Trichinellosis (trichinosis) is a parasitic infection caused by nematodes (roundworms) of the genus Trichinella. Pigs are the most important source of human infection, although a number of other animals are also epidemiologically important hosts. Consumption of raw or undercooked meat is the principal mode of transmission.
Trichinellosis has been reported worldwide. The prevalence of human infection is highest in China, Thailand, Mexico, Argentina, Bolivia, the former Soviet Union, Romania, and other parts of Central Europe .
There are 8 species and 11 genotypes of Trichinella; these are divided into those that encapsulate in host muscle tissue of mammals only, and those that do not encapsulate and infect mammals, birds (one species), or reptiles (two species). All recognized species and genotypes can infect humans, but there are seven species of Trichinella that have been implicated in human disease [2,3]:
- T. spiralis is found worldwide in a great variety of carnivorous and omnivorous animals.
- T. nativa is found in arctic regions and infects bears, foxes, and walruses.
- T. nelsoni is present in Africa, south of the Sahara, where it is common in felid predators and scavenger animals, such as hyenas and bush pigs.
- T. britovi is found in temperate areas of Europe, western Asia, and western/southern Africa in carnivores but not domestic swine.
- T. pseudospiralis is found in mammals and birds worldwide [4,5].
- T. murelli is found in wild mammals in the United States and Japan .
- T. papuae is found in Papua New Guinea in domestic and feral pigs . It has also been reported from Thailand [8,9] and Taiwan .
One additional species, T. zimbabwensis, has been described in crocodiles in Tanzania . The clinical importance of the additional known genotypes of Trichinella is not known . Information on species and genotype distribution and host range can be downloaded from the International Trichinella Reference Centre .