[The influence of the procedure of excretory-secretory L1 trichinella spiralis antigen preparation on the efficiency of an ELISA test in pigs]

Abstract

Background: Trichinellosis is a parasitic zoonosis transmitted to humans by consumption of raw or undercooked meat from animals infected by worms of the Trichinella genus. Every year seropositive cases are found among the human population and thus trichinellosis still remains an epidemiologically important disease in Poland. The usefulness of ELISA for anti-T. spiralis IgG detection in pigs is still limited by the nature of antigen. The objective in the present study was to compare the usefulness of excretory-secretory antigens of L1 T. spiralis for the serological detection of IgG antibodies in pigs.

Material and methods: The antigens were prepared in different laboratories: Ag ES L1 T. spiralis (N) in Germany, Ag ES L1 T. spiralis (W) in Italy and Ag ES L1 T. spiralis in Poland. Conventional, Iberian pigs were infected with 200, 1000 and 20 000 muscle larvae of T. spiralis. Serum samples were obtained at 5 and 1 dbi (day before infection), and 5, 10, 15, 20, 25, 30, 40, 50, 60 dpi (day post infection) and screened for specific IgG antibodies to excretory-secretory L1 T. spiralis antigens. Serum samples were obtained from the EU project TRICHIPORSE. The cut-off value of ELISA was determined on serum samples from 248 Trichinella-free pigs from Poznaii and Boza Wola, that were examined by artificial digestion.

Results: In pigs infected with 200 L1 T. spiralis larvae, specific IgG were detectable from 50 dpi, when the Ag ES L1 T. spiralis (N) was used, whereas when Ag ES L1 T. spiralis (W) and Ag ES L1 T. spiralis were used, the specific IgG were detectable from 40 dpi. In pigs infected with 1000 LI T. spiralis larvae, specific IgG was observed from 30 dpi when Ag ES L1 T. spiralis (W) and Ag ES L1 T. spiralis were used, but when Ag ES L1 T. spiralis (N) was used specific IgG were detectable from 40 dpi. In the group infected with the highest dose of T. spiralis larvae, specific IgG were detectable from 30 dpi when Ag ES L1 T. spiralis (N) and Ag ES L1 T. spiralis (W) were used, whereas when Ag ES L1 T. spiralis was used specific IgG were detectable from 20 dpi. The results strongly indicated that in the examined pigs, the specific IgG response against T. spiralis infection is dose dependent. Furthermore, it was shown that the high infectious dose induced earlier increasing of specific IgG response. Statistical analysis revealed a significant positive correlation between OD values obtained in procedures based on the three antigens. The results were statistically repeatable for procedures and for single pigs (P<0.01).