# Molecular Evidence of Ovine Theileriosis in Selected Areas of Qinghai Province

## TL;DR

This study identifies high infection rates and genetic diversity of Theileria parasites in sheep from Qinghai Province, China, offering insights for disease control.

## Contribution

The study provides the first comprehensive molecular analysis of Theileria species in Qinghai Province, revealing high infection rates and genetic diversity.

## Key findings

- A 39.92% overall infection rate of Theileria species was found in Qinghai sheep.
- Three dominant Theileria species were identified, with frequent co-infections observed.
- Phylogenetic analysis showed local strains are closely related to those in other Chinese and Turkish regions.

## Abstract

This study investigates the diversity and epidemiology of Theileria species that infect sheep in Qinghai Province, China. Through molecular detection and genetic analysis, a high overall infection rate (39.92%) was found, with three dominant species identified: Theileria uilenbergi, Theileria luwenshuni, and Theileria ovis. Co-infections were frequent (22.69%), reflecting complex transmission patterns in the region. Phylogenetic analysis further revealed that local strains were closely related to those from other areas of China and from Turkey, suggesting possible historical pathogen dispersal. These findings provide key insights into the genetic structure and distribution of Theileria parasites in Qinghai, supporting improved surveillance and control strategies for ovine theileriosis.

Ovine theileriosis is a tick-borne hemoparasitic disease caused by protozoan parasites of the genus Theileria, which poses a substantial threat to sheep and goats. The disease is prevalent in northwestern China, yet studies on the diversity of its pathogens in Qinghai Province remain limited. From 2014 to 2025, 1062 blood samples were collected from sheep in 11 counties of Qinghai Province, and the Theileria spp. were investigated by PCR targeting the 18S rRNA gene. Genetic diversity analysis was performed to assess sequence variations and phylogenetic relationships. The results show that 424 samples tested positive for Theileria spp., with an overall infection rate of 39.92%, including T. uilenbergi 26.74%, T. luwenshuni 22.41%, T. ovis 18.17%, T. capreoli 0.56%, and Theileria sp. OT3 0.09%. The co-infection rate was 22.69%. Six haplotypes were detected in both T. uilenbergi and T. ovis, and fifteen in T. luwenshuni. Hap 1 was the dominant haplotype for all three species, with respective proportions of 73.08%, 77.06% and 82.17%. Phylogenetic analysis showed the strains were most closely related to those from Hunan, Turkey, Shaanxi, etc. These findings reveal a high diversity of Theileria species in Qinghai sheep, which provides crucial epidemiological insights into the transmission dynamics of ovine theileriosis in Qinghai and vital support for developing effective control strategies.