The light trap is an important tool to determine the presence and abundance of vectors in the field. However, no one has studied the efficiency of light traps for collecting Culicoides in Thailand. In the present study, the efficacy of four light sources was evaluated in Prachuap Khiri Khan province, Thailand. Incandescent (INCND) light, white fluorescent (WHT-FLR) light, ultraviolet fluorescent (UV-FLR) light, and UV light-emitting diode (UV-LED) light were tested using commercial traps. In total, 30,866 individuals of Culicoides species were collected from November 2020 to June 2021, of which 21,016 were trapped on site 1 and 6,731 were trapped on site 2. The two most abundant Culicoides species were C. imicola (54%) and C. oxystoma (31.2%). UV-FLR was highly effective, followed by UV-LED light, WHT-FLR light, and INCND light, respectively, for Culicoides collection. Significantly, more Culicoides species were collected in those traps baited with UV-FLR light, UV-LED light, or WHT-FLR light than for INCND light traps. Traps equipped with UV-FLR lights can be recommended to trap Culcoides biting midges for monitoring purposes.

African horse sickness (AHS) was reported as an outbreak in Thailand in 2020. Hematophagous insects from the genus Culicoides are the suspected vector responsible for AHS transmission. Horses in Hua Hin district, Prachuab Khiri Khan province, Thailand, were affected and died from AHS in 2020. However, the potential Culicoides species and its host preference blood meal in the affected areas are unknown. To investigate the potential vectors of AHS, Culicoides were collected using ultraviolet light traps placed near horse stables. Six horse farms, including five farms with AHS history and one farm without AHS history, were included in this study. Morphological and molecular identification of the Culicoides species was performed. Polymerase chain reaction (PCR) targeting the cytochrome b oxidase I (COXI) gene for confirmation of the Culicoides species, identification of the prepronociceptin (PNOC) gene for host preference blood meal, and bidirectional sequencing were conducted. Consequently, 1008 female Culicoides were collected, consisting of 708 and 300 samples captured at positions A and B at a distance of <2 and >5 m from the horse, respectively. Twelve Culicoides species identified by morphology were noted, including C. oxystoma (71.92%), C. imicola (20.44%), C. actoni (2.28%), C. flavipunctatus (1.98%), C. asiana (0.99%), C. peregrinus (0.60%), C. huffi (0.60%), C. brevitarsis (0.40%), C. innoxius (0.30%), C. histrio (0.30%), C. minimus (0.10%), and C. geminus (0.10%). The PCR detection of the Culicoides COXI gene confirmed Culicoides species in 23 DNA samples. PCR targeting the PNOC gene revealed that the Culicoides collected in this study fed on Equus caballus (86.25%), Canis lupus familiaris (6.25%), Sus scrofa (3.75%), and Homo sapiens (3.75%) for their blood meal. Human blood was identified from two samples of C. oxystoma and a sample of C. imicola. Three dominant species including C. oxystoma, C. imicola, and C. actoni that were reported in the Hua Hin area prefer to feed on horse blood. Moreover, C. oxystoma, C. imicola, and C. bravatarsis also feed on canine blood. This study revealed the species of Culicoides in Hua Hin district, Thailand, after the AHS outbreak.

African horse sickness (AHS) was reported as an outbreak in Thailand in 2020. Hematophagous arthropods, known as Culicoides, are the suspected vector responsible for AHS transmission. Horses in Hua Hin district, Prachuab Khiri Khan province, Thailand, were affected and died from AHS in 2020. However, the potential Culicoides species and its host preference blood meal in the affected areas are unknown. To investigate the potential transmitted vectors of AHS, Culicoides were collected using light traps placed near horse stables. Six horse farms including five farms with AHS history and one farm without AHS history were included in this study. Morphological and molecular identification of Culicoides species was performed. Polymerase chain reaction (PCR) targeting cytochrome b oxidase I (COXI) gene for confirmation of Culicoides species, identification of prepronociceptin (PNOC) gene for host preference blood meal, and bidirectional sequencing were conducted. Consequently, 1,008 female Culicoides were collected with 708 and 300 female Culicoides captured at positions A and B at a distance of < 2 and > 5 m from the horse, respectively. Fourteen Culicoides species identified by morphology were noted, including Culicoides oxystoma (71.92%), Culicoides imicola (20.44%), Culicoides actoni (2.28%), Culicoides flavipunctatus (1.98%), Culicoides asiana (0.99%), Culicoides peregrinus (0.60%), Culicoides huffi (0.60%), Culicoides brevitarsis (0.40%), Culicoides innoxius (0.30%), Culicoides histrio (0.30%), Culicoides minimus (0.10%), and Culicoides geminus (0.10%). PCR detection of the Culicoides COXI gene has confirmed Culicoides species in 24 of 26 DNA samples. PCR targeting PNOC gene revealed that the Culicoides collected in this study have consumed Equus caballus (86.25%), Canis lupus familiaris (6.25%), Sus scrofa (3.75%), and Homo sapiens (3.75%) for their blood meal. Human blood was identified from two samples of C. oxystoma and a sample of C. imicola. Three dominant species including C. oxystoma, C. actoni, and C. imicola were reported in the Hua Hin area to prefer consuming horse blood. Moreover, C. oxystoma, C. imicola, and C. bravatarsis have consumed canine blood. This study revealed the species of Culicoides, the potential vector that has possibly transmitted AHS in Hua Hin district, Thailand during the outbreak.

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