Validation of a two-tier serological strategy using in-house ELISA and Western blotting for improved surveillance of Trichinella spiralis in swine populations.

Trichinellosis is a major zoonosis in Argentina, affecting both human health and swine production. Detection of Trichinella larvae by artificial digestion (AD) remains the reference diagnostic method. This study assessed the performance of an in-house indirect ELISA coupled with Western blotting (WB) using excretory-secretory antigens from Trichinella spiralis muscle larvae (ML) (ISS643 reference strain) as a diagnostic strategy for detecting Trichinella spp. specific antibodies in swine. Evaluated against AD in 375 serum samples, the in-house ELISA showed a relative sensitivity of 90.3% (95%CI: 75.1-96.6) and relative specificity of 98.5% (95%CI: 96.6-99.4). When ELISA-positive samples were further analysed by WB, the combined diagnostic strategy achieved 100% specificity (95%CI: 98.9-100) and 87.1% sensitivity (95% CI: 71.15-94.9). Cohen's kappa analysis for concordance with AD showed excellent agreement for the ELISA (κ = 0.863) and ELISA/WB strategy (κ = 0.925). No correlation was observed between T. spiralis larval load and antibody levels (r = -0.1264). Analysis of sera (n = 64) from experimental infections in pigs showed seroconversion as early as 14 days post-infection for high doses (10,000 ML) and 35-49 days post-infection for low doses (100 ML). The ELISA/WB combined approach effectively ruled out false positives in those pigs naturally infected with other gastrointestinal parasites (n = 14), with only one exception in a piglet. The locally developed ELISA/WB diagnostic strategy is a robust and accessible serological tool for surveillance and individual management of animals in endemic foci, potentially reducing the economic impact of trichinellosis in low-resource settings.