We investigated two mitochondrial genes (cytb and cox1), one plastid gene (tufA), and one nuclear gene (ldh) in blood samples from 12 chimpanzees and two gorillas from Cameroon and one lemur from Madagascar. One gorilla sample is related to Plasmodium falciparum, thus confirming the recently reported presence in gorillas of this parasite. The second gorilla sample is more similar to the recently defined Plasmodium gaboni than to the P. falciparum-Plasmodium reichenowi clade, but distinct from both. Two chimpanzee samples are P. falciparum. A third sample is P. reichenowi and two others are P. gaboni. The other chimpanzee samples are different from those in the ape clade: two are Plasmodium ovale, and one is Plasmodium malariae. That is, we have found three human Plasmodium parasites in chimpanzees. Four chimpanzee samples were mixed: one species was P. reichenowi; the other species was P. gaboni in three samples and P. ovale in the fourth sample. The lemur sample, provisionally named Plasmodium malagasi, is a sister lineage to the large cluster of primate parasites that does not include P. falciparum or ape parasites, suggesting that the falciparum + ape parasite cluster (Laverania clade) may have evolved from a parasite present in hosts not ancestral to the primates. If malignant malaria were eradicated from human populations, chimpanzees, in addition to gorillas, might serve as a reservoir for P. falciparum.T here is a revolution afoot concerning our understanding of human malaria. It was shown in 1994/1995 that the closest relative of Plasmodium falciparum, the agent of malignant malaria was Plasmodium reichenowi, a chimpanzee parasite, the only ape malaria parasite that had been molecularly characterized (1-4). The close phylogenetic relationship between P. falciparum and Plasmodium reichenowi, their distinctness from the three other known human malaria parasites (Plasmodium vivax, Plasmodium ovale, and Plasmodium malariae), as well as from other primate parasites, and their remoteness from bird or lizard parasites, was soon confirmed by other studies (5-7). It was assumed, as a working hypothesis, that P. falciparum and P. reichenowi had evolved from a common ancestor parasite, independently in their respective hosts, humans and chimpanzees, as these two lineages gradually diverged from one another over the last 5-7 million years-the cospeciation hypothesis. Two alternative hypotheseseither (i) a human origin (P. reichenowi evolved from an introduction of P. falciparum into chimpanzee hosts) or (ii) a chimpanzee origin (P. falciparum evolved from the introduction of P. reichenowi into the human lineage)-could not be tested against each other or against the cospeciation hypothesis, because only one P. reichenowi isolate was available, which had been isolated from a captive chimpanzee.It was soon demonstrated by Rich et al. (8), Rich and Ayala (9), and Ayala and Rich (10) that P. falciparum has very low levels of neutral genetic polymorphism, a result that was subsequently confirmed by other investigators (11...

Since the 1970's, the diversity of Plasmodium parasites in African great apes has been neglected. Surprisingly, P. reichenowi, a chimpanzee parasite, is the only such parasite to have been molecularly characterized. This parasite is closely phylogenetically related to P. falciparum, the principal cause of the greatest malaria burden in humans. Studies of malaria parasites from anthropoid primates may provide relevant phylogenetic information, improving our understanding of the origin and evolutionary history of human malaria species. In this study, we screened 130 DNA samples from chimpanzees (Pan troglodytes) and gorillas (Gorilla gorilla) from Cameroon for Plasmodium infection, using cytochrome b molecular tools. Two chimpanzees from the subspecies Pan t. troglodytes presented single infections with Plasmodium strains molecularly related to the human malaria parasite P. ovale. These chimpanzee parasites and 13 human strains of P. ovale originated from a various sites in Africa and Asia were characterized using cytochrome b and cytochrome c oxidase 1 mitochondrial partial genes and nuclear ldh partial gene. Consistent with previous findings, two genetically distinct types of P. ovale, classical and variant, were observed in the human population from a variety of geographical locations. One chimpanzee Plasmodium strain was genetically identical, on all three markers tested, to variant P. ovale type. The other chimpanzee Plasmodium strain was different from P. ovale strains isolated from humans. This study provides the first evidence of possibility of natural cross-species exchange of P. ovale between humans and chimpanzees of the subspecies Pan t. troglodytes.

