What Is Blastomycosis? Fungal Infection Sickens 4 People, 5 Dogs In Wisconsin

Health authorities have reported a cluster of Blastomyces infections in Wisconsin that affected both humans and dogs. One person died after getting infected.

A veterinarian in St. Croix County alerted authorities in February last year that four dogs were diagnosed with blastomycosis, the U.S. Centers for Disease Control and Prevention (CDC) said in a report. The dogs were all living within a one-mile area, and two people also fell ill from "the same area within 3 weeks of the canine cases."

Four humans and five dogs were diagnosed with blastomycosis from January to March 2022. The five dogs reportedly had mild cases though one had a "subcutaneous mass that contained Blastomyces yeast."

The four people experienced symptoms such as coughing and shortness of breath. Two of them had severe symptoms and had to be hospitalized. One of them died.

"Before January 2022, no blastomycosis cases had been reported in residents of this neighborhood during the preceding 10 years, although one dog reportedly died of blastomycosis during the previous year," the CDC noted.

It's possible that construction activities in the neighborhood in the last decade have helped disperse the Blastomyces spores, the agency said, while stressing the need for a "more comprehensive" investigation.

"Although blastomycosis is infrequently reported, clusters have occurred primarily among persons engaging in recreational activities along waterways or in areas with ongoing excavation," it added.

What Is blastomycosis?

Blastomycosis is a fungal infection in humans and animals that's caused by inhaling the spores of the fungus Blastomyces dermatitidis. It may present as a pulmonary infection, with symptoms like dry, hacking cough, chest pain, fever, chills and drenching sweats. Symptoms of an extrapulmonary infection may depend on the affected organ, with skin lesions being the "most common side of dissemination."

In some cases, it may also be asymptomatic, thus making it unrecognizable. It resolves on its own sometimes, though it can also lead to "severe, and occasionally fatal, disease without antifungal treatment."

Blastomyces dermatitidis is endemic in some parts of the U.S., including Ohio, the Great Lakes region, upstate New York, the Mississippi River valleys and the Southeastern U.S. It is also endemic in Wisconsin, which reportedly has the highest incidence of the Blastomyces infection in the country, according to the CDC.

While other deep fungal infections occur mainly in immunocompromised hosts, blatomycosis can also happen in immunocompetent hosts.

"The prognosis of patients who are immunocompetent is generally good as they have a decreased chance of suffering from complications of the infection," noted the National Institutes of Health. "Successful treatment of this condition is achieved in approximately 80% to 95% of cases."

The prognosis may be poorer in immunocompromised patients.