Reliability of the enzyme-linked immunosorbent assay (ELISA) for the serodiagnosis of Trichinella spiralis infections in conventionally raised pigs.

An enzyme innunoassay using horse radish peroxidase as teh marker enzyme for the detection of antibodies to Trichinella spiralis in pigs was described. In the enzyme-linked immunosorbent assay (ELISA) quantitation os specific antibodies is obtained by means of peroxidase labeled anti-species-immunoglobulin in antigen-coated tubes. The enzyme remaining in the tube after wasging provides a measure of the amount of specific antibodies in the serum. A crude saline extract of T. spiralis muscle larvae served as antigen. In experiments in which conventionally raised pigs intended for slaughter were infected with various numbers of T. spiralis larvae (25,000; 12,500; 5,000; 2,500; 1,500; 500; 150; 50) a positive correlation was found between initial dose of larvae administered and amount of antibodies detected by ELISA. Compared with immuno-fluorescence (IF) ELISA was more sensitive. IF yielded positive results in 11 out of 34 infected animals, whereas ELISA results were positive in 27 cases. In order to evaluate ELISA results under practical conditions extinction values os sera from both infected and non-infected conventional pigs were compared with the highest extinction value of a group of 74 negative conventional pig sera. Due to the relatively high background reaction of some of these negative sera the number of positive practical ELISA results decreased from 27 to 19 out of 34 animals. Furthermore, in 1 out of 10 non-infected animals a false positive practical ELISA result was obtained. Ways to improve the reliability of ELISA are discussed.