Current status of food-borne parasitic zoonoses in the United States.

Although not a major public health problem, food-borne parasitic zoonoses in the United States are the cause of numerous diseases that occur widely in the population. The most common food-borne parasitic diseases in the United States are trichinosis, toxoplasmosis, taeniasis/cysticercosis, diphyllobothriasis, and anisakiasis. Since 1947, when the US Public Health Service began to record statistics on trichinosis cases in humans, the numbers of reported cases in the United States have declined markedly, from an average of about 400 with 10-15 deaths reported each year in the late 1940s, to an average of 57 per year with three deaths overall in the 5 years 1982-1986. Each year throughout the world, Toxoplasma gondii infects millions of persons, who contract it either by eating raw or poorly cooked meat from infected animals such as hogs or sheep or by ingesting soil contaminated with cat feces. In the United States between 400 and 10,000 infants are born each year with congenital toxoplasmosis. Toxoplasmic encephalitis, marked by dementia and seizures, has become the most commonly recognized cause of central nervous system opportunistic infection in AIDS patients. Intestinal taeniid tapeworm infection acquired in the United States is almost entirely caused by Taenia saginata, the beef tapeworm. Neurocysticercosis, caused by larvae of the pork tapeworm Taenia solium, is diagnosed in hundreds of persons in the United States every year. Nearly all patients are immigrants or travelers from Mexico and other disease-endemic areas. Diphyllobothriasis and anisakiasis both have increased in recent years in association with increasing popularity of raw fish dishes. Adequate prevention and control of food-borne parasitic zoonoses require continued and improved programs to educate consumers, producers and medical practitioners.