Tick-borne Pathogen Detection and Its Association with Alterations in Packed Cell Volume of Dairy Cattle in Thailand

SIMPLE SUMMARY: Tick-borne diseases adversely impact bovine health, leading to huge financial losses for farmers. Timely and accurate disease diagnosis is key in managing bovine herds, particularly in production animals such as dairy cattle. In the present study, we molecularly detected tick-borne pathogens (TBPs) in dairy cattle from selected provinces in the northern and western parts of Thailand. Specifically, common TBP infection was widespread in the sampled animals. Two detection tools were also compared for pathogen detection. Furthermore, cattle positive for tick-borne infections had notably lower hematocrit values. The results of this study emphasize the importance of regular tick-borne surveillance and its possible clinical impact on economically important dairy cattle in Thailand. ABSTRACT: Tick-borne diseases (TBDs) massively impact bovine production. In endemic countries, animals are often subclinically infected, showing no signs of the illness. Anemia is a hallmark of TBDs, but there is inadequate information on its presence in infected Thai cattle. In the present study, 265 cattle from four provinces in Thailand were surveyed to identify tick-borne pathogens (TBPs) and to evaluate the changes in the packed cell volume (PCV) values associated with detection. Microscopy and polymerase chain reaction (PCR) were also compared for TBP detection. Babesia/Theileria/Hepatozoon was detected in 33.58% (89/265) of the cattle samples. Specifically, Babesia bovis (9/265), B. bigemina (12/265), Theileria orientalis (62/265), and Anaplasma marginale (50/265) were identified using species-specific assays. Significant decreases in the mean PCV levels were observed in cattle that were positive for at least one TBP (p < 0.001), Babesia/Theileria/Hepatozoon (p < 0.001), T. orientalis (p < 0.001), and A. marginale (p = 0.049). The results of PCR and microscopy for the detection of TBPs suggested slight and fair agreement between the two detection tools. The present findings contribute to a better understanding of TBDs in the field and shall facilitate the formulation of effective control for TBDs in Thailand.