Abstract
BackgroundLawsonia intracellularis is a common cause of chronic diarrhoea and poor performance in young growing pigs. Diagnosis of this obligate intracellular bacterium is based on the demonstration of the microbe or microbial DNA in tissue specimens or faecal samples, or the demonstration of L. intracellularis-specific antibodies in sera. The aim of the present study was to evaluate a blocking ELISA in the detection of serum antibodies to L. intracellularis, by comparison to the previously widely used immunofluorescent antibody test (IFAT).MethodsSera were collected from 176 pigs aged 8-12 weeks originating from 24 herds with or without problems with diarrhoea and poor performance in young growing pigs. Sera were analyzed by the blocking ELISA and by IFAT. Bayesian modelling techniques were used to account for the absence of a gold standard test and the results of the blocking ELISA was modelled against the IFAT test with a "2 dependent tests, 2 populations, no gold standard" model.ResultsAt the finally selected cut-off value of percent inhibition (PI) 35, the diagnostic sensitivity of the blocking ELISA was 72% and the diagnostic specificity was 93%. The positive predictive value was 0.82 and the negative predictive value was 0.89, at the observed prevalence of 33.5%.ConclusionThe sensitivity and specificity as evaluated by Bayesian statistic techniques differed from that previously reported. Properties of diagnostic tests may well vary between countries, laboratories and among populations of animals. In the absence of a true gold standard, the importance of validating new methods by appropriate statistical methods and with respect to the target population must be emphasized.
Highlights
Lawsonia intracellularis is a common cause of chronic diarrhoea and poor performance in young growing pigs [1,2]
Cultivation of this obligate intracellular bacterium is difficult and the diagnosis is based on demonstration of the microbe or microbial DNA in tissue specimens or faecal samples by techniques such as PCR [4]
Herds and animals In study A, L. intracellularis DNA was demonstrated by PCR in 29 of 54 animals from the poor performance herds
Summary
Lawsonia intracellularis is a common cause of chronic diarrhoea and poor performance in young growing pigs Diagnosis of this obligate intracellular bacterium is based on the demonstration of the microbe or microbial DNA in tissue specimens or faecal samples, or the demonstration of L. intracellularis-specific antibodies in sera. The first method commercially available was an immunofluorescent antibody test, IFAT [5], with a stated sensitivity of 91% and specificity of 97% (Elanco Animal Health Indianapolis, Indiana, USA) This widely used method is based on the incubation of sera with semipurified L. intracellularis antigen, and the results are visualised following incubation with anti-porcine fluorescein isothiocyanate conjugate. The latter method is only commercially available to a limited extent
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
