Tissue Fluid Enzyme-Linked Immunosorbant Assay for Piglets Experimentally Infected with Toxoplasma gondii and Survey on Local and Imported Pork in Korean Retail Meat Markets

Abstract

To investigate the prevalence of Toxoplasma gondii in pork on the market in Korea, an in-house enzyme-linked immunosorbent assay for tissue fluid (CAU-tf-ELISA) was developed using a soluble extract of T. gondii RH strain tachyzoites. As the standard positive controls, the piglets were experimentally infected with T. gondii: Group A (1,000 cysts-containing bradyzoites), Group B (500 cysts-containing bradyzoites) and Group C (1.0×103 or 1.0×104 tachyzoites). The CAU-tf-ELISA demonstrated infection intensity-dependent positivity toward tissue fluids with average cut-off value 0.15: 100% for Group A, 93.8% for Group B and 40.6% for Group C. When tissue-specific cut-off values 0.066–0.199 were applied, CAU-tf-ELISA showed 96.7% sensitivity, 100% specificity, 100% positive and 90.0% negative predictive values. When compared with the same tissue fluids, performance of CAU-tf-ELISA was better than that of a commercial ELISA kit. Of the 583 Korea domestic pork samples tested, anti-T. gondii antibodies were detected from 9.1% of whole samples and 37.9% from skirt meat highest among pork parts. In the 386 imported frozen pork samples, 1.8% (skirt meat and shoulder blade) were positive for anti-T. gondii antibodies. In Korea, prevalence of anti-T. gondii antibodies in the pork on retail markets appeared high, suggesting that regulations on pig farming and facilities are necessary to supply safe pork on the tables.

Descriptive Comparison of ELISAs for the Detection of Toxoplasma gondii Antibodies in Animals: A Systematic Review

“…Out of the 20 animal species covered, most of the studies (91%) focused on domesticated animals [ 33 , 37 , 46 , 47 , 48 , 49 , 50 ], but 7% were on zoo and wild animals [ 28 , 44 , 51 , 52 ], and one study targeted both domestic and wild animals [ 43 ]. Serum was the most widely used (89% of studies) sample for the detection of T. gondii -specific antibodies in animals, followed by meat juice/tissue fluid (7%) [ 37 , 45 , 53 , 54 ] and milk (4%) [ 55 , 56 ]. Most of the studies applied an indirect ELISA (95% of studies) [ 35 , 43 , 44 , 57 , 58 ] as the primary technique, with a smaller number using competitive ELISAs (3%) [ 59 , 60 ] or a combination of different methods (2%) (indirect IgG and IgM, blocking ELISA, reverse IgM capture ELISA) [ 29 ].…”

“…However, the same ELISA kit reported a better sensitivity (88.6%) in another study using meat juice [ 45 ]. In-house ELISAs reported higher sensitivity and specificity values of 96.7% and 100%, respectively [ 54 ].…”