Comparison between a commercial ELISA and IFAT for the detection of anti-Toxoplasma gondii antibodies on serum and meat juice of swine

Introduction - The ingestion of raw or undercooked swine meat is considered a source of Toxoplasma gondii infection in humans, due to the persistence of tissue cysts in this species. Up to date the detection of specific antibodies represents the most common approach used to monitoring the rate of T. gondii infection in swine destined for human consumption; evaluating the efficiency of immunodiagnostic methods is a great challenge for toxoplasmosis control measure. Aim - The aim of the present study was to compare a commercially ELISA with an IFAT method for detection of anti-T. gondii antibodies in naturally-infected swine, targeting two different matrices (serum and meat juice). Materials and Methods - Samples of serum and diaphragm meat juice, obtained from 280 swine at slaughter level, were tested for the detection of anti-T. gondii (IgG) antibodies by means of a commercial indirect ELISA kit "ID Screen Toxoplasmosis indirect" and an IFA assay. The results were compared to evaluate the concordances between the two different immunodiagnostic approach and also the two matrices. Results and discussion - Antibodies against T. gondii were detected in 50 (17.85%) blood samples and in 38 (13.57%) meat juices by IFAT whereas 51 (18.21%) blood samples and 40 (14.28%) meat juice samples tested positive by ELISA. The ELISA kit performed on both the matrices showed to be an easy and high reproducible method to employ (CV<10%). The ELISA kit applied on serum exhibited very good performances, with high level both of Se (90%) and Sp (97.39%) and an "almost perfect agreement" with the reference test IFAT (K=0.87). Meat juice showed good accuracy (>80%) and good correlation with the results obtained on serum using both the immunodiagnostic approach, although a statistical difference between the positive rates recovered on serum and meat juice was observed. Conclusions - The results obtained suggest that the commercial ELISA kit applied both on meat juice (an easy and constant available matrix) and serum, might be a good test for toxoplasmosis epidemiological survey on swine.