Seasonal changes in hemograms and Theileria orientalis infection rates among Holstein cattle pastured in the mountains in the Republic of Korea.
In the current study, we compared seasonal changes in complete blood counts (CBCs) and rates of infection with a tick-borne pathogen between Holstein cattle housed indoors and those maintained outside on pasture. There were differences in white blood cell (WBC) parameters, but the changes were not associated with seasons or the housing type. Analysis of red blood cell (RBC) parameters showed lower values in August and November versus March, and in the cattle maintained on pasture versus the housed cattle. In comparison with the RBC count of the housed cattle in March (10.1M/μL), the RBC counts of the pastured cattle were significantly lower in August (7.8M/μL; p<0.01) and November (7.5M/μL; p<0.01). The hematocrit (HCT) also showed a decrease in March (33.5%), August (30.0%, p<0.01) and November (28.5%, p<0.01). According to PCR analysis, the Theileria infection rate among the pastured cattle in March was only 11%, but this rate increased to 22% and 60% in August and November, respectively. The RBC count (7.4M/μL) and HCT (27.7%) values in Theileria-positive pastured cattle in November showed a dramatic decrease compared to those of cattle examined in March. Phylogenetic analysis revealed that these Theileria isolates correspond to T. orientalis. These results suggest that a remarkable increase in tick infestation in mountainous areas in the summer may cause increased rates of infection with T. orientalis, leading to significant changes in the RBC profile after grazing. Therefore, these hematological changes may be associated with T. orientalis infection caused by tick-biting; thus, additional studies on the pathogenicity of T. orientalis are needed.
College of Ecology and Environmental Science, Kyungpook National University, Sangju 37224, Republic of Korea. Electronic address: jpark@jbnu.ac.kr.
Kyoung-Seong
KS
Choi
College of Veterinary Medicine, Chonnam National University, Gwangju 61186, Republic of Korea.
Do-Hyeon
DH
Yu
Laboratory of Veterinary Internal Medicine, BK21 PLUS Program for Creative Veterinary Science Research, Research Institute for Veterinary Science and College of Veterinary Medicine, Seoul National University, Seoul 08826, Republic of Korea.
Joon-Seok
JS
Chae
College of Veterinary Medicine, Chungnam National University, Daejeon 34134, Republic of Korea.
Bae-Keun
BK
Park
Laboratory of Veterinary Clinics, National Institute of Animal Science Rural Development Administration, Jeonju 54875, Republic of Korea.
Jae-Gyu
JG
Yoo
College of Veterinary Medicine, Chonbuk National University, Iksan 54596, Republic of Korea.
Jinho
J
Park
D000818:Animals; D001772:Blood Cell Count / Q000662:veterinary; D002417:Cattle; D005260:Female; D056910:Republic of Korea / Q000453:epidemiology; D012621:Seasons; D016794:Theileria / Q000302:isolation & purification*; D013801:Theileriasis / Q000453:epidemiology* / Q000469:parasitology
Complete blood counts; Holstein cattle; Mountainous areas; Pasture; Theileria orientalis; Tick-borne pathogen