Submitted to: American Association of Swine Practitioners Proceedings
Publication Type: Proceedings
Publication Acceptance Date: March 1, 1997
Publication Date: N/A
Technical Abstract: Porcine reproductive and respiratory syndrome (PRRS) is a virus-induced disease of swine recognized by predominant clinical signs of reproductive failure and respiratory disease. It is responsible for major losses within the swine industry despite the use of a modified-live vaccine that became commercially available for use in young pigs 2 years ago. Even though this first vaccine and a second, new vaccine are now labeled for use in non-pregnant swine, producers still undergo PRRS epizootics within their herds despite the best control plans. Additional information is needed on how the PRRS virus (PRRSV) is able to infect swine, persist in swine, and cause disease despite the substantial use of vaccine. This proceedings reviews our current studies in sows previously exposed to either field PRRSV or modified-live PRRSV vaccines and later bred to a boar. The sows were exposed to a "cocktail" of field PRRSV isolates during late gestation, a time when porcine fetuses are highly susceptible to transplacental infection. Results demonstrated that one exposure to PRRSV before breeding would greatly reduce the reproductive failure caused by a PRRSV challenge during late gestation. This work suggests some cross protection can develop in sows following vaccination and that vaccination of nonpregnant sows may reduce losses within a herd. Although this sounds like good news for the producer, not all vaccinated sows were protected which resulted in a small number of pigs that were either born infected with PRRSV or became infected after birth. This reminds us that vaccines are not perfect and one of the most important aspects of disease control is preventing the disease from entering the farm by using proper quarantine facilities and strict all-in/all-out animal movement.