Food-Borne Parasites

Food-borne infections are a significant cause of morbidity and mortality worldwide, and food-borne parasitic diseases, though not as widespread as bacterial and viral infections, are common on all continents and in most ecosystems, including arctic, temperate, and tropical regions. Major food-borne trematodiasis in humans has been discussed in this chapter. Taenia saginata, the beef tapeworm, and T. asiatica and T. solium, the pork tapeworms, cause taeniasis in humans. Taenia saginata and T. solium occur worldwide, endemically in underdeveloped regions where pork and beef are consumed and sporadically in developed nations, largely due to importation by immigrants and travelers. The neck of the tapeworm begins the process of strobilation, the production of proglottids. Humans and other piscivorous mammalian hosts harbor the adult tapeworm, which is attached to the small intestinal surface by the scoop-shaped scolex and bothria (or grooves), which are characteristic holdfast organs of pseudophyllidean tapeworms. Adult tapeworms are generally benign, but abdominal pain, nausea, and diarrhea may occur, and Diphyllobothrium latum may absorb enough vitamin B12 to cause deficiency in malnourished individuals. Nematodes in the genus Trichinella are some of the most commonly recognized agents of food-borne parasitic disease. Gnathostomes are species belonging to a geographically widespread genus but are most commonly found as adult worms in carnivorous mammals in Asia. The most widespread protozoan parasite affecting humans is Toxoplasma gondii. To prevent food-borne infection by T. gondii, the hands of people handling meat should be washed thoroughly with soap and water before they go to other tasks.