CONSIDERATION OF POTENTIAL PARASITE FOOD HAZARDS’ Helen E. Jordan, D.V.M., Ph.D.2 Health authorities sometimes underestimate the potential threat of parasitic infections in places where good health conditions prevail. Though current infection rates may be near the vanishing point, many parasite species not listed in official reports are often present in small numbers, so that a drop in public health standards could prompt a rapid rise in these rates of infection. Introduction the many food sources involved and the condi- tions under which such meals are prepared, The extensive international trade and human distributed, and maintained. travel of our jet age means that both human It is also necessary to keep in mind the many and animal disease problems in developing ways parasites can be transmitted to food. For countries can have profound effects upon more example, there is an increasing potential for industrialized and urbanized populations. food contamination by solid wastes (feces) in Therefore, in order to deal with parasite food some parts of the world. In general, infective hazards in relatively developed countries, such stages of parasites in feces can come in contact as the United States of America, international with food when feces are used as fertilizer or as well as national and local food safety must when an infected food processor-who may be be considered. For example, meals served anyone from a field worker to a food handler, aboard international airliners should be re- cook, waiter, or housewife-does not practice garded as a potential health hazard because of good hygiene. Tables 1-3 show many of the parasites which ‘Presented to the Symposium on Parasites in Relation to Man’s Health, American Society of Parasi- man can acquire from contaminated food. tologists, Los Angeles,California, August 1971. Table 1 includes those parasites which use an 2Departmentof Veterinary Parasitologyand Public Health, College of Veterinary Medicine, Oklahoma animal consumed by man as an intermediate State University, Stillwater, Oklahoma. host. They are listed in either column one or TABLE l-Genera of human parasites using an animal eaten by man as an intermediate host. Parasites with terrestrial Parasites with aquatic intermediate intermediate hosts hosts Protozoa: *Toxoplasma Trematodes: *Paragon&us, *Heterophyes, Metagonimus, *Phagicola, Cestodes: *Taenia saginata and Clonorchis, Opisthorchis. Taenia solium Nanophyetus, *Dicrocoelium, Echinochasmus, *Echinostoma, Nematodes: *Trichinella Echinoparyphium, Himasthla, Paryphostomum, Plagiorchis. Arthropods: Linguatula and Isoparorchis Cestodes: *Diphyllobothrium, *Spirometra, Diplogonoporus Digramma, Ligula, and *Mesocestoides Nematodes: Angiostrongylus, Anisakis, and Dioctophyma *Reported in the United States. 143 144 PAHO BULLETIN . Vol. VIII, No. 2, 19 74 4 I TABLE Z-Genera of human parasites whose infective stages are transmitted in fomite or by invertebrate vectors. Transmitted in Transmitted by invertebrate fomite vectors Protozoa: *Isospora Cestodes: *Dipylidium, *Hymenolepis, t *Bertiella, Raillietina Y Nematodes: *Enterobius and Digramma Nematodes: *Gnathostoma, *Gongylonema, Physaloptera, Spirocerca, and Metastrongylus *Reported in the United States. column two, depending on whether the inter- drinking water contaminated with sewage (11, mediate host is terrestrial or aquatic. 15, 21, 31, 38, 41). Table 2 includes those parasites which may be airborne on a fomite,3 or which may be Specific Examples of Parasite Transmission c transmitted by some intermediate invertebrate host that accidentally falls or crawls into food. To illustrate these general transmission path- 4 Table 3 lists parasites contained in excreta ways, several specific examples have been se- which may reach human food by way of lected. sewage, polluted water, or fertilizer. Either irrigation or flooding can lead to food contami- Taenia nation from polluted water; and in view of increasing pollution and recycling activities, this Taenia saginata, the beef tapeworm, provides P poses a definite potential danger of contamina- a good example of the pathways employed by a tion involving vegetable and other field crops human parasite that uses a common food r (4 g-11,2.5, 29, 35, 37-38, 41). animal as an intermediate host. The life-cycle of Taenia, shown in Figure 1, is self-explanatory. Another important way in which excreta- , borne parasitic infections can be spread is in Anisakis ‘c 3Fomite =Any substance other than food that may harbor and transmit infectious organisms. Many parasites normally occurring in wild TABLE 3-Genera of human parasites whose infective stages are transmitted in sewage or polluted water. Protozoa: *Entamoeba, Endolimax, Nematodes: *Strongyloides, f