Sandamali, T. M. ChathuriGajavathany, ParththuranRajeshwaran, MeenayokiniRajakaruna, Rupika S.Perera, Piyumali K.2025-12-222025-12-222024-08-29Proceedings of the Peradeniya University International Research Sessions (iPURSE) – 2024, University of Peradeniya, P 1441391-4111https://ir.lib.pdn.ac.lk/handle/20.500.14444/7292Theileriosis affects small ruminant production and causes a serious impact on the economy. The present study aimed to investigate theileriosis in Jaffna sheep, an indigenous sheep population in Jaffna, reared for meat and manure by local communities. Hundred blood samples (5 ml) were taken from the jugular vein and altogether 57 ticks were collected from sheep in three farms in the Jaffna District. A questionnaire collected information on farm management practices and demographic data of sheep (age and gender). Geimsa-stained smears were prepared at the sample sites and nested-PCR was carried out using five Theileria species: T. ovis, T. annulata T. separata, T. lestoquardi, and T. luwenshuni (Theileria sp. China 1). Primary PCR employed outer primers Thei-F1 and Thei-R1, targeting the amplification of a 1700 bp region (of 18S rRNA gene). Secondary PCR with the inner primers Thei-F2 and Thei-R2 were further specific to the 18S rRNA gene, to amplify target regions between 1417 bp- 1426 bp. Selected amplicons were subjected to bidirectional sequencing. Microscopic examination of 50 Giemsa-stained blood smears and nested-PCR revealed 38.0% and 90.9% prevalence of Theileria spp., respectively with a statistically significant difference (Z= -3.1813, p = 0.00148). The phylogenetic analysis showed that the Theileria species identified had 99.5% sequence identity to the highly virulent Theileria luwenshuni species found in Antilope cervicapra in a zoological park in India. Although T. luwenshuni was well tolerated by Jaffna sheep, they can act as reservoir hosts and challenge the health of immunocompromised animals. Four tick species were identified as Haemaphysalis bipsinosa, Rhipicephalus haemaphysaloides, Rhipicephalus linneai (formerly known as Rhipicephalus sanguineus sensu lato tropical lineage), and Hyalomma marginatum isaaci, the most prevalent being H. bispinosa (68.4%). This is the first report and molecular characterisation of Theileria luwenshuni in Sri Lanka and possible tick vectors responsible transmitting theileriosis in Jaffna sheep.en-USTheileria luwenshuniJaffna sheepsheepTick-borne HaemoparasitesSri LankaArticle