Assessment of diagnostic accuracy of a commercial ELISA for the detection of Toxoplasma gondii infection in pigs compared with IFAT, TgSAG1-ELISA and Western blot, using a Bayesian latent class approach

Abstract

Serological methods are the most commonly used diagnostic tools to detect Toxoplasma gondii infections in pigs . In the absence of a readily available ‘gold standard’, an estimation of diagnostic accuracy is dif- ficult to assess. A commercial ELISA (PrioCHECK Toxoplasma Ab porcine ELISA, Prionics, Schlieren, Switzerland) for the diagn osis of T. gondii infection in pigs was evaluated in naturally infected animals from two distinct populations; indoor and outdoor living animals. An assessment of diagnostic accuracy, using a Bayesian latent class approach with adjustm ent for within indoor and outdoor farm clust ering using random effects, was performed. Tests used for comparison were: IFAT; ELISA using native affinity-puri- fied P30 (SAG1) T. gondii tachyzo ite surface antigen (TgSAG1-ELISA); and Western blot with T. gondii tachyzoites lysate. The data set comprised 297 pig serum samples across outdoor (n = 149) and indoor (n = 148) farms in Argentina. The estimated sensitivity and specificity for the comme rcial ELISA were 98.9% (95% credible interval: 96.2; 100) and 92.7% (95% credible interval: 87.7; 96.6), respectively. The analysis of sera and plasma from pigs (n = 6) experimentally inoculated with 5,000 T. gondii oocysts revealed a pronounced antibody response beginning 2 weeks p.i. until the end of the observation period (11 weeks p.i.) in all animals. Meat juice obtained from inoculated animals after euthanasia also tested positive. These results suggest that the PrioCHECK Toxoplasma Ab porcine ELISA may be a useful tool to perform serological diagn osis of T. gondii infections in pigs to control Toxoplasma infection in pigs and humans.