Submitted to: Research Workers in Animal Diseases Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 11/12/1996
Publication Date: N/A
Technical Abstract: An experimental study was conducted to evaluate a PCR-RFLP technique as a research tool to differentiate PRRSV isolates recovered from pigs infected with more than 1 virus isolate. A previously described PCR primer set which amplifies PRRSV ORF 5 was used for the RFLP strain differentiation. The study included 25 pigs at 3-4 weeks of age randomly divided into 5 treatment groups; Group 1= strict controls, Group 2= Modified Live PRRSV vaccine (MLV), Group 3= Wild type-PRRSV, Group 4= MLV/Wild type, Group 5= Wild type/MLV. Treatment groups 2-5 were all exposed to the indicated PRRSV strain on day 0 of the study. On day 7, treatment groups 4 and 5 were subsequently exposed to the second indicated strain of PRRSV to induce a dual infection. Pigs were periodically bled for 42 days post-infection. Sera were blindly submitted to 3 different laboratories. Each laboratory conducted virus isolation using either CL2621 cells, MARC cells or porcine alveolar macrophages. PRRSV isolates were then evaluated by PCR-RFLP to evaluate and compare the ability of the technique to identify dual infected pigs as well as differences between cell types. The differential test was able to accurately identify pigs infected with a single or both PRRSV isolates. In group 4 a dual virus infection was detected in 4 of 5 pigs between days 10-14 of the study. On days 14-28 wild type virus was the predominate virus isolated from these same pigs. Pigs in group 5, which were exposed to wild type virus on day 0 tended to have predominantly wild type recovered for the duration of the study, despite the secondary exposure to the MLV-PRRSV isolate. Some minor laboratory or cell line differences for sensitivity for virus isolation were noted.