Molecular investigations on outbreaks of ovine theileriosis among sheep and goats in Haryana, India.

Abstract

During February 2020 to October 2020, four outbreaks of theileriosis in small ruminants were recorded with overall morbidity, mortality and case fatality rates of 27.95%, 17.46% and 62.5%, respectively. The disease was characterized by high fever (up to 106°F), superficial lymphadenopathy, anaemia, anorexia, lethargy, respiratory distress and death. The presence of pleomorphic intra-erythrocytic piroplasms of Theileria species in Giemsa's stained blood smears was a common finding in all the episodes. Significant haematological alterations including high total leucocyte count and low haemoglobin and packed cell volume were characteristic. Necropsy findings of the icteric liver, enlarged spleen, pulmonary oedema and abomasal ulcerations were observed in three flocks. Smear-positive blood samples from all the episodes were screened by PCR using 18S rRNA gene-specific primer sets for T. lestoquardi, T. luwenshuni, T. uilenbergi and T. ovis. T. lestoquardi which was detected in all four flocks, while there was co-infection of T. ovis in two flocks. Phylogenetic analysis revealed that T. ovis and T. lestoquardi identified in this study had 100% and ~ 99.86% homology, respectively, with the published sequences used for comparison. This is the first confirmed report of outbreaks of malignant ovine theileriosis in the Haryana state of India which caused high morbidity, mortality and case fatality among sheep and goats. Further studies on theilerioses in small ruminants are required to understand epidemiology better.