Human Ancylostoma infections in Nigeria.

An estimate of the proportion of infections with Ancylostoma duodenale and Necator americanus by the examination of larvae collected from the stools of 220 persons infected with hookworm was made. Fifty-nine per cent of the infections were due to N. americanus only: A. duodenale always occurred in association with N. americanus. In 12% of the infections it is suggested that there were approximately three female A. duodenale to 95 female N. americanus. The highest numbers of A. duodenale in mixed infections (28 female A. duodenale with 45 female N. americanus) occurred in only 1% of the infections. Evidence is given that egg size can be important in the differentiation of the two species. A method of calculating the proportion of the two hookworms, and hence of other intestinal nematodes, in mixed infections in an individual as well as in the general population, is also described.