Nucleic acid-based diagnosis of Babesia bigemina infection in bovines of Telangana state, India

Bovine babesiosis due to Babesia bigemina is a tick-borne intra-erythrocytic haemoprotozoan parasite causing substantial economic losses to the global livestock sector in temperate to tropical countries.The clinical signs of the acute disease include pyrexia, anorexia, depression, weakness, ataxia, hemoglobinuria, anemia, jaundice, and the presence of intra-erythrocytic parasites [1,2].The recovered animals become carriers of the infection for both ticks and naive cattle [3,4].Diagnostic techniques like microscopy, Quantitative Buffy Coat (QBC) analysis, and several serological methods such as Complement Fixation Test (CFT), ABSTRACT: Bovine babesiosis due to Babesia bigemina, is an intra-erythrocytic, tick-borne protozoan disease affecting bovines.The recovered animals from acute infection remain carriers of these blood parasites posing a potential threat of infection to healthy, susceptible populations.A total of 158 whole blood samples each along with blood smears were collected from the bovines in different districts of Telangana for PCR assay and blood smear examination, respectively.PCR assay targeting the 18S rRNA gene of Babesia sp. and SpeI-AvaI restriction fragment of B. bigemina were conducted and compared with conventional blood smear examination for its efficacy in the diagnosis of babesiosis.PCR amplified the B. bigemina DNA with a sensitivity of 625 pg and could detect the pathogen in 16 out of 158 blood samples indicating a prevalence rate of 10.12%.The prevalence of babesiosis exhibited a significant increase (p=0.029) in correlation with the age of the animals.The infection rate was notably higher in animals aged 2-5 years (17.14%),followed by those older than 5 years (6%), compared to the younger animals below two years (2.63%) of age.Moreover, the occurrence of babesiosis was significantly higher (p=0.043)among crossbred animals (13.72%) in comparison to indigenous breeds (3.57%).Additionally, a distinct genderbased difference was observed, with females (13.27%) showing a significantly higher incidence (p=0.038)compared to males (2.22%).Giemsa-stained blood smear examination detected piroplasms in only 5 out of 158 blood smears screened indicating a prevalence rate of 3.16%.Hence, considering the superiority of PCR assay over conventional microscopic techniques, the test is recommended for the field diagnosis of bovine babesiosis.