Distribution of mosquitoes (Diptera: Culicidae) in Thailand: a dataset.

Mosquitoes play a crucial role as primary vectors for various infectious diseases in Thailand. Therefore, accurate distribution information is vital for effectively combating and better controlling mosquito-borne diseases. Here, we present a curated dataset of the mosquito distribution in Thailand comprising 12,278 records of at least 117 mosquito species (Diptera: Culicidae). The main genera included in the dataset are Aedes, Anopheles, Armigeres, Culex, and Mansonia. From 2007 to 2023, data were collected through routine mosquito surveillance and research projects from 1,725 locations across 66 (out of 77) Thai provinces. The majority of the data were extracted from a Thai database of the Thailand Malaria Elimination Program. To facilitate broader access to mosquito-related data and support further exploration of the Thai mosquito fauna, the data were translated into English. Our dataset has been published in the Global Biodiversity Information Facility, making it available for researchers worldwide.

Synergistic Behavioral Response Effect of Mixtures of Andrographis paniculata, Cananga odorata, and Vetiveria zizanioides against Aedes aegypti (Diptera: Culicidae).

Each binary mixture formulation of Vetiveria zizanioides (L.) Nash (VZ) with Andrographis paniculata (Burm.f.) Wall. ex Nees (AP) or Cananga odorata (Lam.) Hook.f. & Thomson (CO) and AP with CO at 1:1, 1:2, 1:3, and 1:4 ratios (v:v) was investigated for behavioral responses on laboratory and field strains of Aedes aegypti. Irritant and repellent activities of each formulation were compared with N,N-diethyl-3-methylbenzamide (DEET) using an excito-repellency test system. The result demonstrated that the mixture of VZ:AP in all combination ratios was the most effective in inducing an irritancy response against the laboratory strain (56.57-73.33%). The highest percentage of escaped mosquitoes exposed to the mixture at a 1:4 ratio (73.33%) was significantly different from DEET (26.67%) (p < 0.05). Against the field strain, the strongest escape response of AP:CO at a 1:1 ratio in the contact trial (70.18%) was significantly different compared with DEET (38.33%) (p < 0.05). There was a weak non-contact escape pattern in all combinations of VZ:CO against the laboratory strains (6.67-31.67%). These findings could lead to the further development of VZ and AP as active ingredients in a repellent that could advance to human use trials.

Comparing Light-Emitting-Diodes Light Traps for Catching Anopheles Mosquitoes in a Forest Setting, Western Thailand.

Light traps are a common method for attracting and collecting arthropods, including disease vectors such as mosquitoes. Various types of traps have been used to monitor mosquitoes in a forest in Western Thailand. In this study, four Light Emitting Diodes (LED) light sources (UV, blue, green, and red) and two fluorescent lights (white and UV) were used to trap nocturnal adult mosquitoes. These traps were used with light alone and not any additional attractant. The experiment was conducted from 18:00 to 06:00 h. on six consecutive nights, every two months, across dry, wet, and cold seasons. All specimens were first identified by morphological features and subsequently confirmed by using PCR. We collected a total of 873 specimens of 31 species in four genera, Anopheles, Aedes, Culex, and Armigeres. Anopheles harrisoni was the predominant species, followed by Aedes albopictus, Culex brevipalpis, Culex nitropunctatus, and Armigeres (Leicesteria) longipalpis. UV fluorescent light was the most effective light source for capturing forest mosquitoes, followed by UV LED, blue LED, green LED, white fluorescent, and red LED. The optimal times for collection were from 21:00 to 03:00 h in the dry season. Our results demonstrate that appropriate sampling times and light sources should be selected for optimal efficiency in vector surveillance programs.

Avoidance Behavior to Guava Leaf Volatile Oil by Three Medically Important Mosquito Vectors.

Volatile organic compounds from various plants have received popular interest as one of the vector control tools due to their eco-friendliness and insect-repellent activities. In this study, an excito-repellency assay system was used to examine the noncontact repellency, contact excitation, and knockdown (KD) effects of guava leaf (Psidium guajava L.) oil against Anopheles minimus (Theobald), Anopheles epiroticus (Linton & Harbach), and Culex quinquefasciatus (Say). The organic components of guava oil were identified by gas chromatography-mass spectrometry analysis with dl-limonene (17.4%), cymene (5.49%), and α-terpinene (5.20%) as the major constituents. At concentrations of 2.5 and 5.0%, 100% escape of An. minimus was recorded in the contact assay and 96-98% escape in the noncontact assay. Guava oil stimulated potent irritant (92% escape) and repellent (61-86% escape) effects against Cx. quinquefasciatus. A lower repellency action was observed against An. epiroticus (17-20% escape). No KD effect was observed for guava oil against An. minimus and Cx. quinquefasciatus at any concentration. However, An. epiroticus was more prone to KD effects, with the highest percentage KD (44% in nonescape group) observed with 5.0% guava oil in the noncontact assay. Mortalities of 35% and 11% were observed for An. epiroticus in the nonescape groups in the contact and noncontact assays, respectively. Concentrations of 1.0% and 2.5% guava oil led to <2% mortality in An. minimus. Our findings highlight guava oil as a promising plant-based mosquito repellent that can be included in insecticide formulations for future mosquito control programs.

Transmitted Light as Attractant with Mechanical Traps for Collecting Nocturnal Mosquitoes in Urban Bangkok, Thailand.

Mosquito surveillance is the cornerstone for determining abundance, species diversity, pathogen infection rates, and temporal and spatial distribution of different life stages in an area. Various methods are available for assessing adult mosquito populations, including mechanical trap devices using different forms of attractant cues (chemical and visual) to lure mosquitoes to the trap. So-called "light traps" use various electromagnetic wavelengths to produce a variety of visible spectral colors to attract adult mosquitoes. However, this type of trapping technology has not been widely used in Thailand. This study compared the efficacy of 4 light-emitting diodes (LEDs) (blue, green, yellow, and red) and 2 fluorescent (ultraviolet [UV] and white) lights for collecting mosquitoes in urban Bangkok. Using a Latin square experimental design, 6 light traps equipped with different lights were rotated between 6 trap site locations within the Kasetsart University (KU) campus. Each location received 6 replicate collections (6 consecutive trap-nights represented 1 replicate) over 36 collection nights for a total of 216 trap-nights. Traps were operated simultaneously (1800 to 0600 h), with captured mosquitoes removed at 3-h intervals. In total, 2,387 mosquitoes consisting of 11 species across 5 genera (Aedes, Anopheles, Armigeres, Culex, and Mansonia) were captured. Collectively, Culex species represented the predominant group sampled (2,252; 94.4%). The UV light source captured 1,544 (64.7%) of the total mosquitoes collected, followed by white 389 (16.3%), with the 4 LED sources collecting between 6.8% (blue) and 1.9% (yellow). Traps equipped with UV light were clearly the most effective for capturing nocturnally active mosquito species on the KU campus.