A clinical case of bovine anemia due to Theileria orientalis group in a non-grazed dairy cow in the upper part of South Korea

This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial license (http://creativecommons. org/licenses/by-nc/4.0/), which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Bovine anemia due to Theileria orientalis group (BATOG) is a tick-borne disease (TBD) affecting cattle, with Haemaphysalis spp. as the major tick involved in disease transmission [1]. Unlike the lymphoproliferative Theileria species, BATOG mainly affects the erythrocytes (RBC) and RBC-associated parameters [2]. Clinical signs include weakness, abortion, fever, pallor, and elevated respiratory and heart rates [2]. However, few clinical cases of T. orientalis infection in cattle have been reported. Consequently, T. orientalis was historically considered to cause benign infection only [2]. Despite the minimal pathogenic effects of BATOG to the cattle, significant losses have been associated due to increased treatment costs, and reduced body weight, production, and reproductive performance, and ultimately, poor welfare and death [2]. BATOG is also known as ‘oriental theileriosis’ because the main vector, Asian long-horned tick, was previously thought to be endemic in East-Asian countries only. But in the past decade, outbreaks of BATOG have been reported in many countries, including several Asian and Asia-Pacific countries [2], and recently the United States [3]. T. orientalis is categorized onto 11 genotypes, with Chitose and Ikeda as genotypes that could lead to reduced health status in cattle [4]. In South Korea, above 95% of cattle farm are operating under non-grazed management. It is favorable for the dairy farmers as it can control outdoor conditions, reduce tick exposure, and enhance the milk yield volume and composition. In South Korea, the most studied bovine TBD was BATOG, as previous reports revealed that it has the highest prevalence compared to anaplasmosis, rickettsiosis, This study reports the detection and genotyping of the first clinical case of bovine anemia due to Theileria orientalis group (BATOG) in non-grazed dairy cow in upper South Korea. Blood and serum tests revealed anemia and hyperbilirubinemia from animal showing clinical symptoms, and later confirmed as piroplasmosis-positive. Follow-up surveillance on the herd revealed 2 asymptomatic cows with anemia. The three animals were confirmed theileriosis-positive and genotyping revealed the clinical and one of the asymptomatic cases have Chitose, while the other has Ikeda genotype. Clinical BATOG cases were rarely reported worldwide, and asymptomatic animals left untreated could serve as parasite reservoir.