AHRI report No.36

Safety and Efficacy Evaluations of the Attenuated Porcine Reproductive andRespiratory Syndrome Viruses

Animal Health Research Institute, Council of Agriculture, Executive Yuan

Twenty-two piglet without anti&dy titer against pcthne reprcdwtive and respiratory syndrome (PRRS) virus were inoculated with two attenuated PRRS viruses, PRRSV-YS-MARC 52 and PRRS V-WS-MARC 62, to evaluate the safety and efficacy. On the 21 th days pt vaccination, 10 pigs vaccinated with one and one-tenth doses Of PRRSV-YS-MARC 52 and PRRSV-WS-MARC 62 were challenged with the field isolat PRRSV-TD-PAM2. All of the challenged pigs were sacrificed and examined for grcGs lesions on the 26th days pt challenge. Result demonstrated that bth the PRRS V-YS-MARC 52 and the PRRSV-WS-MARC 62 were safe for pigs either they received one or one-tenth dose of ‘iruses. For contact infection, all of the 4 pigs, which were renned with the infected pigs, sexcconvered to positive on the 5th weeks poet infection. These result undicael that piglet received either the PRRSVYS-MARC 52 or the PRRS V-WS-MARC 62 virus excreted ‘Anuses and infected new host. Inaddition, twopregnantsows received lOdoses ofPRRSV-WS-MARC62at the 87th-93th days of gestution and they delivered 18 healthy piglet lat. The colcetrum from bc’th sows contained titers (>2,SEOX)of indirect fluorescent anti&dies. Our studies suggest that the PRRS attenuated viruses are safe for all age of pigs.

Porcine regcductive and respiratory syndrome 'inus, Attenual vaccine