Six relatives got infected with brain worms after eating black bear meat one of the family members had harvested, according to the Centers for Disease Control and Prevention.

A group of nine extended family members gathered in May 2022 in South Dakota and ate grilled kabobs of vegetables and black bear meat, harvested by one of the family members in northern Saskatchewan, Canada in May 2022, the CDC says in a report published May 23 in the agency's Morbidity and Mortality Weekly Report.

After a few ate some of the meat, they noticed it was undercooked, so they cooked the meat some more, according to the report, written by CDC and state health officials.

Six days later, one of the family members, a 29-year-old man, was hospitalized with symptoms including fever, severe muscle aches and pains, swelling around the eyes, and eosinophils (high count of white blood cells that support the immune system).

During a second hospitalization, health care providers learned about the bear meat consumption and treated him with albendazole, which is used to treat trichinellosis, a disease caused by an infection of microscopic and parasitic roundworms.

The bear meat had been frozen and, while freezing kills many some Trichinella worms, others are freeze-resistant. When people ingest infected meat, larvae can evolve and produce more parasites.

Worms can make their way through the body to the heart and brain, which can lead to inflammation of the heart muscle and brain. There they can form cysts and potentially cause seizures.

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Six at family gathering infected with roundworms

Symptoms of trichinellosis can include stomach pain, diarrhea, nausea, and vomiting, the CDC says.

But some people who contract the worms may see no symptoms at all, infectious disease specialist Dr. Céline Gounder said recently in an interview with "CBS Mornings." Gounder added usually these parasites get "walled off by your immune system and they get calcified." CBS News first reported the CDC report.

After the Minnesota Department of Health began an investigation, researchers learned that the outbreak involved a total of six from the gathering who were infected – four who ate the meat and two who ate just vegetables. They ranged in age from 12 to 62 and resided in Minnesota, Arizona and South Dakota, according to the report.

Among those who were sickened, two more were hospitalized and also treated with albendazole, the CDC said.

How can eating bear meat lead to getting brain worms?

Black bears are likely carriers of roundworms. As many as 24% of black bears in Canada and Alaska may be infected, the CDC says. The bear meat in this case was tested and found to have Trichinella nativa, a freeze-resistant type of roundworm.

Still, reported cases of trichinellosis are rare, with the CDC logging only seven outbreaks from January 2016 to December 2022, with 35 probable and confirmed cases, the agency said. Bear meat was the confirmed or suspected source of infection in the majority of those outbreaks, the CDC said.

Bear meat should be cooked to an internal temperature of at least 165 degrees to kill the parasites. Since infected meat can cross-contaminate other foods, the raw meat should be kept and prepared separately, the agency said.

Brain worms have been in the news recently after a report in The New York Times that years ago doctors had found a dead worm in the brain of Independent presidential candidate Robert F. Kennedy Jr. 

Contributing: Emily DeLetter and Eric Lagatta.Follow Mike Snider on X and Threads: @mikesnider & mikegsnider.

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