Humans frequently exposed to a range of non-human primate malaria parasite species through the bites of Anopheles dirus mosquitoes in South-central Vietnam

Abstract

BackgroundRecent studies have described natural human infections of the non-human primate parasites Plasmodium knowlesi and Plasmodium cynomolgi. In Southeast Asia, mosquitoes of the Anopheles leucosphyrus group bite both humans and monkeys in the forest and thus offer a possible route for Plasmodium species to bridge the species barrier. In this study we analysed the species composition of malarial sporozoites infecting the salivary glands of Anopheles dirus in order to determine their potential role as bridge vectors of Plasmodium parasites from monkeys to humans.MethodsMosquitoes were collected in the forest and forest fringe area of Khanh Phu commune by human-baited landing collection. Anopheles species were determined on the basis of morphologic features. Sporozoite-infected salivary glands were applied to filter paper and dried in an ambient atmosphere, before storage in closed vials at 4–6 °C. Detection and identification of Plasmodium species in salivary glands were carried out by nested-PCR of the small subunit ribosomal RNA gene.ResultsSix species of Plasmodium parasites were detected by PCR, of which P. vivax was the most common, followed by P. knowlesi, P. inui, P. cynomolgi, P. coatneyi and P. falciparum. Twenty-six of the 79 sporozoite infected mosquitoes showed multiple infections, most of which were a combination of P. vivax with one or more of the non-human primate Plasmodium species.ConclusionsThese results suggest that humans overnighting in this forest are frequently inoculated with both human and non-human primate malaria parasites, leading to a situation conducive for the emergence of novel zoonotic malaria.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-015-0995-y) contains supplementary material, which is available to authorized users.

Predicting the geographical distributions of the macaque hosts and mosquito vectors of Plasmodium knowlesi malaria in forested and non-forested areas

“…The An. dirus biting and infection rates did not differ significantly between a forest site and a forest fringe site in Khanh Hoa Province, Vietnam [ 64 ], whereas An. cracens was more abundant and had a higher human biting rate at an orchard site compared to a forest edge and village site in Pahang State, Malaysia [ 19 ].…”

Analysis of clinical malaria disease patterns and trends in Vietnam 2009–2015

“…A study in Cambodia reported significant clusters of high malaria risk located along the Cambodian–Vietnamese border and the Sesan River [ 49 ]. Migrant workers, many who live in forested borer regions, have been reported to be at particularly high risk of malaria and may have poor knowledge of malaria and limited access to preventive and therapeutic services [ 6 , 10 , 11 ]. In addition, cross border malaria is likely to contribute to the spread of anti-malarial drug-resistance in Viet Nam [ 50 , 51 ] through importation of multi-drug resistant malaria from Cambodia [ 52 , 53 ].…”

“…Despite the success in malaria control across the Greater Mekong Subregion (GMS), including Cambodia, China (Yunnan Province and Guangxi Zhuang Autonomous Region), Lao People’s Democratic Republic, Myanmar, Thailand and Viet Nam, a significant proportion of the region’s population live in malaria endemic areas, with approximately 70% of the local population at risk of contracting malaria, including 26% [ 1 , 2 ] at high risk (> 1 cases per 1000 population) [ 3 ]. Some of the drivers of malaria in the GMS include favourable environmental conditions for mosquitoes competent of transmitting malaria [ 4 , 5 ], frequent unchecked cross-border movement of people [ 6 – 9 ], movement of workers into forested border regions [ 6 , 10 , 11 ] and socioeconomic inequality [ 7 , 9 , 12 ]. In addition, the emergence of Plasmodium falciparum resistant to some or all anti-malarial drugs in the region has been extremely concerning [ 13 – 17 ].…”

Human and Simian Malaria in the Greater Mekong Subregion and Challenges for Elimination

“…Studies were conducted in the forest and forest-fringe areas near Nga Hai village where both human malaria parasites, P. falciparum and P. vivax, were found along with P. knowlesi in order to determine the potential role of An. dirus as bridge vectors of Plasmodium parasites from monkeys to humans [126]. Based on these studies, it was possible for An.…”