Parasites and the Food Supply

1990). Today, that figure has multiplied by more than a factor of 8. In the past, the risk of human infection with parasites was considered to be limited to distinct geographic regions because of parasites’ adaptations to specific definitive hosts, select intermediate hosts and particular environmental conditions. These barriers are slowly being breeched—first by international travel developing into a major industry, and then by rapid, refrigerated food transport which became available to an unprecedented degree at the end of the 20th century. Figs. 2A and B trace the numbers of international travelers to and from the U.S. over the past decade and provide further projections for international travel through 2003. International travel and population migration are the primary mechanisms by which immunologically naive (previously unexposed) consumers may come into contact with emerging parasites. Another factor to consider is the rapid transport of foreign food products to the U.S., which has further enhanced the chances that parasites come into contact with consumers. Now, produce picked and seafood harvested or caught early in the week, thousands of miles from our borders, can be consumed fresh in America’s heartlands before the weekend. Moreover, cultural habits have shifted toward the consumption of fresh, i.e., raw and undercooked, foods that bypass important preparatory measures inParasites and the Food Supply