Anopheles moucheti and Anopheles vinckei Are Candidate Vectors of Ape Plasmodium Parasites, Including Plasmodium praefalciparum in Gabon

Abstract

During the last four years, knowledge about the diversity of Plasmodium species in African great apes has considerably increased. Several new species were described in chimpanzees and gorillas, and some species that were previously considered as strictly of human interest were found to be infecting African apes. The description in gorillas of P. praefalciparum, the closest relative of P. falciparum which is the main malignant agent of human malaria, definitively changed the way we understand the evolution and origin of P. falciparum. This parasite is now considered to have appeared recently, following a cross-species transfer from gorillas to humans. However, the Plasmodium vector mosquito species that have served as bridge between these two host species remain unknown. In order to identify the vectors that ensure ape Plasmodium transmission and evaluate the risk of transfer of these parasites to humans, we carried out a field study in Gabon to capture Anopheles in areas where wild and semi-wild ape populations live. We collected 1070 Anopheles females belonging to 15 species, among which An. carnevalei, An. moucheti and An. marshallii were the most common species. Using mtDNA-based PCR tools, we discovered that An. moucheti, a major human malaria vector in Central Africa, could also ensure the natural transmission of P. praefalciparum among great apes. We also showed that, together with An. vinckei, An. moucheti was infected with P. vivax-like parasites. An. moucheti constitutes, therefore, a major candidate for the transfer of Plasmodium parasites from apes to humans.

Plasmodium falciparum -like parasites infecting wild apes in southern Cameroon do not represent a recurrent source of human malaria

“…The discovery of this previously unrecognized reservoir has prompted concerns that wild-living apes might constitute a source of recurrent human infection (4,5,9,(11)(12)(13). In this study, we set out to examine this possibility for several reasons.…”

“…Depending on the host, parasite, and/or vector properties required for successful transmission, a much larger number of individuals from geographically more diverse regions will have to be screened to exclude rare spillovers. Because the Anopheles species that transmit Plasmodium parasites among wild apes are only beginning to be characterized (11), it is conceivable that the ecology, distribution, and feeding preferences of these vectors play a much greater role in determining the likelihood of zoonotic transmission than the mere geographic proximity of human habitations to infected ape populations. Nonetheless, it seems unlikely that the absence of zoonotic Laverania infections in rural Cameroon is solely due to a lack of human exposure.…”

“…Moreover, P. praefalciparum was shown to be the immediate precursor of human P. falciparum (4). Because candidate Anopheles vectors have been identified that may transmit both ape and human parasites (11), the fact that a large fraction of wild-living apes is endemically Plasmodium infected has raised concerns that they might represent a source of recurring human infections (4,5,9,12,13).…”

Mosquito Vectors and the Globalization of Plasmodium falciparum Malaria

“…This more intricate hypothesis seems less likely (78). The mosquito vector responsible for the initial transmission between gorillas and humans has not been identified, but Anopheles moucheti, A. vinckei, and A. marshallii, have been proposed as a candidate because P. praefalciparum has been detected in mosquitoes of this species recovered in the wild (50,54,74 (67), allowing for ideal breeding conditions for mosquito vectors. At about the same time, the human population density increased owing to the spread of slash-and-burn (swidden) agriculture (89), an important factor in increasing the ease of transmission and promoting the evolution of higher virulence phenotypes (84).…”

Ape malaria transmission and potential for ape-to-human transfers in Africa

“…Nevertheless, several authors have speculated that some of the main human vector species in forested areas of west and central Africa could be also involved in ape Plasmodium transmission (5). This is particularly the case of Anopheles moucheti and species from the Anopheles nili group that have overlapping habitats with great apes (11,12).…”