Malaria is transmitted by female mosquitoes in the genus Anopheles and is a major public health issue. Different species of Anopheles mosquitoes have different epidemiological characteristics, behaviors, and ecological requirements, and so an understanding of their biology and ecology in a particular area is critical for successful disease control. The aim of this study was to determine which environmental factors are associated with Anopheles larvae in a malaria-endemic area in Ratchaburi Province, Thailand, which shares a border with Myanmar. In October 2016, we collected mosquito larvae and measured six environmental factors at 10 study sites located along Lam Pachi River, which flows through Huay Nam Nak village in Ratchaburi Province. We found two species of Anopheles larvae (An. subpictus sensu lato (s.l.) Grassi and An. barbirostris s.l. van der Wulp) at 7 of the 10 study sites, the numbers of which significantly differed between sites (p < 0.05). Pearson correlation analysis showed that the numbers of larvae of both species were significantly positively correlated with the dissolved oxygen level (p < 0.01) and significantly negatively correlated with the width of the river (p < 0.05) and pH (p < 0.01). By contrast, turbidity, water depth, and water temperature were not associated with larval abundance. Mosquito species which belong to genus Anopheles are considered to be of public health and medical importance. Therefore, Anopheles mosquito surveillance and control in the study sites are essential. This information will facilitate vector-borne disease control and improve our understanding of the biology of Anopheles vectors in rivers located along international borders, further reducing the number of patients in this malaria-endemic area.

Anopheles (Cellia) dirus Peyton & Harrison and Anopheles baimaii Sallum & Peyton are sibling species within the Dirus complex belonging to the Leucosphyrus group, and have been incriminated as primary vectors of malaria in Thailand. In the present study, DNA barcoding and geometric morphometrics were used to distinguish between An. dirus and An. baimaii in the international border areas, Trat Province, eastern Thailand. Our results revealed that DNA barcoding based on the cytochrome c oxidase subunit I gene could not be used to distinguish An. dirus from An. baimaii. The overlapping values between intra- and interspecific genetic divergence indicated no barcoding gap present for An. dirus and An. baimaii (ranging from 0 to 0.99%). However, the results of the geometric morphometric analysis based on the wing shape clearly distinguished An. dirus and An. baimaii, with 92.42% of specimens assigned to the correct species. We concluded that geometric morphometrics is an effective tool for the correct species identification of these two malaria vectors. Our findings could be used to make entomological surveillance information more accurate, leading to further effective mosquito control planning in Thailand and other countries in Southeast Asia.

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The correct identification of mosquito species is important for effective mosquito vector control. However, the standard morphological identification of mosquito species based on the available keys is not easy with specimens in the field due to missing or damaged morphological features during mosquito collections, often leading to the misidentification of morphologically indistinguishable. To resolve this problem, we collected mosquito species across Thailand to gather genetic information, and evaluated the DNA barcoding efficacy for mosquito species identification in Thailand. A total of 310 mosquito samples, representing 73 mosquito species, were amplified using mitochondrial cytochrome c oxidase subunit I (COI) primers. The average maximum intraspecific genetic variation of the 73 mosquito species was 1% ranged from 0–5.7%. While, average minimum interspecific genetic variation (the distance to the nearest neighbour) of the 73 mosquito species was 7% ranged from 0.3–12.9%. The identification of success rates based on the “Best Match,” “Best Close Match,” and “All Species Barcodes” methods were 97.7%, 91.6%, and 81%, respectively. Phylogenetic analyses of Anopheles COI sequences demonstrated a clear separation between almost all species (except for those between An. baimaii and An. dirus), with high bootstrap support values (97%–99%). Furthermore, phylogenetic analyses revealed potential sibling species of An. annularis, An. tessellatus, and An. subpictus in Thailand. Our results indicated that DNA barcoding is an effective molecular approach for the accurate identification of mosquitoes in Thailand.

Chaiphongpachara T, Laojun S, Kunphichayadecha C. 2018. Effect of the CDC light trap on control of nocturnal mosquitoesin coastal Samut Songkhram Province, Thailand. Biodiversitas 19: 1750-1754. This study aimed to investigate the effect of CDC lighttrap on mosquito control and to study the relationship between this effect and weather factors in coastal areas (2 and 4 km from the sea)of Samut Songkhram Province, Thailand. We conducted a field test by trapping for 30 consecutive days from September to October2017. The trap was hung at a height of 1.5 m and was 50 m away from a house. A total of 2963 adult female mosquitoes of 4 speciesbelonging to 2 genera were trapped, including Anopheles epiroticus Linton & Harbach, Culex quinquefasciatus Say, Cx. sitiensWiedmann and Cx. gelidus Theobald. The trapping rate of the CDC light trap set up 2 km from the sea was 85.70±73.81 adultmosquitoes per night. Meanwhile, at the location 4 km from the sea, the trap collected 13.07±11.40 adult mosquitoes per night.Comparing the numbers of mosquitoes captured by the CDC light trap between these two sites, there was a significant difference at p <0.05. This study shows that the CDC light trap can be used for effective control of mosquitoes in coastal areas of Samut SongkhramProvince, Thailand, especially Cx. sitiens, a filariasis vector.