Strategies to control PRRS: a summary of field and research experiences.

Various methods for the control of PRRS virus have been published. The technology of nursery depopulation (ND) appears to effectively control the spread of virus between members of endemically infected populations. ND consists of a strategic adjustment in pigflow based on the presence of specific serologic patterns as detected by the indirect fluorescent antibody test. This pattern indicates a low seroprevalence of antibodies detected in the breeding herd and recently weaned piglets (< or = 10%), in contrast to a high (> 50%) seroprevalence in 8 to 10 week old piglets. ND has been carried out on swine farms in the US and results indicate improvements in nursery piglet growth rate and mortality levels. Three examples are provided in the following text. Recently a modified live virus vaccine (RespPRRS, NOBL Laboratories/Boerhinger Ingleheim) has become commercially available. It is currently approved for use in piglets from 3 to 18 weeks of age; however, potential for the use in adult animals is currently under investigation.