Family suffers from rare brain worms after eating undercooked bear

In the summer of 2022, a family gathered in South Dakota for a reunion that included a special meal: skewers made from black bear meat that one of the family members had “harvested” in the northern Saskatchewan, Canada, in May. Lacking a meat thermometer, the family assessed the doneness of the dark-colored meat by eye. At first, they accidentally served it rare, which a few family members noticed before the decision was made to recook it. The rest of the reunion was unremarkable and family members left for their homes in Arizona, Minnesota and South Dakota.

But a few days later, family members started getting sick. One, a 29-year-old Minnesota man, sought care for a mysterious illness characterized by fever, severe muscle pain, swelling around the eyes (periorbital edema), high blood cell counts whites fight infections (eosinophilia, a common reaction). parasites) and other laboratory abnormalities. The man sought treatment four times and was hospitalized twice in 17 days in July. It wasn’t until his second hospitalization that doctors discovered the bear meat – and then everything made sense.

Doctors suspected the man of suffering from a disease called trichinellosis and an infection of the Trichinella nematodes (roundworms). These dangerous parasites can be found worldwide, embedded in the muscle fibers of various carnivores and omnivores, according to the Centers for Disease Control and Prevention. But it is quite rare to find them in humans in North America. Between 2016 and 2022, there have been seven outbreaks of trichinellosis in the United States, involving only 35 cases. The majority of these were linked to the consumption of bear meat, but moose and wild boar meat are also common sources.

Enlarge / Microscopic examination of larvae encapsulated in a direct preparation of muscle gourd made from black bear meat (A), larvae released from artificially digested bear meat (B), and motile larvae observed by interference contrast microscopy differential (C and D)* from black bear meat suspected of being the source of an epidemic of human diseases Trichinella native infections – Arizona, Minnesota and South Dakota, 2022.

Once eaten, the larvae encased in the meat are released and begin to invade the small intestine (the gastrointestinal phase), causing pain, diarrhea, nausea and vomiting. Then the larvae develop into adults in the intestine, mate and produce other larvae there. The second generation of worms then travels through the lymphatic system, into the blood, and then throughout the body (systemic phase). The larvae can be found everywhere, reaching skeletal muscles, the heart and the oxygen-rich brain. The systemic phase is marked by fever, periorbital edema, muscle pain, cardiac inflammation, and brain inflammation. The larvae can also cause severe eosinophilia, particularly when they enter the heart and central nervous system.

The man’s symptoms matched the case and several tests confirmed the parasitic infection. Of the eight interviewed family members present at the bear meat meal, six people suffered from illnesses comparable to trichinellosis (aged 12 to 62) and three of them were hospitalized, including the 12-year-old child. years. Four of the six sick people had eaten bear meat, while two had only eaten vegetables cooked with the meat and cross-contaminated. CDC experts obtained frozen samples of bear meat, which revealed moving larvae. Tests identified the worm as Native Trichinellaa frost-resistant species.

In a study of the outbreak published Thursday in the CDC’s Morbidity and Mortality Weekly Report, Minnesota health officials and the CDC reported that the three hospitalized patients had been treated with the antiparasitic drug albendazole , and had recovered. The remaining three cases fortunately recovered without treatment. Health experts have noted how difficult it can be to identify and diagnose these rare cases, but have pointed to periorbital edema and eosinophilia as key clinical clues to grizzly bear infections. Most importantly, people who are going to eat wild game meat should invest in a meat thermometer and ensure that the meat is cooked to at least ≥165°F (≥74°C) to avoid risking game worms. brain.