Actinobacillus pleuropneumoniae (APP) is a significant respiratory pathogen of swine, causing acute death in finishing pigs and adding significant treatment costs to the production of clinically-affected pigs. Several factors are involved in the pathogenesis of APP, including capsular polysaccharides, mural lipopolysaccharides, and proteinaceous exotoxins. There are four recognized APP toxins, but only ApxIV is specific to APP and expressed by all serotypes1. For this reason, the detection of anti-ApxIV serum antibodies has been used to identify APP infections.

Our research group has previously developed antibody ELISAs capable of detecting antibody against PRRSV, influenza A virus, and African swine fever virus in swine oral fluids. The efficiency of this approach has sparked commercial interest, i.e., 3 commercial diagnostic companies currently produce diagnostic tests for the detection of PRRSV antibody in oral fluids. Consistent with our experience with previous antibody assays, we found that we could develop an ELISA capable of detecting antibody against ApxIV in oral fluid specimens.