The life-cycle of T. solium has been understood since Kuchenmeister (1855) proved that the ingestion of cysts obtained from infected pork and mixed with food gave rise to adult tapeworms in the intestine in prisoners (Figure 23.7). Two years earlier, in 1853, Van Beneden had shown that the ingestion of T. solium proglottids caused cysticercosis in pigs. Rigorous meat inspection practices, the development of an increasing number of farms in which pigs are
reared under highly controlled conditions, and significant improvement in hygiene standards and sanitary installations in Europe and North America have contributed to the eradication of taeniasis and human cysticercosis in the majority of developed countries (Gemmel et al., 1983). Population mobility has, however, contributed to the appearance of an increasing number of cases of NC in the USA among Latin-American immigrants. In 1992, cases of autoctonous NC were reported in the Bronx, NY, which were probably transmitted by a Mexican domestic worker who was diagnosed with intestinal T. solium (Schantz et al, 1992). During the past 15 years a number of epidemiological studies have been carried out in Mexico, Guatemala, Honduras and Peru (Diaz-Camacho et al, 1991; Sarti et al, 1992; Allan et al, 1996; Sanchez et al 1997; Garcia et al., 1995) in order to obtain more precise information on the frequency and geographic distribution of Taenia NC parasitosis.
Seroepidemiological surveys carried out in Mexico have indicated a high percentage of individuals with antibodies against T. solium antigens in areas of porciculture, an observation which has been interpreted as frequent contact with cestode antigens (Larralde et al., 1992). Detailed studies in small rural communities have found up to 10% of individuals infected with adult tapeworms, high seropositivity rates, the presence of infected pigs reared domestically, as well as the practice of human defecation on open ground. Studies of small rural communities in Mexico indicate a significant association between the number of T. solium carriers and the practice of defecating on open ground (Sarti et al., 1992). The studies of Diaz-Camacho et al.
(1991) in small rural communities revealed that sharing living quarters with a tapeworm carrier increased the number of individuals with antibodies to cestode antigens five-fold over inhabitants who had no contact with such carriers. Daily domestic contact with a tapeworm carrier also increases the risk of acquiring NC, as has been shown by the studies of Sarti et al.
(1992). These results emphasize the importance of treating tapeworm carriers opportunely with anthelminthics. The elimination of T. solium tapeworms in endemic areas should become a public health priority, since it has been shown that persons living with a tapeworm carrier have a significantly higher risk of acquiring NC.
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