Abstract
BackgroundHuman 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.MethodsAnopheles 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.ResultsTwenty-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.ConclusionA 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.
Highlights
IntroductionThe 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
Human malaria is still a burden in Dak Nong and Binh Phuoc Provinces in south-central Vietnam that border Cambodia
No Anopheles specimens were found to be infected by either P. knowlesi or P. falciparum in the present study; malaria cases are still reported in Dak Nong Province, and in a similar survey conducted in that province in 2007, using the conventional PCR method of Cunha et al [41], we found that 2.03% (5/246) of the Anopheles females collected were infected with P. vivax: An. minimus (3/76) and An. maculatus (2/22) (CTN & SM, unpublished data)
Summary
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. Despite a decline in human malaria cases in Vietnam, malaria transmission continues in the forested areas of the southern and central provinces [1,2,3,4,5] where it is a significant public health and economic problem [6]. Several factors contribute to the maintenance of malaria transmission in this region of Vietnam, including a high density of the main vector Anopheles dirus [3,7,8], migration of people from malaria endemic areas [9] and failure to use preventive measures while working in the forest [10]. Malaria caused by P. knowlesi may represent an additional challenge for malaria control in forested areas where An. dirus and the natural hosts of P. knowlesi (macaque monkeys) co-occur, and zoonotic transmission of P. knowlesi could continue in the absence (or elimination) of P. falciparum and P. vivax
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