Prevalence and genetic characterization of Theileria annulata and Theileria orientalis in Post-abortion cattle.

Tropical theileriosis is a significant health risk for cattle especially in tropical and subtropical regions where it contributes to high mortality rates and economic losses. Tick-borne protozoan parasites belonging to Theileria genera are responsible for this infection. Theileriosis has been associated with abortion and stillbirth in cattle, primarily as an indirect consequence of maternal illness; however, this association has not been investigated in Pakistan. Therefore, the present study aimed to determine the molecular prevalence and distribution of Theileria species in cattle with a recent history of abortion across three districts of Punjab, Pakistan. A total of 138 blood samples were collected from cattle in Bahawalpur, Lodhran and Muzaffargarh districts during February 2024 till March 2025 having recent history of abortion. Genomic DNA of cattle was screened for the presence of Theileria spp. by targeting a fragment from their conserved 18S rRNA gene. Out of the screened samples, 56 (40.6%) tested positive for Theileria spp. and DNA sequencing confirmed the presence of T. annulata and T. orientalis in 21/138 (15%) and 1/138 (0.7%) cattle, respectively. Phylogenetic analysis revealed that sequences amplified in this study were similar to 18S rRNA gene of T. annulata and T. orientalis deposited from different countries worldwide. The highest Theileria spp. and T. annulata infection rate was recorded in Holstein-Friesian cattle (73% and 36%) followed by Sahiwal (40% and 15%), Dajal (35% and 12%) and Cholistani (32% and 12%, respectively). Age, ectoparasite infestation, grazing mode, and use of acaricides were not significantly associated with Theileria spp. infection. In conclusion, detection of Theileria spp., especially T. annulata, in a notable proportion of cattle with a history of abortion suggests a potential role in reproductive losses. Further studies are required to confirm the causal link. Additionally, regular screening, effective tick control and proper herd management are recommended to reduce the risk of infection and associated reproductive issues.