First Molecular Confirmed Outbreak of Malignant Ovine Theileriosis in Sheep from North India.

Context: Malignant ovine theileriosis is a tick-borne disease of sheep and goats, caused by protozoan Theileria lestoquardi. The disease has serious economic implications for small ruminant production around the world. Methods: An outbreak of malignant ovine theileriosis in a sheep flock was investigated from Hisar district of Haryana, India, in March 2022. The etiological agent was identified using polymerase chain reaction assay with genus specific primers targeting 18S rRNA gene and subsequently confirmed by sequencing. Results: The morbidity, mortality and case fatality rate reported in the outbreak were 22.2, 18.8 and 85%, respectively. The phylogenetic analysis clustered the present study T. lestoquardi isolate in the same clade with T. lestoquardi from Iraq, Iran and Pakistan with maximum nucleotide identity of 99.37% with strains from Iraq. The tick vector Hyalomma anatolicum recovered from dead animals was implicated in the disease's transmission. Conclusions: Malignant ovine theileriosis resulted in high case fatality rate. This study presents the first molecularly confirmed outbreak of malignant ovine theileriosis outbreak in the North Indian region, with characteristic post-mortem findings. [ABSTRACT FROM AUTHOR]