A total of 100 cattle-calves irrespective of their age, sex and breed brought to Teaching Veterinary Clinical Complex of College of Veterinary and Animal science, Bikaner for treatment were screened for Theileria annulata infection. Blood samples were collected from jugular vein aseptically in vacutainers with and without anticoagulant for genomic DNA and serum isolation, respectively. The entire isolated DNA samples were subjected to nested polymerase chain reaction (nPCR), out of which 41 samples were found positive for Theileria annulata infection. | Serum biochemical study to cattle-calves naturally infected with theileria annulata confirmed by nested polymerase chain reaction in Bikaner district of Rajasthan India