Development and validation of an enzyme-linked immunosorbent assay for the diagnosis of porcine proliferative enteropathy

The objective of this study was to develop an indirect enzyme-linked immunosorbent assay (ELISA) Using a sonicated pure Culture of Lawsonia intracellularis Lis the antigen (So-ELISA). A total of 332 serum samples, consisting of 232 experimentally Infected animals and 100 animals naturally infected with L intracellularis, were used to assess the diagnostic sensitivity. Three hundred and Fifty-five sera from uninfected animals were used to determine the diagnostic specificity. The receiver operating characteristic and mean +3 standard deviation of optical density (OD) values from uninfected animals were used for selecting cut-off points. The diagnostic accuracy Of So-ELISA was considered to be high as the area Under the curve index was 0.991 with 0.0029 standard error. The optimal cut-off for So-ELISA was set at 0.45 OD with 89.8% sensitivity and 99.4% specificity based oil a combination of good sensitivity and high specificity. No cross-reactivity wits found in sera from pigs exposed to Brachyspira pilosicoli, B. hyodysenteriae, Campylobacter mucosalis, C. jejuni, or C coli. Inter- and intracoefficient of variation of all control sera tested with So-ELISA was less than 10%. The observed agreements between So-ELISA and the immunoperoxidase monolayer assay tested with experimental challenge animals and field samples were 95.08% with 0.88 kappa and 90.65% with 0.74 kappa value, respectively. So-ELISA was able to detect the seroconversion of infected animals at 2 to 4 weeks after exposure to L. intracellularis. Based oil the validation results,, So-ELISA could be Used as all alternative serology for proliferative enteropathy diagnosis.