Inferring the evolutionary history of Indian Plasmodium vivax from population genetic analyses of multilocus nuclear DNA fragments

The human malaria parasite Plasmodium vivax is globally widespread, causing high malaria morbidity. As P.vivax is highly endemic to India, and previous reports indicate genetic homogeneity in population samples, we tested the hypothesis of no genetic structuring in Indian P.vivax. Further, based on the reports of increasing incidence of Plasmodium falciparum infection in comparison with P.vivax in recent years in India, it was important to understand whether reduction in population size has resulted in decrease in P.vivax infection rate in India. For this, we utilized recently developed putatively neutral markers from chromosome 13 of P.vivax to score single nucleotide polymorphisms in 126 P.vivax isolates collected from 10 different places in India. The overall results indicated that Indian P.vivax bears high nucleotide diversity within population samples but moderate amount of genetic differentiation between population samples. STRUCTURE analysis grouped 10 population samples into three clusters based on the proportion of the genetic ancestries in each population. However, the pattern of clustering does not correlate with sampling locations in India. Furthermore, analyses of past demographic events indicated reduction in population size in majority of population samples, but when isolates from all the 10 samples were considered as a single population, the data fit to the demographic equilibrium model. All these observations clearly indicate that Indian P.vivax presents complex evolutionary history but possesses several features of being a part of ancestral distribution range of this species.