Tick-borne diseases (TBDs) affect health status of beef cattle in Thailand. TBDs mostly found
in beef cattle are anaplasmosis, theileriosis and trypanosomiasis. In this study, we determined the
prevalence of TBDs for beef cattle in highland Chiang Mai, Thailand using multiplex polymerase chain
reaction (mPCR) developed in our laboratory. Data were divided into two groups based on the availability
of veterinary service in the distance of 10-30 kilometers. A total of 213 and 89 blood samples were
collected from beef cattle in highland where veterinary service is absent or present, respectively. Native
cattle of the former group were singly infected with Anaplasma marginale (13.62%), Theileria sp. (19.72%),
and co-infected with A. marginale+Theileria sp. (57.75%). Native cattle from the latter group were singly
infected with A. marginale (15.73%), Theileria sp. (17.98%), and co-infected with A. marginale+Theileria sp.
(47.19%). Our findings suggest that Theileria sp. infection is highly prevalent in native cattle in highland
Chiang Mai, followed by A. marginale infection. No Trypanosoma evansi infection was detected in either
group. Most native cattle were co-infected with A. marginale and Theileria sp. The presence of veterinary
service seemed not to affect the prevalence of blood parasite infection.