NESTED PCR FOR DETECTION AND TYPING OF PORCINE REPRODUCTIVE AND RESPIRATORY SYNDROME (PRRS) VIRUS IN PIGS

A nested polymerase chain reaction (PCR) was developed to detect porci ne reproductive and respiratory syndrome (PRRS) virus. A common primer set for European and North American type isolates of PRRS virus was d esigned for reverse transcription PCR, and a specific primer set for e ach of the 2 type isolates was designed for nested PCR. The PCR that u sed a specific primer set detected the corresponding type of the virus at a level equivalent to 1 TCID50/100 mu l, but not the other type of isolates. Therefore, the method clearly differentiated the 2 types of virus from each other. The detection of PRRS virus by the nested PCR was as sensitive as virus isolation in cultures of porcine alveolar ma crophages from infected pigs at the acute stages, and was more sensiti ve from pigs at the convalescent stages. The infecting virus type was determined by use of 2 specific primer sets even when virus isolation was negative in naturally infected pigs. It was concluded that the nes ted PCR is useful for diagnosis and typing of PRRS virus and studies o f persistent infection by the virus.