Oral fluid as a material for serological diagnostics of caseous lymphadenitis in goats

Corynebacterium pseudotuberculosis causes caseous lymphadenitis (CLA) in goats and sheep. This study assessed oral fluid (OF) as a minimally invasive sample for CLA serodiagnosis by detecting antibodies to PLD, CP40, and PknG using Western blot (WB). Ninety-six goats from a CLA-affected herd in Poland were tested. Paired serum and OF samples were analyzed via ELISA (serum only) and WB (serum and OF). The rPLD-ELISA had 70–80% diagnostic sensitivity, depending on the cut-off. WB on serum showed high sensitivity (98%) and good agreement with ELISA. WB on OF had slightly lower sensitivity (90%), with differences in antigen detection. OF shows promise for CLA diagnosis, with PLD antibodies being the most relevant. Fewer OF samples had CP40 and PknG antibodies, likely due to antibody class differences or detection limitations. Further investigation into immunoglobulin classes present in different sample types and optimized secondary antibodies is essential for developing an effective OF-based diagnostic test for CLA.