Development of a SAG1-based Colloidal Gold Immunochromatographic Strip for Rapid Serological Detection of Swine Toxoplasma gondii

Background Toxoplasmosis, a globally prevalent zoonosis caused by Toxoplasma gondii ( T. gondii ), infects nearly all warm-blooded animals, including humans, cats and pigs. Beyond incurring substantial economic losses, T. gondii infection poses a severe threat to public health, as pigs, which are key intermediate hosts for T. gondii transmission, serve as major source of human infection via the food chain. Thus, developing specific, sensitive, rapid, and easy-to-perform detection methods for porcine T. gondii is of paramount importance for the prevention, control, and eventual eradication of this pathogen in swine populations. Methods To address this need, a novel colloidal gold immunochromatographic strip (CGIS) for the rapid serological detection of T. gondii infection in swine was developed in this study. The strip was constructed using recombinant surface antigen 1 (SAG1) expressed in a baculovirus-insect cell system, which ensures the protein retains native antigenic epitopes. The purified SAG1 protein was conjugated to colloidal gold nanoparticles and loaded onto a conjugate pad, while staphylococcal protein A (SPA) and a polyclonal anti-SAG1 antibody were immobilized on a nitrocellulose (NC) membrane to form the test line (T line) and control lines (C line), respectively. Results Clinical validation demonstrated that the developed CGIS exhibits high specificity, with no cross-reactivity to sera positive for 16 common porcine pathogens, superior sensitivity that is 32-fold greater than that of a commercial enzyme-linked immunosorbent assay (ELISA) kit. Importantly, the strip showed high reliability with detection results demonstrating 96.07% concordance with the reference microscopic agglutination test (MAT). Conclusions In conclusion, this SAG1-based CGIS provides a powerful, user-friendly tool for large-scale surveillance and on-farm screening of porcine toxoplasmosis, which is crucial for supporting T. gondii control in pigs.