Comparison of commercial ELISA tests for the detection of Toxoplasma antibodies in the meat juice of naturally infected pigs

Abstract

Toxoplasmosis is a globally distributed protozoal zoonosis. Pigs are considered an important reservoir of Toxoplasma gondii and pork a major infection source of human toxoplasmosis. ELISA methods are commonly used diagnostic tools for detecting Toxoplasma infections. They are also used for slaughterhouse-based serological monitoring of toxoplasmosis in pigs to identify positive farms. The methods used are non-standardised with varying sensitivity and specificity. In our study, four commercial ELISA tests for the detection of Toxoplasma antibodies in the meat juice of slaughter pigs were compared with a modified agglutination test (MAT) as a reference. The cut-off values of the ELISA tests provided by the manufacturer varied between 0.20 and 0.50, and clearly influenced prevalence. The sensitivity of tests I, II and III varied between 96.4 and 78.6. Sensitivity was unacceptably low (3.6) for test IV (cut-off=0.30). Tests I, II and III had the highest accuracy and the best agreement with the reference test when a cut-off of 0.30 was used. Test II and III showed very good agreement (K=0.92 and 0.84, respectively) with the MAT. A very strong correlation (Pearson correlation >0.89) was observed between the S/P values of tests I, II and III. Our results demonstrate that the test and cut-off value used influence the results of the apparent seroprevalence studies.

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

“…The in-house CAU-tf-ELISA kit manufactured using these well-designed positive controls produced better sensitivity and negative predictive values than the Commercial kit S. Different cut-off values, 0.15 for the CAU-tf-ELISA kit and 0.3 for the Commercial kit S, might have influenced the results of diagnostic performance. This is consistent with previous findings [ 35 ], in which the authors compared 4 commercial ELISA kits for detectability of anti- T. gondii antibodies in the meat fluid of slaughtered pigs using MAT as a reference. The use of cut-off values (0.07–0.50) other than the thresholds preset by the manufacturers produced the highest accuracy.…”

Liver Transudate, a Potential Alternative to Detect Anti-Hepatitis E Virus Antibodies in Pigs and Wild Boars (Sus scrofa)

“…Meat juice has also been used in some studies to determine HEV seroprevalence in hunted wild boars and slaughtered pigs with satisfactory results [48,56]. Similarly, other reports also demonstrated the utility of meat juice to determine the prevalence of different agents such as Salmonella, Trichinella, influenza virus or Toxoplasma [57,58]. Meat juice, like other body fluids, contains fewer antibodies against HEV, Toxoplasma gondii, and other pathogens than serum [56][57][58][59], so the dilution factor in serological assays should be adjusted accordingly.…”

“…Similarly, other reports also demonstrated the utility of meat juice to determine the prevalence of different agents such as Salmonella, Trichinella, influenza virus or Toxoplasma [57,58]. Meat juice, like other body fluids, contains fewer antibodies against HEV, Toxoplasma gondii, and other pathogens than serum [56][57][58][59], so the dilution factor in serological assays should be adjusted accordingly. Therefore, liver transudate was tested undiluted and at different dilutions to determine this factor.…”

Use of meat juice and blood serum with a miniaturised protein microarray assay to develop a multi-parameter IgG screening test with high sample throughput potential for slaughtering pigs

“…Nevertheless, usability of meat juice for serological analysis of pigs has already been proven in many cases for different pathogens, for example for Salmonella spp. [30], PRRSV [31], Hepatitis E virus [32] and T. gondii [33].…”