Family members infected with brain worms after eating undercooked bear meat

A number of family members who shared a meal of bear meat that one of the family members had harvested earlier were subsequently infected with brain worms, according to a new report from the Centers for Disease Control and Prevention.

In July 2022, the Minnesota Department of Health was flagged that a 29-year-old man had been hospitalized multiple times over a two-and-a-half-week period with symptoms including fever, severe muscle soreness, swelling around the eyes, and other various maladies.

Following his second hospitalization, the man told doctors that he had days earlier attended a family gathering in South Dakota, and that one of the meals they shared included kabobs made from black bear meat that "had been harvested by one of the family members in northern Saskatchewan."

The meat had been in a freezer for a month and a half before being thawed out for the meal. The CDC reported that, because the meat was darker in color, it was initially and inadvertently served rare. Family members began eating the kabobs but noted that the meat tasted underdone, so it was recooked and served again.

Nine family members, largely from Minnesota but also hailing from South Dakota and Arizona, ate the meal, though some of them only ate the vegetables, which had been cooked and served alongside the bear meat.

Doctors ultimately diagnosed the 29-year-old man with trichinellosis, a roundworm which is rare in humans and usually acquired through the consumption of wild game. Once in a human host, the larvae can then move through the body to muscle tissue and organs, including the brain.

Five other family members were diagnosed with these freeze-resistant worms, including a 12-year-old girl and two other family members who had only eaten the vegetables at the meal. In all, three family members were hospitalized, and were treated with albendazole, which the Mayo Clinic says keeps the worms from absorbing sugar "so that the worm loses energy and dies."

The CDC advised that the only sure way to kill trichinella parasites is to adequately cook the meat it resides in, to an internal temperature of at least 165 degrees F, and reiterated their warning that it can cross-contaminate other foods.

The CDC said estimates of how prevalent trichinella parasites are among wild animals range widely, but it's thought that up to one-quarter of black bears in Canada and Alaska may be infected.

Brain worms made national news earlier this year, after presidential hopeful Robert F. Kennedy Jr. disclosed that a parasitic worm he contracted years ago "ate a portion" of his brain, causing potential cognitive issues.

Symptoms of brain worm infection can include nausea, vomiting, headaches and seizures, Dr. Céline Gounder told "CBS Mornings." However, some people who contract the worms may also see no symptoms at all. Gounder added usually these parasites get "walled off by your immune system and they get calcified."

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Eric Henderson

Eric Henderson is Managing Editor, Midwest for CBSNews.com. He has won three Emmy Awards, an Eric Sevareid Award and two Edward R. Murrow Awards.