Outbreak of human trichinellosis in Northern California caused by Trichinella murrelli

Abstract

In October of 2008, an outbreak of trichinellosis occurred in northern California that sickened 30 of 38 attendees of an event at which meat from a black bear was served. Morphologic and molecular testing of muscle from the leftover portion of bear meat revealed that the bear was infected with Trichinella murrelli, a sylvatic species of Trichinella found in temperate North America. Clinical records revealed a high attack rate for this outbreak: 78% for persons consuming any bear meat and 100% for persons consuming raw or undercooked bear meat. To our knowledge, this report is the first published report of a human trichinellosis outbreak in the United States attributed to T. murrelli, and it is the second such outbreak reported worldwide.

Figure 1.

Cases of trichinellosis (N = 29) associated with consumption of bear meat in Humboldt County, California in 2008.

Figure 2.

Change in Trichinella spp. antibody levels observed in ill persons submitting acute- and convalescent-phase serum in Humboldt County, California, 2007–2008.

Figure 3.

Trichinella larva encysted in muscle tissue from bear paw.