Genetic structure of populations of the human hookworm, Necator americanus, in China.

Twenty-one to 58 individual Necator americanus were sampled from each of four villages in south-western China. Each nematode was sequenced for 588 bp of the mitochondrial cytochrome oxidase I gene. Allelic and nucleotide diversity varied two-fold among villages. Overall FST among populations was approximately 0.28, but this large value resulted from one low-diversity population that had a large genetic distance to the other three populations (F(ST) = 0.10 without that population). There was no correlation between geographical and genetic distance among sites. Thus, the genetic structure of this species in China may be characterized by variable effective sizes and uneven movement among sites. We discuss the implications of this genetic structure for vaccine development and the spread of drug resistance in human hookworms, and compare the genetic structure of hookworms with that of other nematodes.