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Porcine Reproductive and Respiratory Syndrome (view source)

Revision as of 17:24, 27 August 2010

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==Transmission and Epidemiology==

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Following infection of a naive herd, exposure of all members of the breeding population is inconsistent, leading to the development of naive, exposed, and persistently infected subpopulations of sows. This situation is exacerbated over time through the addition of improperly acclimated replacement gilts and leads to shedding of the virus from carrier animals to those that have not been previously exposed.

The primary vector for transmission of the virus is the infected pig. Contact transmission has been demonstrated experimentally, and the spread of virus from infected seedstock originating from a single source has been described. Introduction of infected seedstock can lead to the introduction and coexistence of genetically diverse isolates of PRRS virus on the same farm. Controlled studies have indicated that infected swine may be longterm carriers, with adults able to shed PRRS virus for up to 86 days after infection, while weaned pigs may harbor virus for 157 days. Experimentally infected boars can shed virus in the semen up to 93 days after infection.

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