Abstract
Theileria and Babesia are emerging threats to wildlife health but remain underreported in captive large herbivores. This study aimed to investigate the presence and genetic identity of Theileria and Babesia in large captive herbivores in Thailand using PCR targeting the 18 S rRNA gene. Blood samples were collected from 31 individuals representing five herbivore species: Malayan tapirs (Tapirus indicus), white rhinoceroses (Ceratotherium simum), pygmy hippopotamuses (Choeropsis liberiensis), bantengs (Bos javanicus), and gaurs (Bos gaurus) across five zoological parks in central Thailand. A total of 16 positive samples were identified, including one coinfection, resulting in an overall infection rate of 51.6% (16/31; 95% CI: 33.1-69.9). Theileria equi-like was detected in 37.5% (3/8; 95% CI: 8.5-75.5) of Malayan tapirs. Theileria bicornis was detected in 75% (9/12; 95% CI: 42.8-94.5) of white rhinoceroses. In gaur, the infection rate was 33.3% (4/12; 95% CI: 9.9-65.1), comprising one Babesia ovata infection, two Theileria orientalis, and one coinfection. This study provided the first molecular confirmation of Babesia ovata infection in gaurs. No infections were detected in pygmy hippopotamuses or bantengs. These results provide novel baseline data on tick-borne pathogens in captive environments, highlighting potential risks to susceptible wildlife, both non-domestic and domestic species, and underscoring implications for conservation. Our findings emphasize the need for continued surveillance, integrated vector management, and targeted control strategies in zoological settings to mitigate pathogen transmission and protect animal health.