Multispecies Plasmodium infections of humans

We analyzed point-prevalence data from 19 recent studies of human populatio ns in which either Plasmodium ovale or Plasmodium vivax co-occur with Plasm odium falciparum and Plasmodium malariae. Although the only statistical int eractions among sympatric congeners are pairwise, the frequencies of mixed- species infections relative to standard hypotheses of species sampling inde pendence show no strong relation to overall malaria prevalence. The strikin g difference between the P. falciparum-P. malariae-P. ovale and the P. falc iparum-P. malariae-P. vivax data is that the first typically shows a statis tical surplus of mixed-species infections and the second a deficit. This su ggests that the number of Plasmodium species present in a human population may be less important in determining the frequencies of mixed-species infec tions than is the identity of those species.