Estudio comparativo de la seguridad de distintas vacunas vivas atenuadas frente al síndrome reproductor y respiratorio porcino

Abstract

Porcine Reproductive and Respiratory Syndrome (PRRS) is one of the most significant diseases affecting swine production worldwide. The main clinical outcomes of the disease are reproductive failure in gestating sows and respiratory distress in growing pigs, especially in piglets. cThe causal agent, PRRS virus (PRRSV), is a small, enveloped, single-stranded positive-sense RNA virus of the Arteriviridae family.Although, in general, PRRS is clinically similar in North America and Europe, the respective strains differ in virulence and in antigenic and genetic properties. These differences have led to the classification of PRRSV isolates into two genotypes.The huge impact of PRRS in the swine industry has stimulated the development of various types of vaccines, including inactivated vaccines and modified-live virus (MLV) vaccines, for the control of the disease in both growing pigs and breeding females.MLV vaccines based on type 1 and type 2 viruses were originally developed for the control of PRRS in growing pigs, although some of them are now registered for the control of the reproductive form of PRRS.However, despite the extensive marketing of the various products developed by different laboratories, they have generated much controversy, mainly related to the safety of them. These suspicions derive both from the results carried out under experimental conditions as the evidences from the application of such vaccines in field working conditions. Thus, experimental studies carried out with Ingelvac® PRRS MLV, a vaccine based on a type 2 isolate, have demonstrated that vaccine virus replicates in vaccinated pigs, causes detectable viremia, persists in the organism of vaccinates for weeks and is shed by different routes causing the infection of sentinel pigs. In addition, the virus can cross the placental barrier in pregnant sows infecting the developing fetuses and can be transmitted to naive newborn piglets during lactation...