Prevalence and molecular epidemiology of the novel equine parasite Theileria haneyi in China.

Background: Equine piroplasmosis (EP), caused by Theileria equi (T. equi) and Babesia caballi (B. caballi), is a tick-borne disease with significant economic impacts on the equine industry. Theileria haneyi (T. haneyi), a newly identified pathogen of EP, is globally distributed but has not been reported in China, where its epidemiological patterns remain undefined.

Objectives: To develop diagnostic techniques for T. haneyi and to assess its prevalence and risk factors in China.

Study design: Assay development and cross sectional survey.

Methods: A nested PCR (nPCR) nucleic acid diagnostic technique targeting the chromosome 1 single-copy (chr1sco) open reading frame (ORF) was developed. This method was applied to 1318 equine nucleic acid samples. Additionally, an iELISA serological diagnostic method was established based on the EMA11 gene. This method was utilised in a cross-sectional analysis of 2627 equine samples. Logistic regression analysis was performed to identify significant risk factors.

Results: The nPCR assay showed an 11.76% positive detection rate, while iELISA indicated a 16.41% seroprevalence. Both assays were successfully applied for the epidemiological investigation of T. haneyi. Logistic regression analysis identified host species, age, altitude, soil type, and forest and grassland coverage as the main risk factors influencing seropositivity. Phylogenetic analysis of 18S rRNA from 29 positive samples confirmed the presence of T. haneyi in China.

Main limitations: Data on clinical signs were not collected. The logistic regression model's performance metrics were not calculated.

Conclusions: This study provides the first evidence of T. haneyi infection in China and establishes a scientific basis for understanding its prevalence and geographical distribution.