The present status of trichinellosis in Thailand.

The epidemiology of trichinellosis in northern Thailand may be unique. Since 1962, outbreaks of the disease have occurred almost every year. The Department of Communicable Disease Control, Ministry of Public Health reported 118 discrete outbreaks of the disease, involving 5,400 patients, 95 of whom have died. Epidemiological investigations reveal that the outbreaks have occurred mostly in rural areas, associated with villagers celebrating local and traditional festivals such as the northern Thai New Year, wedding ceremonies, or other festive occasions. In almost all cases the source of infection has been traced to either hilltribe pigs, which are raised like wild animals, or to meat from wild boar. Infection is usually acquired through consumption of a local dish called "lahb," traditionally served during these festivities. This popular dish consists of raw finely chopped meat mixed with spices and chilies and is served nearly raw. Common clinical symptoms of trichinellosis in northern Thailand are fever and myalgia, presenting about two weeks after ingestion of raw meat containing encysted Trichinella larvae. Based on its infectivity for rats and pigs and on alloenzyme typing, the species appears to be Trichinella spiralis. The transmission cycle of trichinellosis in northern Thailand is primarily of a sylvatic type. Hilltribe pigs, wild boars, black bear and jackal are common reservoirs. Man intrudes into the cycle by eating the raw or under-cooked meat of these animals.