Tick-borne pathogens can cause serious problems in grazing cattle. However, little information is available on tick-mediated diseases in cattle grazing on mountains. Thus, this study aimed to understand the potential problems related to tick-borne diseases in grazing cattle through the investigation of prevalent tick-transmitted infections, and their associated hematological changes, in terms of season and grazing type in Korean indigenous cattle (=Hanwoo). Hanwoo cattle from 3 regions of the Republic of Korea (=Korea) were either maintained indoors or placed on grassy mountains from spring to fall of 2014 and 2015. Cattle that grazed in mountainous areas showed a greater prevalence of tick-borne infections with an increased Theileria orientalis infection rate (54.7%) compared to that in non-grazing cattle (16.3%) ( P <0.001). Accordingly, the red blood cell (RBC) count and hematocrit (HCT) values of grazing cattle were significantly lower than those of non-grazing cattle throughout the season ( P <0.05). Moreover, RBC, hemoglobin (Hb), and HCT of T. orientalis -positive group were significantly lower than those of T. orientalis -negative group ( P <0.05). T. orientalis is a widespread tick-borne pathogen in Korea. Grazing of cattle in mountainous areas is closely associated with an increase in T. orientalis infection (RR=3.4, P <0.001), and with consequent decreases in RBC count and HCT. Thus, these findings suggest that the Hanwoo cattle in mountainous areas of Korea are at a high risk of infection by T. orientalis , which can lead to hematological alterations. This study highlights the necessity of preventive strategies that target T. orientalis infection.

Diarrhea is reported as one of the most common diseases in calves. It is thought to be a major cause of productivity and economic loss to cattle producers. The aim of this study is to provide a better understanding of well-known diarrheagenic pathogens and incidence of diarrhea in Korean calves. In this study, the relationship of calf diarrhea and pathogens were investigated from calves under 60 days of age in five areas of Korea from April to July, 2016. Of examined fecal samples, 38.3% was positive for any pathogens, and Giardia was the most common pathogen (25.5%). The incidence of diarrhea was 31% from pathogen-negative fecal samples whereas 61.1% from pathogen-positive fecal samples, suggesting high correlation between pathogenic factor and diarrhea. In addition, 80% of E. coli (K99) positive calves showed diarrhea, suggesting E. coli (K99) could be highly pathogenic. The incidence of diarrhea and infection rate increased with age. Rotavirus was revealed as a major pathogen in calves under 20 days of age, and the infection rate of Giardia increased rapidly in calves 20 to 39 days of age. The information on interconnections between clinical diarrhea and pathogens would contribute to developing strategies for treatment of calf diarrhea.

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