The current status of bluetongue (BT) in Thailand remains unclear, and the serotypes of BT virus (BTV) have not been determined. This study aimed to 1) investigate the epidemiology of BTV infection among goat populations in central and western Thailand
2) evaluate the test performance of conventional RT-PCR for BTV detection
and 3) identify the BTV serotypes presently circulating in the study area. The herd seroprevalence was 94.6 % (53/56, 95 % CI = 85.3-98.1), while the individual seroprevalence was 74.4 % (434/583, 95 % CI = 70.5-77.6). The odds of BTV infection were higher in goats in the western region (aOR = 10.16, 95 % CI = 5.02-20.55), with the presence of nearby ruminant farms (aOR = 2.21, 95 % CI = 1.23-4.00), and aged ≥3 years (aOR = 14.02, 95 % CI = 6.32-31.08) but lower in goats with an intensive rearing system (aOR = 0.18, 95 % CI = 0.09-0.39). For BTV detection, conventional RT-PCR presented 84.5 % sensitivity and 97.4 % specificity with an AUC of 0.910 (95 % CI = 0.852-0.967). Seven BTV serotypes (2, 3, 4, 7, 12, 16, and 21) were identified. Among these, BTV-2, 12, and 21 were the most prevalent, and BTV-4 was first detected in Southeast Asia. These results illustrated that BT is endemic and spreading widely among goat populations in the study area. Conventional RT-PCR developed in this study proved to be a reliable method for BTV detection. This research provides the first report of BTV serotype distribution in Thailand.