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

Abstract

The objective of this study was to develop an indirect enzyme-linked immunosorbent assay (ELISA) using a sonicated pure culture of Lawsonia intracellularis as 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 on a combination of good sensitivity and high specificity. No cross-reactivity was 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 on the validation results, So-ELISA could be used as an alternative serology for proliferative enteropathy diagnosis.

Evaluation of a blocking ELISA for the detection of antibodies against Lawsonia intracellularis in pig sera

“…To assess the performance of a new method, the diagnostic sensitivity (DSn) and specificity (DSp) should be determined in reference samples with known history and infection status [8,9,22]. However, these samples may not reflect the actual population for which the methods are intended and thus, the accuracy of the test might vary.…”

“…Several other methods are reported to have a good performance with high DSn and DSp [8,9,22]. However, these methods use various gold standards and target populations and the results given in previous papers are therefore not possible to use for comparison.…”

Management of equine proliferative enteropathy

“…In piglets, large group size, weaning, transportation, diet change and mixing have been associated with an increased susceptibility to clinical disease (Wattanaphansak and others 2008). Predisposing factors such as the stress of weaning, parasitism and underlying diseases have been suggested in the development of EPE in foals.…”

Flotation—A New Method to Circumvent PCR Inhibitors in the Diagnosis ofLawsonia intracellularis

“…Further, serological methods are cheap, fast, and easy to handle and are used to scan large numbers of samples. However, a causal relationship will not be established and false reactions may be difficult to interpret [5–7]. Identification of specific DNA by polymerase chain reaction (PCR) and immunohistochemistry (IHC) on tissue samples have been suggested as “gold standard” [8, 9].…”