Comparison of techniques for controlling the spread of PRRSV in a large swine herd

Objective: To evaluate medicated offsite weaning (MOW),partial depopulation (PD), and the use of a modified live virus vaccine (MLV) as possible techniques to control porcine reproductive and respiratory syndrome virus (PRRSV). Methods: Four groups of 30 pigs from a PRRSV-infected farm were included in the study. Serum antibody responses to PRRSV (IFA), Mycoplasma hyopneumoniae (Tween-ELISA), and Actinobacillus pleuropneumoniae (BAHIA) were examined and bacteriology was performed at days 21, 35, 60, 90, 120, and 150 in all groups. We also measured average daily gain (ADG), mortality, and incidence of cough from 10 days of age to slaughter. PigMON® data were collected at slaughter. Results: MOW was the only technique able to maintain PRRSV-negative animals. PD and MLV resulted in a decrease in PRRSV seroprevalence. Even though PD was unable to eradicate PRRSV, performance was improved after this procedure was initiated. Differences in performance were not seen between the PD and MLV groups. Implications: Medicated offsite weaning may be able to stop the spread of PRRSV. Partial depopulation will reduce the decreased growth performance associated with PRRSV. Modified-live virus vaccine did not improve performance compared to partial depopulation in herds infected with PRRSV.