Malaria vectors of Papua New Guinea

Abstract

Understanding malaria transmission in Papua New Guinea (PNG) requires exact knowledge of which Anopheles species are transmitting malaria and is complicated by the cryptic species status of many of these mosquitoes. To identify the malaria vectors in PNG we studied Anopheles specimens from 232 collection localities around human habitation throughout PNG (using CO 2 baited light traps and human bait collections). A total of 22,970 mosquitoes were individually assessed using a Plasmodium sporozoite enzyme-linked immunosorbent assay to identify Plasmodium falciparum, Plasmodium vivax and Plasmodium malariae circumsporozoite proteins. All mosquitoes were identified to species by morphology and/or PCR. Based on distribution, abundance and their ability to develop sporozoites, we identified five species as major vectors of malaria in PNG. These included: Anopheles farauti, Anopheles hinesorum (incriminated here, to our knowledge, for the first time), Anopheles farauti 4, Anopheles koliensis and Anopheles punctulatus. Anopheles longirostris and Anopheles bancroftii were also incriminated in this study. Surprisingly, An. longirostris showed a high incidence of infections in some areas. A newly identified taxon within the Punctulatus Group, tentatively called An. farauti 8, was also found positive for circumsporozoite protein. These latter three species, together with Anopheles karwari and Anopheles subpictus, incriminated in other studies, appear to be only minor vectors, while Anopheles farauti 6 appears to be the major vector in the highland river valleys (>1500 m above sea level). The nine remaining Anopheles species found in PNG have been little studied and their bionomics are unknown; most appear to be uncommon with limited distribution and their possible role in malaria transmission has yet to be determined.