Population genomics reveal distinct and diverging populations of An. minimus in Cambodia.

Anopheles minimus is an important malaria vector throughout its wide geographic range across Southeast Asia. Genome sequencing could provide important insights into the unique malaria transmission dynamics in this region, where many vector species feed and rest outdoors. We describe results from a study using Illumina deep whole-genome sequencing of 302 wild-caught An. minimus collected from three Cambodian provinces over several years (2010, 2014, 2016) and seasons to examine the level of population structure and genetic diversity within this species. These specimens cluster into four distinct populations of An. minimus s.s., with two populations overlapping geographically. We describe the underlying genetic diversity and divergence of these populations and investigated the genetic variation in genes known to be involved in insecticide resistance. We found strong signals of selection within these An. minimus populations, most of which were present in the two Northeastern Cambodian populations and differ from those previously described in African malaria vectors. Cambodia is the focus of the emergence and spread of drug-resistant malaria parasites, so understanding the underlying genetic diversity and resilience of the vectors of these parasites is key to implementing effective malaria control and elimination strategies. These data are publicly available as part of the MalariaGEN Vector Observatory, an open access resource of genome sequence data.

Cow-baited tents are highly effective in sampling diverse Anopheles malaria vectors in Cambodia.

BACKGROUND: The accurate monitoring and evaluation of malaria vectors requires efficient sampling. The objective of this study was to compare methods for sampling outdoor-biting Anopheles mosquitoes in Cambodia. METHODS: In the Cambodian provinces of Pursat, Preah Vihear, and Ratanakiri, six different mosquito trapping methods were evaluated: human landing collection (HLC), human-baited tent (HBT), cow-baited tent (CBT), CDC miniature light trap (LT), CDC miniature light trap baited with molasses and yeast (LT-M), and barrier fence (F) in a Latin square design during four or six consecutive nights at the height of the malaria transmission season. RESULTS: Using all traps, a total of 507, 1175, and 615 anophelines were collected in Pursat, Preah Vihear, and Ratanakiri, respectively. CBTs captured 10- to 20-fold more anophelines per night than the other five sampling methods. All 2297 Anopheles mosquitoes were morphologically identified and molecularly typed using standard morphological keys and sequencing the rDNA ITS2 region to distinguish cryptic species, respectively. Overall, an extremely diverse set of 27 known Anopheles species was sampled. CBTs captured the same molecular species that HLCs and the other four traps did, as well as additional species. Nine specimens representing five Anopheles species (Anopheles hyrcanus, Anopheles barbirostris sensu stricto, Anopheles barbirostris clade III, Anopheles nivipes, and Anopheles peditaeniatus) were infected with Plasmodium falciparum and were exclusively captured in CBTs. CONCLUSIONS: These data indicate that cow-baited tents are highly effective in sampling diverse Anopheles malaria vectors in Cambodia. This sampling method captured high numbers of anophelines with limited sampling effort and greatly reduced human exposure to mosquito bites compared to the gold-standard human landing collection.