Summary

Elimination of PRRS virus from infected farm through management strategies

Over the last 20 years the research institutions as well as swine veterinary practitioners have identified many different methods to eliminate Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) from pig farms. These include, amongst others, total depopulation/repopulation, partial depopulation and herd closure. Total herd depopulation and repopulation is a very successful model, but it is costly and useful particularly in a farm afflicted with other devastating diseases (e.g. App, SD) that are not amenable to elimination by other methods. This strategy may be the only feasible alternative for farrow-to-finish herds where ongoing replication of PRRSV in the growing stage does not allow for the elimination of the virus using the other techniques. Partial depopulation may be sufficient to eliminate the virus from small farms particularly from growing pigs, assuming the shedding from the breeding population has completely stopped. Herd closure follows the principles followed for TGE eradication when all animals are being exposed to the virus and no replacement gilts are introduced until the virus has completely disappeared from the farm. For PRRSV, this requires a long time; a minimum period of 7 months is recommended, but variations may be needed depending on the status of the farm and pig flow. The success rate using this strategy is above 90% for farms with segregated production. Successful PRRSV elimination will depend on the development of the stable in terms of immunity and virus free population. An additional condition to be met for a successful elimination plan is the implementation of strict biosecurity measures in order to prevent the farm from reinfection.

Key words: pig farms, PRRSV, elimination