Parasitologic Surveys on Indian Reservations in Montana, South Dakota, New Mexico, Arizona, and Wisconsin

Dorothy M. Melvin Department of Health, Education and Welfare, Public Health Service, Communicable Disease Center, Atlanta, Georgia

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M. M. Brooke Department of Health, Education and Welfare, Public Health Service, Communicable Disease Center, Atlanta, Georgia

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Summary

The parasitologic results of stool examinations from 907 and anal swabs from 1324 Indians on five reservations in the United States have been tabulated. Sixty-nine percent of the Indians examined were positive for one or more organisms. The over-all percentage of Entamoeba histolytica was found to be 14.9% and the amebic prevalence rate (APR), used as an index of protozoan infection, was 53.5%. With the exception of Enterobius vermicularis, no helminths other than Hymenolepis nana and one infection of Trichuris were found. The prevalence rate for E. vermicularis was 16.0% and for H. nana, 3.7%.

The parasite rates are high even in the youngest group (0 to 5) and continue at a fairly high level throughout the various ages with a peak in the 6 to 9 year group. An age-sex distribution reveals that the peaks of E. histolytica and E. vermicularis rates occur in the 6 to 9 year group in both sexes; however, while the APR peak for males also occurs in this group, in females it is in the 20 to 44 age group. In general, the rates in females are higher than in the males.

No clear-cut correlation with environmental factors could be found, although crowding (2 or more persons per room) was associated with higher rates. Also, the rates may have been affected by poor toilet facilities, poor water supplies, and the inaccessibility of water within the home.

An indication of possible racial susceptibility was found in that the protozoa rates tended to increase directly with the proportion of Indian blood. E. vermicularis rates were higher in the part-Indian groups, however.

On four of the five reservations surveyed, the prevalence of intestinal protozoa is two to four times greater in the Indians than reported in surveys of non-Indian populations in the United States. The fifth, Lac Courte Oreilles, had a very low rate, the reasons for which are not clearly understood.

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