Isospora, lodamoeba, * Triehuris, Vapillaria, Dientamoeba, *Toxoplasma, *Ancylostoma, Necator, . *Giardia, *Trichomonas Haemonchus, Oesophagostomum, Ternideus, *Trichostrongylus, Trematodes: Schistosoma, Fasciola, Syngamus, “Syphacia, Fasciolopsis, Watsonius, *Ascaris, *Toxocara, Gastrodiscokies * Toxascaris, Lagochilascaris. A Dracunculus, Acanthocephala: Cestodes: *Cysticercus (larva of Macracanthorhynchus, 4 Taenkz), *Hydatid (larva of Moniliformis Echinococcus), Voenurus (larva of Multiceps). Arthropods: Porocephalus Drepanidotaenia *Reported in the United States. Jordan . POTENTIAL PARASITE FOOD HAZARDS 145 FIGURE l-Transmission pathways of the beef FIGURE 3-Postulated transmission pathways of tapeworm, Taenia saginata. Spirocerca tupi. The known life-cycle of S. tupi suggests that a definitive host, such as the dog, passes lN6ESllON eggs via its excreta to one of several coprophageous (dung-feeding) beetles. Infected beetles may either get into food eaten by man or they may infect a paratenic host (the chicken). In the latter case, S. tupi larvae encysted in the chicken’s alimentary tract may then infect man. INGESTION and domesticated animals can infect man when given the opportunity. One example of this is Anisakis, a nematode parasite whose adult form is normally found in marine mammals (27, 28). The intermediate host of Anisakis is a fish, and Entamoeba histolytica man acquires the infection by ingesting raw infected fish (see Figure 2). A good example of a parasite whose infec- tive stage is found in both animal excreta and polluted water is Entamoeba histolytica. Figure Spirocerca lupi 4 shows several of the known ways in which the Entamoeba cyst may reach and contaminate Another example of an animal parasite human food. occurring abnormally in man is the nematode Spirocerca lupi, which provides an illustration Parasites in Economically Developed Regions of parasitism involving an insect vector. Figure 3 shows possible ways in which man may Chandler (16) has stated that “Improved acquire this parasite. water supplies and good sewage disposal are FIGURE 2-Transmission pathways of Anisatcis. DEFINITIVE HOST [MARINE MAMMAL] CONTAMINATED 146 PAHO BULLETIN . Vol. VIII, No. 2, 1974 FIGURE 4-Some of the known transmission pathways of Enramoeba hisrolyrica. IRRIGATION, SOLID WASTES [FECES] dangerous to most intestinal infections. To the owing to better opportunity for improved extent that these concomitants of civilization water, control of foods, and sanitary sewage have become part of the way of life of a people, disposal.” However, due to the increasing world parasitic infections have decreased even without population and the recycling of waste products, new insecticides, new chemotherapeutics, or including sewage, the benefits of civilization new vaccines. These specifically developed that Chandler so eloquently described may not weapons have practically completed the white be assured. I propose that one of the greatest man’s freedom from most of the infectious potential hazards to highly industrialized na- diseasesthat he once justifiably feared. tions is a false sense of security. “For our domestic animals, on the other In the United States the same parasitisms hand, domestication and increasing concentra- exist, though admittedly to a lesser degree, that tion have meant increasing parasitization, for existed 30 or 40 years ago. For example, the they soil their table with their feces, they eat parasites reported from two states for the years uncooked food, they drink contaminated 1969 and 1970 are shown in Table 41 waters from ponds and streams, they bathe As may be seen, in the southern state only only by accident. _ For human parasites, 10 Entamoeba cases were reported for 1969 increased concentration had an opposite effect while 24 were reported for 1970. Other intesti- Jordan . POTENTIAL PARASITE FOOD HAZARDS 147 TABLE $-Comparison of two states’ annual reports of possible food-borne parasites. Southern state Southwestern state Types of infections 1969 1970 1969 1970 Protozoan infections with: 10 24 49 54 (1) Entamoeba (2) Intestinal protozoa (mainly Giardia) - 342 - - Helminthic infection with: (1) Ancylostom 280 303 - - (2) Ascaris 403 199 - - (3) Enterobius - 163 - - (4) Strongyloides 16 20 - - (5) Trichinella 4 1 0 0 (6) Trichuris - 80 - - nal protozoa were reported for the first time in down in public hygiene or in sanitary disposal 1970. When personnel of the state public health of human and animal excreta occurs, contami- department were asked to interpret the situa- nation of food with the infective stages of such tion and to name the genera of parasites parasites could follow. If this unsanitary condi- involved, they said that the caseswere predomi- tion were to go undetected, the affected food nantly Giardia infections