Porcine reproductive and respiratory syndrome (PRRS) is a viral disease of swine which causes serious economic losses in the majority of swine producing countries, including Poland. The agent of the disease is the PRRS virus (PRRSV) from the Arteriviridae family. PRRSV strains belong to two genotypes: European (PRRSV-EU) and American (PRRSV-US). They differ genetically and antigenically. Both genotypes are present in Europe, America and Asia, and their identification is important in order to control the disease by vaccination. ELISA tests are most frequently used for PRRS diagnosis. The aim of the study was to develop ELISA tests for general PRRS diagnosis and for discriminating seroconversion to PRRSV-EU from seroconversion to PRRSV-US. In order to do this an efficient method of nucleocapsid (N) protein expression in E. coli was developed and N proteins from PRRSV-EU and PRRSV-US strains were used as antigens. Mixed antigens of two strains were used in general purpose ELISA (PIWet PRRS ELISA) and split antigens were used in discriminatory ELISA (PIWet PRRS R ELISA). The studies showed that while the sensitivity of the PIWet PRRS ELISA is similar to that of reference HerdChek PRRS 2XR ELISA (IDEXX), its specificity seems to be higher. The newly developed test was less prone to false positive results than the IDEXX test. The discriminatory test, PIWet PRRS R ELISA, allowed precise identification of pigs infected with single genotype, PRRSV-EU or PRRSV-US. Additionally, based on serological examination of pigs from several age groups, it allowed the simultaneous circulation of two genotypes within a farm to be identified. The value of the developed tests was proven during routine diagnostic practice.
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