Four species of Plasmodium parasites cause malaria in humans, but Plasmodium falciparum is responsible for almost all human malaria mortality, killing more than 1 million people each year. However P. falciparum is only distantly related to the other three Plasmodium species that cause malaria in humans, whereas P. reichenowi, a parasite of chimpanzees and gorillas, is morphologically almost indistinguishable from P. falciparum. This remarkably close relationship has been confirmed by molecular phylogenetic studies and P. reichenowi sequences are therefore very powerful outgroups for P. falciparum genetic diversity studies aimed at identifying P. falciparum genes under immune selection pressure. The parallels between the organisms are also of great interest in understanding specific aspects of P. falciparum pathogenesis. However, although P. reichenowi was observed in the blood of wild chimpanzees on several occasions in the early 20th century, only a single P. reichenowi isolate has ever been obtained by the scientific community, and only a handful of frozen tubes of that isolate remain at CDC. Although some limited P. reichenowi genome sequence is available, generated using these frozen stocks, it consists largely of short fragments and is heavily contaminated with chimpanzee DNA. Work on the P. reichenowi genome has ceased until new sources of P. reichenowi DNA can be found. New P. reichenowi isolates are therefore urgently needed to complete the P. reichenowi genome sequence, as well as for comparative genetic and pathogenesis studies. In order to obtain new P. reichenowi isolates we need to identify wild chimpanzee populations in which P. reichenowi infections occur, but no prevalence study of P. reichenowi infection in wild chimpanzees has ever been carried out. The protected status of chimpanzees places strict limits on the samples that can be obtained for such studies. The objective of this application is to employ a unique, non-invasive and ethically sensitive assay to establish the prevalence of P. reichenowi infection in wild chimpanzee communities. To achieve this objective we have developed a novel assay that uses urine samples to detect Plasmodium infection. We propose to apply this assay to a unique and pre-existing collection of chimpanzee urine and fecal samples.
Our specific aims are: 1. Establish the sensitivity of using urine samples to detect past Plasmodium infections. 2. Establish the prevalence and distribution of P. reichenowi in wild chimpanzee populations. This project is expected to define for the first time the prevalence and distribution of P. reichenowi infection in wild chimpanzees. It is also expected to lead directly to the identification of new P. reichenowi isolates that would be made freely available to the malaria research community. Such isolates would be an outstanding and unique resource for understanding of the evolution and pathogenesis of one of the most important human infectious disease killers, Plasmodium falciparum. Plasmodium falciparum parasites kill more than 1 million people each year. In order to understand P. falciparum virulence and pathogenicity we need to compare it with closely related parasite species, but the parasite most closely related to P. falciparum, a chimpanzee parasite called P. reichenowi, has only ever been isolated once and only limited stocks of that isolate remain. The objective of this application is to establish the prevalence of P. reichenowi infection in wild chimpanzees and to use that information to obtain new P. reichenowi isolates that would be made available to the malaria research community for comparative studies.
| Rayner, Julian C; Liu, Weimin; Peeters, Martine et al. (2011) A plethora of Plasmodium species in wild apes: a source of human infection? Trends Parasitol 27:222-9 |
| Liu, Weimin; Li, Yingying; Learn, Gerald H et al. (2010) Origin of the human malaria parasite Plasmodium falciparum in gorillas. Nature 467:420-5 |
