The International Commission on Trichinellosis (ICT) and the World Organization for Animal Health (WOAH) recommend the use of an indirect enzyme-linked immunosorbent assay (ELISA) that utilizes excretory-secretory ( E -S) antigens (ESA) of Trichinella spiralis for surveillance and epidemiological studies in pigs and wild boars. Our efforts to optimize and standardize ESA production and ELISA protocols resulted in improved diagnostic performance of an in-house E -S ELISA. To validate the optimized assay, we compared its performance with that of a commercial E -S ELISA kit using sera from a representative set of commercial Canadian pigs (presumably Trichinella -free) and pigs experimentally infected with Trichinella spp. Both assays correctly identified the positive and negative sera, yielding 100% diagnostic sensitivity and specificity. However, in-house E -S ELISA exhibited a higher resolving power, as evidenced by the markedly better separation of normalized absorbance values of positive sera from those of samples from the negative pig population. Furthermore, significantly higher serial dilutions of sera from pigs experimentally infected with T. spiralis , T. pseudospiralis , T. britovi and T. nativa tested positive by the in-house E -S ELISA, demonstrating a higher analytical sensitivity of this assay. We continued testing sera from Canadian commercial pigs using the in-house assay to obtain a more accurate estimate of its diagnostic specificity. A total of 6345 animals have been tested, with only 11 samples showing test values above the cut-off. Ten of these sera tested negative by confirmatory western blot (WB). Therefore, the diagnostic specificity of in-house E -S ELISA alone and in combination with WB testing was 99.84% and 99.98%, respectively. WB detected seroconversion earlier than the optimized E -S ELISA in five of 15 pigs experimentally infected with various low doses of T. spiralis . The results of this study support the use of the optimized E -S ELISA and confirmatory WB for epidemiological surveys to monitor exposure to Trichinella spp. in swine.
Lobanov et al. (Sun,) studied this question.