Wild chimpanzees are infected with homologous types of human malaria

Abstract

BackgroundDespite ongoing - and in some regions escalating -morbidity and mortality associated with malaria para-sites, evolutionary epidemiology of Plasmodium is notwell characterized. Recent studies using molecularapproaches demonstrated that wild and captive gorillasand captive bonobos and chimpanzees are infected withP. falciparum and that these apes harbor parasitesbroadly related to P. falciparum[1]. Captive chimpanzeesand bonobos had malaria parasites related to humanP. ovale and P. malariae and various monkeys and onesemi-wild chimpanzee hadP. vivax[2]. It is not clearwhether these apes harbor naturally these parasites orwhether they are transmitted from humans. Most of theexamined animals had close contact with humans, com-parable studies in wild living apes are missing. We pro-vide the first survey ofPlasmodium diversity in wildchimpanzees living in an undisturbed tropical rainforestin Africa.MethodsWe examined tissue from 16 wild West African chim-panzees that lived in the Tai National Park, Ivory Coast,where human contact with animals is limited toresearchers who access the territory only during the day.Samples were collected from animals that died primarilyfrom anthrax or respiratory disease. Generic real timePCR assay was used to detect all knownPlasmodiumspecies.Results11/16 (68%) animals tested positive. Sequence analysesof cytB and 18S rRNA genes identifiedP. malariae,P. ovale, P. vivax, P. gaboni, P. reichenowi, P. billcollinsiand P. billbraii.DiscussionPrevious examination of the role of our closest phyloge-netic relatives, the great apes, in the evolution andpersistence of human malarias has been limited by a lackof data from wild ape populations. Interpretation ofpatterns of malaria infection in captive ape populationsmust consider ample opportunities for human to apetransmission, negating the opportunity to investigate theevolutionary origins and public health-related risks ofthese parasites. Our examination of malaria parasites inwild chimpanzees demonstrates that these apes are mostlikely naturally infected with Plasmodium species homolo-gous toP. malariae, P. vivaxand P. ovale as well asP. falciparum. Whether wild great apes are the origin ofthese malaria types requires further investigation but theymay act as reservoir of infection. These results haveimportant implications for global efforts underway to era-dicate malaria in humans including vaccine developmentbased on animal variants of human parasites.