E. bieneusi infection was common in HIV-infected patients with diarrhea in Zimbabwe and may be acquired through person-to-person and fecal-oral transmission.

The long-term impact of annual case-finding and chemotherapy with praziquantel on schistosomiasis japonica was examined in an 8-year longitudinal study in the Philippines. The prevalence, incidence, and intensity of infection and schistosome-induced hepatomegaly significantly decreased within 3-4 years of treatment and then stabilized despite continual population-based chemotherapy. Hepatomegaly rapidly developed in acutely infected persons, with 82% of subjects developing hepatic enlargement within 2 years of reinfection. These data suggest that abrupt discontinuation of current control measures in the Philippines may result in a rapid rebound in morbidity. Age-dependent acquired resistance to reinfection also developed in subjects chronically exposed to schistosomiasis japonica, suggesting that a vaccine may represent an alternative approach for control of this parasitic infection.

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Paramyosin, a 97 kDa myofibrillar protein, is a candidate vaccine antigen for prevention of infection with the human parasite Schistosoma mansoni. To determine if paramyosin would also induce protection against Schistosoma japonicum, paramyosin was biochemically purified from S. japonicum adult worms. SDS-PAGE demonstrated a single protein with a molecular weight of 97 kDa. In four separate experiments, vaccination of mice with S. japonicum paramyosin without adjuvant induced significant resistance (62%-86%, P < 0.001) against cercarial challenge as compared to controls. These data suggest that S. japonicum paramyosin may represent a candidate vaccine for immunization against schistosomiasis japonica.

Trichuris trichiura is an helminthic infection with potentially severe health consequences. The hypothesis that host genetic factors can account for the distribution of Trichuris was tested using familial data on egg counts available for two populations, the Jirels of Nepal and the population of Jishan Island in Jiangxi Province of the People's Republic of China. Whipworm is highly prevalent in the Jishan Island population (86%), but occurs at a low rate in the Jirel population (14%). A quantitative genetic analysis was performed on each data set, using a variance component approach. Approximately 28% of the variation in Trichuris trichiura loads was attributable to genetic factors in both populations. Common household effects accounted for only 4% of the variation in the Jirels and none of the variation in the Jishan Island population. These concordant results from two separate populations provide strong evidence of the important role of genetics in determining differential susceptibility to whipworm infection.

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