Abstract：Actinobacillus pleuropneumoniae (APP) is the causative agent of porcine contagious pleuropneumonia which causes great economic losses in the pig industry worldwide. There are at least 15 serotypes of APP so that it is very difficult to diagnose and control this disease. An ApxIV-ELISA which could distinguish the vaccinated pigs from APP-infected ones was established in our previous study based on the fact that the toxin ApxIV expresses only in vivo (in APP-infected pigs), but not in vitro. In this study, we developed this method a differentiating diagnostic kit, whose specificity, sensitivity, repeatability and stability were evaluated and compared with an analogous ELISA kit (CHEKIT-APP-APXIV) from the company IDEXX and the indirect haemagglutination assay (IHA). A total of 1453 clinical sera from China, UK, Denmark, USA, Canada and Australia were screened using our ApxIV-ELISA kit. The results showed that the ApxIV-ELISA kit has very high specificity、 sensitivity and repeatability [the inter- and intrabatch imprecision (CV%) < 15%] and stability (very stable at 4-8 C for 9 months). Compared with CHEKIT-APP-APXIV, the overall agreement rate was up to 91.37%. Our data confirmed that the ApxIV-ELISA kit can be used to distinguish the vaccinated pigs from APP-infected ones.
