Evaluation of three ELISA assays for detection of Mycobacterium avium subsp. paratuberculosis antibodies in serum of sika deer (Cervus nippon).

ELISA-based assay testing offers a practical, high-throughput approach for early detection of Mycobacterium avium subsp. paratuberculosis (MAP), the causative agent of Johne's disease (JD), particularly for identifying subclinically infected animals within a herd. As no ELISA has been developed specifically for sika deer, the aim of this study was to compare the diagnostic performance of two commercial ELISA assays (ID.VET and IDEXX) designed for cattle, sheep and goats, and the Paralisa™ assay developed for red deer. Serum and faecal samples (n = 105) were collected from 36 clinically affected sika deer at postmortem, 40 apparently healthy sika deer from the same infected herd at slaughter, and 29 sika deer from a JD-free herd at postmortem. Individual liquid faecal culture confirmed infection and MAP shedding status, with 73 animals (69.5%) testing culture positive. Sensitivities were 48% (Paralisa™), 43% (ID.VET) and 4% (IDEXX), while all assays showed 100% specificity. Paralisa™ and ID.VET assays demonstrated almost perfect agreement (κ = 0.86), whereas the IDEXX assay showed poor agreement with both assays. ID.VET assay also showed excellent inter-laboratory repeatability (ICC = 0.93). Overall, Paralisa™ and ID.VET assays provided superior sensitivity for MAP antibody detection in sika deer and may aid JD monitoring in infected herds.