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United States Department of Agriculture

Agricultural Research Service

Title: Evidence for Local Spread of Porcine Reproductive and Respiratory Syndrome Virus

Authors
item LAGER, KELLY
item Mengeling, William
item Wesley, Ronald

Submitted to: Swine Health and Production
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 16, 2001
Publication Date: N/A

Interpretive Summary: Porcine reproductive and respiratory syndrome (PRRS) is a disease of swine caused by the PRRS virus (PRRSV). Currently it is the most serious disease faced by the US swine industry causing reproductive losses in the sow herd and respiratory disease in young pigs. Field reports have suggested that transmission of PRRSV between farms can occur by direct contact (pig-to-pig and use of virus-contaminated semen) and by indirect contact (blowing through the air; sharing of PRRSV-contaminated equipment, tools, or vehicles; and the possibility that insects, birds, or mammals could carry this virus). Experimental studies have confirmed the role of direct transmission in the spread of PRRSV from infected to noninfected swine by way of pig contact and use of virus-contaminated semen while results from indirect transmission studies have not been so straightforward. In this report we describe evidence from a field investigation suggesting area spread of PRRSV occurred among swine farms in nort-central Iowa without any direct contact by swine. PRRSV was detected in swine from seven different farms located relatively close to each other that all had clinical disease within about 2 weeks of each other. Genetic tests indicated the virus from each farm was very closely related if not the same virus. There was no apparent link between any of these farms that would account for how the same virus could have been transmitted among them. Some of the farms were a few miles apart and one farm was about 22 miles from the others suggesting it is more likely that a common virus was transmitted among these farms through the air as either free virus or it was associated with an insect or bird.

Technical Abstract: Porcine reproductive and respiratory syndrome (PRRS) is a disease of swine caused by the PRRS virus (PRRSV). Currently it is the most serious disease faced by the US swine industry causing reproductive losses in the sow herd and respiratory disease in young pigs. Field reports have suggested that transmission of PRRSV between farms can occur by direct contact (pig-to-pig and use of virus-contaminated semen) and by indirect contact (blowing through the air; sharing of PRRSV-contaminated equipment, tools, or vehicles; and the possibility that insects, birds, or mammals could carry this virus). Experimental studies have confirmed the role of direct transmission in the spread of PRRSV from infected to noninfected swine by way of pig contact and use of virus-contaminated semen while results from indirect transmission studies have not been so straightforward. In this report we describe evidence from a field investigation suggesting area spread of PRRSV occurred among swine farms in nort-central Iowa without any direct contact by swine. PRRSV was detected in swine from seven different farms located relatively close to each other that all had clinical disease within about 2 weeks of each other. Genetic tests indicated the virus from each farm was very closely related if not the same virus. There was no apparent link between any of these farms that would account for how the same virus could have been transmitted among them. Some of the farms were a few miles apart and one farm was about 22 miles from the others suggesting it is more likely that a common virus was transmitted among these farms through the air as either free virus or it was associated with an insect or bird.

Last Modified: 7/28/2014
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