms appear.

Cases have been reported in all 87 counties in recent decades. But Cass, Aitkin, Itasca and especially St. Louis counties — the so-called blasto belt — are by far the most common areas where blasto infections occur, both in people and dogs. (In 1999, 18 people in Mountain Iron were diagnosed with blastomycosis — one person died — the largest human outbreak ever recorded in the state.) There continues to be a hot spot for outbreaks in the Tower-Ely area, across the Iron Range, around Duluth, the Grand Rapids area and in Cass County, where the Walker Animal Hospital has had a major run of blasto this summer.

Northern Minnesota isn't the only blasto belt. The Centers for Disease Control and Prevention says northern Wisconsin has the highest number of blasto reports nationally. Northwestern Ontario, especially near Lake of the Woods, also is a hot spot for blasto reports.

And while both people and dogs can contract the disease from the same site, four times more dogs have become infected as people this year.

Blastomycosis usually presents in dogs with a cough, loss of appetite, weight loss and lack of energy. But it also may include skin sores - like those shown here - joint and organ failure and other conditions. Contributed photo.
Blastomycosis usually presents in dogs with a cough, loss of appetite, weight loss and lack of energy. But it also may include skin sores - like those shown here - joint and organ failure and other conditions. Contributed photo.

“We really don't know if dogs are (physiologically) more susceptible to it, and that’s why we see more cases in dogs than people, or because it’s because they are so much closer to the soil than we are,’’ Ireland said. “We also don’t know if the big hunting dogs are more susceptible, or if it’s because there are so many of them; because they are so popular … or if those dogs are just getting more exposure.”

More than half of all cases occur in big, retriever-sized dogs over 50 pounds. About 25% of cases are in medium-sized dogs and 25% in small dogs. Three cats have been reported with blasto this summer. Historically, about 4% of all Minnesota animal cases of blasto are in cats, including some cats that never go outdoors. There have been just two confirmed cases in horses over the past 20 years, 1 in a rabbit and 1 in a tiger at the Lake Superior Zoo in Duluth (that happened after a flood disturbed soils at the zoo.)

“Obviously, if indoor cats are getting it, the spores are somehow getting into the house, either on someone’s shoe or in the air,” Ireland said.

Avoid freshly disturbed soils

It’s clear that dogs exposed to recently disturbed soils in blasto hot pots are more at risk, such as where a septic tank or basement is being dug or other construction is underway. Duluth veterinarian Tom Dougherty said one of his patient's dogs appeared to have been exposed to the spores when a truck used to haul dirt was cleaned out with an air hose near the dog’s kennel, spreading airborne spores. In another case, Dougherty said the spores apparently arrived when a wood pile with old firewood was relocated near the dog. In that case, the owner also became infected.

Casey Sunsdahl of Soudan, in the Lake Vermilion blasto hot spot, said he believes his Labrador retriever, Drake, contracted blasto a few years ago when a new sewer line was dug at his home. The dog was diagnosed with a serious case that required nearly 18 months of treatment. Drake fully recovered, but it was an expensive ordeal in addition to a lot of lost hunting time.

“It was pretty close to $400 a month, for the medicine and the urine tests we had to do, and it took about 18 months until the dog was completely clear of it,’’ Sunsdahl said. “I think it was about $5,000 by the time it was all over.”

Veterinarian Chip Hanson, owner of Ely Veterinary Clinic, by far the busiest blasto clinic in the nation, averaging roughly 40 cases annually, said he has found few reliable patterns in blasto breakouts. Some years are wet, some are not. Locations can look like critical blasto hot spots one year then stop producing cases the next.

“It’s a very mysterious disease. … No one knows what makes this thing spore-out on occasion and start impacting people and dogs when it’s been there all along doing nothing,” Hanson said.

“I had one sled dog operator who had 25 cases … within a year or two,” Hanson said. “The health department basically told him to move his family. But he stuck it out and (blasto) eventually calmed down, and he was down to no cases, or maybe one case per year. And no one really knows why.”

Hanson said the average dog must be treated for about six months until tests show they are completely free of the fungus. Most start improving after two weeks on the medicine. Dogs that don’t respond by then generally perish or are euthanized.

“For a few years we had people in our area … going up to Canada to buy cheaper pills in something that was probably quasi-legal,’’ Hanson said, noting the medicine has come down in price in the U.S. in recent years. Six months of Itraconazol is now about $1,000 for the medicine, Hanson noted, not including testing and vet fees.

Despite the risk, Ireland said people shouldn’t stay inside with their dogs out of fear.

“It’s not inevitable that a person or dog visiting an endemic area will get an infection. Overall, it’s still a rare disease, so the vast majority of people or dogs living or visiting these areas will not get sick,” she noted. “Being aware of the risk, and what to look for, is the best prevention we have right now.”

Pet owners can get blasto, too

Earlier in September, the News Tribune ran a front-page story about the big increase in blastomycosis cases in people this summer in Minnesota. Pet owners are reminded that they, too, can contract the disease from the same places dogs do. (It’s not contagious. It can’t be transmitted between dogs and humans or vice versa.) As of last week there had been 56 reported human cases in 2019 in the state, up from 31 in 2018. About 10 percent of humans diagnosed with blastomycosis die.

The fungus has an incubation period of about 45 days in people and since people are most likely to be around the soil during the summer, the number of reported cases tends to rise in September.

Blasto is not caused by bacteria, so antibiotics don't work. Blastomycosis often is discovered in people when a biopsy of a spot in a patient's lung is sent to a cancer pathologist who finds the fungus instead of cancer, experts say. Once the disease is diagnosed, antifungal treatments are available. In severe cases, the patient may have to be treated through an IV in the hospital. In many cases, the patient can take a pill, although they'll have to keep doing so for six to 12 months.