Nematodes of this genus are distributed worldwide and infect various mammals. The cause of trichinellosis had been believed to be
Trichinella spiralis. However, it is now recognized that the cause consists of at least 8 species in this genus. Adult worms infect the intestine of the host. The larvae released from the adults migrate to muscle tissues and wait for the host to be eaten by predators. Therefore, the same host species can act as both the definitive and intermediate hosts.
The infection causes fever, edema and muscle pain in humans, and in severe cases, it may be fatal because of cardiac arrest or respiratory paralysis. In Japan, it was reported that human infections were associated with the ingestion of raw bear meat. Heating of raw meat is necessary to kill the larvae since they can live in frozen meat kept at −18 C for five years.
