Parasitic Organisms

Although long-recognized as an important public-health problem, foodborne diseases are receiving an increasingly greater share of the public's attention. The Centers for Disease Control estimates that 6.5-33 million Americans (314% of the population) contract a foodborne infection annually, with more than 9,000 associated fatalities. Foodborne pathogens also constitute a major cause of morbidity and mortality worldwide. The World Health Organization estimates that more than 1 billion cases of acute diarrhea occur annually in children 1-5 years of age in the developing countries. The most important microorganisms and parasites transmitted by food, particularly meat, are listed in Table 1. In the United States, concern over protozoan and helminth parasites lies mainly with Toxoplasma gondii (toxoplasmosis), Sarcocystis spp. (sarcocys-tosis), Trichinella spiralis (trichnellosis), larval and adult

Table 1. Foodborne Disease Agents


Hepatitis A virus

Norwalk agent

Other Norwalklike viruses



Astro viruses"


Snow-mountain agent

Cockle agent

Coxsackie B viruses

Calicivi ruses"


Salmonella spp. Shigella spp. Campylobacter spp. Escherichia coli Vibrio parahaemolyticus Listeria monocytogenes Yersinia spp.


Anaskis spp. Eustrongylides spp. Pseudoterranova spp. Trichinella spiralis Angiostrongylus spp. Paragonimus spp. Diphyllobothrium latum Taenia spp. (Cysticercus)








"Viruses that cause gastroenteritis and that may be foodborne.

infections of Taenia saginata and Taenia solium (taeniasis and cysticercosis), and the fishborne nematodes (eg, ana-sakiasis). The importance of these parasites relates not only to their direct clinical effect, but also to the high economic costs associated with prevention of their entrance into the domestic food chain and with medical care. Estimated annual costs for inspection and condemnation at animal slaughter are shown in Table 2. Note that losses for fascioliasis and ascariasis represent condemnations for reasons that are more esthetic than public health ones.

All these losses have an important indirect consequence, namely lowering consumer confidence in meat safety and quality. Although reliable figures are difficult to obtain, some economists and public-health workers believe that the cost of foodborne parasites, in terms of public-health expenditures and lost wages, is very high. Estimated annual costs for human taeniasis (from bovine cys-ticerocosis) is $100,000; for trichinosis, $1.5-2.2 million; and for congenital toxoplasmosis, up to $215—323 million in terms of medical care and work loss (1).

Consumer attitudes, even in the absence of firm facts, can also have a severe economic impact on an industry. A good example of this is trichinellosis. It is thought that public awareness that pork might be infected with Trichinella spiralis costs pork producers several hundred million dollars annually in suppressed consumer demand and loss in exports (2). This despite the fact that less than one hog per 1,000 might be infected and only about 50 to 100 human infections are diagnosed each year in the United States. Obviously, the potential consequences of increased public concern over pork-transmitted Toxoplasma gondii will also be economically important. It should be noted that firm facts on the role of meat in human toxoplasmosis are still lacking, and research is underway to clarify the question of the importance of pork vis a vis cat feces in transmission to humans. All this underscores the fact that producers have much at stake in controlling and, in some cases, eradicating foodborne parasites, regardless of their direct role in animal and human health.

The rising public concern over food safety presents new and difficult challenges for the research community. Many current procedures and strategies for ensuring a healthful and safe meat supply will require marked improvement in order to meet expected demands; this is especially true for foodborne parasites (3). For the three most serious meat-

Table 2. Estimated Losses Due to Slaughterhouse Condemnations


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