Swine Vet Center, P.A. – “Using Direct Virus Exposure in Conjunction with Modified Herd Closure for a PRRS Eradication”

Summary:
Direct virus exposure has been used in many herds because it accelerates a herd’s return to more normal performance and generates negative pigs to flow downstream into its production system. There are many procedures that have been used for PRRS eradication. Herd closure with offsite breeding projects is one of the procedures that has sometimes been successful. The challenge has been to correctly identify when the last pigs have been exposed to virus. Data from previous work done with herd closures suggest that the herd needs to be closed for at least 200 days from the date of last infection/exposure before allowing PRRS-negative animals back into the population. However, knowing when the last animals were truly infected/exposed in the herd is never a certainty. Direct virus exposure to the herd infects/exposes all the animals at a given point in time, therefore eliminating the question of when the last animal in the herd was exposed. This project will determine if the practice of direct virus exposure coupled with herd closure can be used to eradicate PRRS from a herd.

Objective:
This project has two objectives. First, to determine if PRRSV-negative pigs can be generated from PRRSV-positive herds and second, to determine if PRRSV can be cost-effectively eradicated from a herd using the combination of virus exposure and herd closure.

Relevance:
Currently, there are no scientifically valid studies that document the success of direct virus exposure procedures in herds; only anecdotal information is available. This leaves producers with little good information on how to successfully utilize these procedures. Direct virus exposure has the potential to accomplish complete herd exposure and firmly establish the time of last herd infection. Knowing this information would allow for a consistent method of evaluating the outcomes of herds choosing to use direct virus exposure.