often responsible for anisakiasis are cod, pollock, halibut, rockfish, flatfish, mackerel, salmon, and herring. Although only 50 cases were documented in the United States from 1958 to 1988 (McKerrow et al., 1988), these figures probably underestimate the actual incidence of anisakiasis, which is not a reportable disease. In countries in which the consumption of raw seafood is common, anisakiasis is more prevalent. In 1984 in Japan, for example, 3,141 cases were reported (Oshima, 1987). With the current U.S. trend to encourage more people to eat fish for dietary reasons, it is important that the consumer be reminded to thoroughly cook the fish to preclude infection with nematodes, such as those that cause anisakiasis.

Water Treatment

Water that is untreated or that does not receive adequate processing can transmit infectious agents, such as bacteria (Vibrio cholerae, Salmonella typhi, enterotoxigenic Escherichia coli), viruses (hepatitis A virus and other enteroviruses, rotaviruses, Norwalk gastroenteritis viruses), and protozoan parasites (Giardia lamblia, Cryptosporidium, Entamoeba histolytica). A primary source for many of these pathogens is fecal contamination of source water that is subsequently inadequately treated, or similar contamination after treatment. Leakage of wastewater from septic tanks and other sewage disposal facilities into groundwater can also transmit infection. Fortunately, most water used in this country is effectively processed by municipal water treatment facilities.

In some instances, water is not treated. This is often the case with water from private wells or from natural springs. In 1989, for example, an outbreak of some 900 cases of gastroenteritis occurred in a new resort community in north-central Arizona. An investigation revealed that the source of the outbreak was tap water obtained from a deep well on the resort property. A Norwalk-like virus was apparently introduced into the well by a faulty sewage treatment facility nearby, whose untreated sewage passed through fractures in the sandstone and limestone fields surrounding the well (Lawson et al., 1991).

Water used for recreational purposes can also be the source of waterborne infectious disease outbreaks, caused by pathogens such as hepatitis A virus (Bryan et al., 1974) or Shigella (Blostein, 1991). Particularly in the southwestern portion of the United States, water used for recreation increasingly is actually reclaimed wastewater. Wastewater treated to remove undesirable organic and inorganic contaminants is also being used for irrigation, industrial processing, and nonpotable residential (watering lawns and trees, toilet flushing) and commercial (golf courses, for example) applications. Inadvertent ingestion of reclaimed water, which has undergone the same basic treatment as potable water (including disinfection), is not likely



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