Comparative Evaluation of MAT, PCR, and LAMP Assays for the Diagnosis of Canine Leptospirosis

Abstract

Leptospirosis is a globally significant zoonosis in dogs, yet its clinical diagnosis remains challenging due to the heterogeneous performance of available assays. This study evaluated the diagnostic accuracy of the microscopic agglutination test (MAT), polymerase chain reaction (PCR), and loop-mediated isothermal amplification (LAMP) in dogs presenting with clinical signs suggestive of leptospirosis at the Teaching Veterinary Clinical Complex, Pookode. Among the total 52 dogs screened, 50.0% (26/50) were confirmed positive by at least one diagnostic assay. Of these, 23.1% were detected by MAT, 53.9% by PCR, and 88.5% by LAMP. MAT demonstrated 100% specificity but low sensitivity (23.1%), identifying Pomona, Icterohaemorrhagiae, and Pyrogenes as predominant serovars. PCR targeting the lipL32 gene achieved moderate sensitivity (53.9%), reflecting its value during the leptospiraemic phase but diminished reliability in later infection. The LAMP assay showed superior diagnostic performance, with 88.5% sensitivity, substantial agreement with PCR (κ = 0.63), and a highest accuracy by ROC analysis (AUC = 0.94) compared with PCR (AUC = 0.77) and MAT (AUC = 0.62). These findings underscore the limitations of MAT in acute diagnosis, while highlighting LAMP as a rapid, robust, and highly sensitive alternative suitable for clinical and field application. Integration of molecular assays, particularly LAMP, with serology offers a comprehensive diagnostic strategy across different stages of canine leptospirosis, with implications for both veterinary care and zoonotic surveillance.