Submitted to: American Association of Veterinary Laboratory Diagnosticians
Publication Type: Proceedings
Publication Acceptance Date: October 7, 1999
Publication Date: N/A
Technical Abstract: Porcine reproductive and respiratory syndrome (PRRS) is a disease of swine caused by the PRRS virus (PRRSV). PRRS was first recognized in 1987 and since then it has become the number one infectious disease problem for the swine industry. It causes acute reproductive failure in sows (abortions, stillborn and weak-born pigs) and respiratory disease in young pigs. Based don field reports, transmission of PRRSV is thought to occur by direct contact between pigs, use of infected semen, and aerosol transmission that results in virus spread among pigs on the same farm as well as between farms. Experimental studies have conclusively demonstrated direct contact and infected semen can consistently transmit virus; however, studies on aerosol transmission have been equivocal with inconsistent transmission occurring over short distances. This report describes a field investigation of a cluster of PRRS cases that all experienced clinical signs within a few days of each other. PRRSV was isolated from 7 farms an based on genetic analysis, each isolate was similar if not the same virus. No common denominator or relationship was detected among the cases that would account for the presence of a similar if not identical PRRSV isolate on each of the farms indicating this cluster of PRRS epizootics represents area spread of PRRSV without any direct transmission by swine, humans, or fomites. The possibility of a biologic or mechanical vector (birds, insects) can not be ruled out; however, the role of small animals in this area spread of PRRSV seems remote because distances between farms involved several miles and one farm was about 20 miles from the next closest case.