A high (11.8%) level of hepatitis B virus (HBV) infection was found among 524 Pygmies in Cameroon, whereas the extent of hepatitis C virus (HCV) infection in the same population was low (0.6%). Phylogenetic analyses showed cocirculation of two HBV genotypes, HBV-A3 and -E. Taken together, our results suggest different epidemiological scenarios concerning HBV and HCV infections in this population.Sub-Saharan Africa is considered to be an area of high hepatitis B virus (HBV) and hepatitis C virus (HCV) endemicity (6, 11). However, to date little information has been available pertaining to the prevalence and genetic diversity of these viruses in central Africa. In Cameroon, HBV and HCV infections have been studied mostly among Bantu populations (4,13,15), and very few data are available for the Pygmies in this region. The Pygmies have lived in a forest environment in Cameroon for more than 20,000 years, mostly as hunter-gatherers (19). The characterization of HBV and HCV isolates from ancient populations may help to reveal the origin and evolutionary history of these viruses (7). Three distinct Pygmy groups currently live in Cameroon: the Baka, the Bakola, and the Bedzan. Three studies conducted 15 years ago reported a high HCV prevalence, ranging from 6 to 11%, in the Pygmy population (5, 10, 12). However, these studies only considered the Baka. Furthermore, the performances of the tests used at that time are questionable. A more recent study demonstrated an HCV prevalence of only 2.3% (8). In those 4 studies, Cameroon was found to be an area where HBV is highly endemic. Even now, no comparable information is available for the Bakola or Bedzan Pygmies. Thus, the objectives of our study were to assess the prevalence of HBV and HCV markers among the three Pygmy groups from Cameroon and also to study the HBV genetic diversity in these populations.This study formed part of a survey of viral emergence in Pygmies from Cameroon conducted from 2005 to 2008 (1-3). Informed consent was obtained from adults (or from parents, in the case of children) before blood sampling. Furthermore, the participants of the study underwent a medical examination and, if necessary, were treated according to local procedures on site or were sent to local medical facilities. The geographic localization, the number of subjects included in each group, the mean age, and the sex ratio are shown in Fig. 1A.The presence of antibodies against HCV (anti-HCV) was checked by the use of a third-generation enzyme immunoassay (EIA) (Monolisa anti-HCV Plus version 2; Bio-Rad, MarneLa-Coquette, France). A positive result for anti-HCV was defined as a Monolisa ratio of greater than 6 (16). Of the 346 available samples tested, only 2 (0.6%) (one Baka and one Bedzan; 95% confidence interval [CI], 0.9 to 1.9%) were anti-HCV positive. Those samples were negative when tested for HCV RNA.HBV surface antigen (HBsAg) was screened for by a thirdgeneration EIA (Monolisa AgHBs Plus; Bio-Rad). Of the 524 samples tested, 62 (11.8%) (95% CI, 9.2 to 14.9%) were positive. Th...

BackgroundWhile influenza surveillance has increased in most developing countries in the last few years, little influenza surveillance has been carried out in sub-Saharan Africa and no information is available in Central Africa. The objective of this study was to assess the prevalence of influenza viruses circulating in Yaounde, Cameroon and determine their antigenic and genetic characteristics.MethodsThroat and/or nasal swabs were collected from November 2007 to October 2008 from outpatients with influenza-like illness (ILI) in Yaounde, Cameroon and analyzed by two different techniques: a one-step real time reverse transcription-polymerase chain reaction (RT-PCR) and virus isolation in MDCK cells. Typing and subtyping of virus isolates was performed by hemagglutination inhibition (HI), and viruses were sent to the WHO Collaborating Centre in London, UK for further characterization and analyses of antiviral resistance by enzyme inhibition assay and nucleotide sequencing.ResultsA total of 238 patients with ILI were sampled. During this period 70 (29%) samples were positive for influenza by RT-PCR, of which only 26 (11%) were positive by virus isolation. By HI assay, 20 of the 26 isolates were influenza type A (10 H3N2 and 10 H1N1) and 6 were influenza type B (2 B/Victoria/2/87 lineage and 4 B/Yagamata/16/88 lineage). Seven (70%) of the H1N1 isolates were shown to be resistant to oseltamivir due to a H275Y mutation.ConclusionsThis study confirmed the circulation of influenza A(H1N1), A(H3N2) and B viruses in the human population in Central Africa and describes the emergence of oseltamivir-resistant A(H1N1) viruses in Central Africa.

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