Effect of fetal PRRSV infection on the development of the porcine immune system

摘要

Over die last decade a phenomenal amount of resources lias been applied towards the control and prevention of porcine reproductive and respiratory syndrome vi'RRS), and in some respects, the swine industry is not much better oil than when PRRS was still known as Mystery Swine Disease. One major challenge for the veterinary community is to fully understand PRRSV transmission since this is one of the keys to controlling and preventing the disease, a task of utmost importance for pork producers. Each year in the United States there are many acute cases of PRRS reported in naive herds demonstrating the transmission of PRRS virus (PRRSV) still occurs despite the implementation of many biosecurity controls. Most of these cases are attributed xo direct virus transmission among swine (pig-to pig contact or the use or virus-contaminated semen) occurring on (arms that practice lax biosecurity. However, there are numerous PRRS epidemics occurring on farms with strict biosecurity practices. In these cases it is assumed that either indirect transmission (aerosol, tomites, biologic or mechanical vectors as routes of transmission) occurred or there were actually PRRSV-infected pigs or semen introduced in'n the herd from what were thought to be PRRSV-free sources. The objective of the study reported here is to investigate the latter possibility, i.e., what are the chances of a PRRS-positive pig slipping into a herd.