Identification of Plasmodium malariae, a Human Malaria Parasite, in Imported Chimpanzees

Toshiyuki Hayakawa,Hirohisa Hirai,Tomoko Toyama,Toshihiro Horii,Kazuyuki Tanabe,Toshifumi Udono,Nobuko Arisue,Jetsumon Sattabongkot,Takafumi Tsuboi,Gordon Langsley

doi:10.1371/journal.pone.0007412

Abstract

It is widely believed that human malaria parasites infect only man as a natural host. However, earlier morphological observations suggest that great apes are likely to be natural reservoirs as well. To identify malaria parasites in great apes, we screened 60 chimpanzees imported into Japan. Using the sequences of small subunit rRNA and the mitochondrial genome, we identified infection of Plasmodium malariae, a human malaria parasite, in two chimpanzees that were imported about thirty years ago. The chimpanzees have been asymptomatic to the present. In Japan, indigenous malaria disappeared more than fifty years ago; and thus, it is most likely inferred that the chimpanzees were infected in Africa, and P. malariae isolates were brought into Japan from Africa with their hosts, suggesting persistence of parasites at low level for thirty years. Such a long term latent infection is a unique feature of P. malariae infection in humans. To our knowledge, this is the first to report P. malariae infection in chimpanzees and a human malaria parasite from nonhuman primates imported to a nonendemic country.

Highlights

Malaria is a major infectious disease prevalent in most tropical and subtropical areas in the world
Molecular diagnosis for the presence of malaria parasites was carried out using polymerase chain reactions (PCRs) that amplify the mitochondrial genome and nuclear-encoded small subunit (SSU) rRNA gene of all known malaria parasites
Takaboh and Oumu have shown no symptoms of malaria to the present while in Japan

Summary

Introduction

Malaria is a major infectious disease prevalent in most tropical and subtropical areas in the world. Genus Plasmodium, infect all classes of terrestrial vertebrates (i.e. mammals, birds, and reptiles)[1]. The four classical human malaria parasites, Plasmodium falciparum, Plasmodium vivax, Plasmodium malariae, and Plasmodium ovale, are widely believed to infect only man as a natural host. Earlier studies described several human malaria parasite-like species from great apes: Plasmodium reichenowi, a P. falciparum-like parasite in chimpanzees, Plasmodium schwetzi, a P. vivax/P. ovale-like parasite in chimpanzees and gorillas, and Plasmodium rodhaini, a P. malariaelike parasite in chimpanzees [2,3]. Surveys of malaria parasites in great apes are required. The investigation of malaria infection in great apes should be helpful for the primates’ health and biodiversity conservation efforts

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Conclusion