A 2023 outbreak of trichinellosis tied to undercooked bear meat in western North Carolina points to the need for local health departments and wildlife managers to educate people about safe wild-game meat preparation, say investigators from the Centers for Disease Control and Prevention (CDC) and the North Carolina Department of Health and Human Services.
In a report published yesterday in Morbidity and Mortality Weekly Report (MMWR), the authors described the outbreak, increasing proportions of which are linked to wild-game consumption. Trichinellosis, also called trichinosis, is caused by Trichinella worms from the consumption of raw or undercooked meat containing dormant larvae.
The rare parasitic disease usually causes muscle pain and fever (54% of cases) and facial swelling (42%) and can lead to persistent muscle pain and, rarely, death (0.2%).
Diagnosis challenging, treatment expensive
The index patient, who had flu-like signs and symptoms and facial swelling, was reported to the North Carolina Division of Public Health on November 29, 2023.
Cooking wild game meat to an internal temperature ≥165°F (≥74°C) is necessary to kill Trichinella spp. parasites.
Among 34 surveyed attendees of the gathering, 22 said they ate undercooked bear meat, with 10 having signs and symptoms of trichinellosis. Nine of the 10 case-patients had facial swelling, six had muscle pain, and four had fever. Patients ranged in age from 10 to 40 years (median, 17 years). The median incubation period (time from ingestion to symptom onset) was 21 days (range, 7 to 26 days). Most patients were prescribed an antiparasitic drug, but in some cases, use of the drug was delayed.
Five patients were tested for Trichinella immunoglobulin G antibodies. While all results were negative, confirmatory diagnosis requires additional convalescent-serum testing, for which none of the patients returned. No bear meat was available for testing.
"Moreover, whether the patient was treated or not, confirming infection through testing of convalescent serum is challenging because acute symptoms have often resolved by the time samples can be collected," the researchers wrote. "Recovered patients might have little incentive to return for testing."
Although trichinellosis remains rare, the researchers noted that hunters kill thousands of bears each year in North Carolina, and black bears are common hosts for Trichinella species.
"Communication of safe wild game meat preparation is the most effective way to prevent trichinellosis," the authors wrote. "Diagnostic antibody tests might have poor accuracy, and treatment costs can be substantial. Cooking wild game meat to an internal temperature ≥165°F (≥74°C) is necessary to kill Trichinella spp. parasites."
