Rapid and sensitive detection of Theileria equi using a novel integrated RPACRISPR/Cas13a lateral flow assay.

Abstract

BACKGROUND: Equine piroplasmosis (EP), caused by the intracellular protozoa Theileria equi, Babesia caballi, and Theileria haneyi, represents a major health and economic threat to the equine industry worldwide. Existing diagnostic methods, including PCR, serology, and microscopy, are constrained by their dependence on specialized equipment, lengthy protocols, and the requirement for skilled personnel. AIM: This study aimed to develop a rapid, accurate, and field-deployable molecular diagnostic assay for T. equi. METHODS: A nucleic acid-based diagnostic platform combining recombinase polymerase amplification (RPA) with CRISPR/Cas13-mediated detection and lateral flow device (LFD) readout was developed. The assay targets a conserved region of the erythrocyte merozoite antigen 1 (EMA-1) gene of T. equi. Validation was performed using 22 blood samples collected from horses, as well as specificity controls including B. caballi- and Anaplasma phagocytophilum-infected samples, synthetic EMA-1 DNA, and non-template controls. All assay steps were conducted at room temperature. RESULTS: The integrated RPA-CRISPR/Cas13-LFD assay generated clear visual results within 50 minutes. It demonstrated complete specificity with no false positives across all tested samples. The method effectively differentiated horses infected with T. equi, including both clinically affected and asymptomatic individuals, from healthy, uninfected animals, confirming its high accuracy and reliability. CONCLUSION: The developed assay provides a rapid, precise, and equipment-free diagnostic platform suitable for both field and clinical environments. Although the current protocol relies on DNA extraction, future optimization will aim to enable direct detection from unprocessed blood samples, thereby further simplifying point-of-care diagnostics for equine piroplasmosis.