Diversity of Anopheles mosquitoes in Binh Phuoc and Dak Nong Provinces of Vietnam and their relation to disease

Abstract

Background: Human malaria is still a burden in Dak Nong and Binh Phuoc Provinces in south-central Vietnam that border Cambodia. Several Anopheles species that transmit human malarial Plasmodium may also transmit Wuchereria bancrofti, the nematode that causes Bancroftian lymphatic filariasis. The objective of this study was to investigate the role of Anopheles species in the transmission of these two pathogens in the two highly malaria endemic provinces of Vietnam.

Methods: Anopheles mosquitoes were collected in Dak Nong and Binh Phuoc Provinces in November and December of 2010 and 2011. Human landing catches, paired collections on human and buffalo, and resting captures were made with mouth aspirators. Collections were also made with light traps. Morphological and PCR-based methods were used to identify the species. Real-time PCR was used to detect Plasmodium species and W. bancrofti in individual mosquitoes.

Results: Twenty-four Anopheles species were identified among 797 captured mosquitoes. Anopheles dirus was found in both provinces and was the predominant species in Binh Phuoc Province; An. maculatus was the most prevalent species in Dak Nong Province. Anopheles minimus was collected only in Binh Phuoc Province. Some specimens of An. minimus and An. pampanai were misidentified based on morphology. Four specimens of An. scanloni were identified, and this is the first report of this species of the Dirus Complex in Vietnam. Two females, one An. dirus and one An. pampanai, collected in Binh Phuoc Province were infected with P. vivax, for an overall infection rate of 0.41% (2/486): 0.28% for An. dirus (1/361) and 20% for An. pampanai (1/5). No mosquitoes were found to be infected with P. falciparum, P. knowlesi or W. bancrofti in either province.

Conclusion: A diversity of Anopheles species occurs in Dak Nong and Binh Phuoc Provinces of Vietnam, several of which are considered to be actual and potential vectors of malarial protozoa and microfilariae. It is highly likely that two of the species, An. dirus and An. pampanai, are active in malaria transmission based on the detection of P. vivax in females of these species. This is the first report of An. scanloni in Vietnam.

Figure 1

Multiplex allele-specific PCR products on 2% agarose gel showing specimens of An. pampanai (A), An. scanloni (B) and An. rampae (C) collected in south-central Vietnam.

Figure 2

Anopheles species composition in south-central Vietnam based on molecular identification. (A) Prevalence of the malaria vectors and other taxa; (B) percentage of the “other” 21 species displayed in (A) (arranged alphabetically from bottom to top).

Figure 3

Amplification curves in the multiplex real-time PCR for two mosquitoes positive for P. vivax. (A) An. 1, Anopheles dirus; (B) An. 2, Anopheles pampanai; and (C) amplification of cytochrome oxidase cox I fragment by conventional PCR of P. vivax detected in Anopheles females collected in Vietnam. Pf and Pv = positive controls for P. falciparum and P. vivax.