Rapid and specific detection of Babesia vogeli using RPA/CRISPR-Cas12a: A feasible field-friendly diagnostic for canine babesiosis.

Babesia vogeli is a protozoan parasite causing canine babesiosis, a tick-borne disease prevalent in tropical and subtropical regions. Its microscopic identification is challenging due to morphological similarity with other Babesia spp., and serological assays often yield inaccurate results. To address this issue, we developed a rapid, equipment-minimal diagnostic method combining recombinase polymerase amplification (RPA) with CRISPR/Cas12a (RPA/CRISPR-cas12a) for B. vogeli-specific detection. The RPA assay enables DNA amplification for both B. vogeli and Hepatozoon canis, while CRISPR/Cas12a using gRNA_Bab ensures specificity for B. vogeli, even in co-infections and other pathogens. This approach detects as few as 10⁵ copies within two hours for both readout platforms such as fluorescence and lateral flow dipstick (LFD). Forty canine blood samples were detected by RPA/CRISPR-cas12a to examine its performance. Results showed high concordance with qPCR-high resolution melting (HRM) (Cohen's kappa: 0.93 for fluorescence, 0.81 for LFD), outperforming conventional PCR. The clinical sensitivity and specificity of RPA/CRISPR-cas12a were 100 % and 96.8 %, respectively and the concordance with qPCR-HRM was 97.5 %. RPA/CRISPR-cas12a for Babesia spp. detection provided a simple, rapid, and accurate method, demonstrating promise for point-of-care diagnosis of canine babesiosis in resource-limited settings. This method showed high potential as a practical diagnostic tool in veterinary clinics, with accelerated surveillance to control outbreaks of Babesia-associated canine babesiosis.