Monitoring the prevalence of Lawsonia intracellularis antibodies using serial sampling i growing and breeding herds

摘要

The objective of this study was to determine the prevalence of Lawsonia intracellularis serum antibodies and the time of seroconversion in growing and breeding herds using the immunoperoxidase monolayer assay. Growing pigs were tagged and bled at weaning (approximately 3 weeks of age) and subsequently bled every three (3) weeks until reaching market weight. Breeding animals were tagged and bled at entry into the breeding herd and subsequently bled every three (3) weeks for eight (8) blood collections(24 weeks total) until all bleedings had been completed. All serum samples were analyzed for the presence of L. intracellularis antibodies using the immunoperoxidase mono-layer assay (IPMA). Fifteen of twenty (75%) growing herds had evidence of L. intracellularis antibodies. Seroprevalence was highest in growing herds near marketing age (Figure 1). Within-herd seropreva-lence in positive growing herds ranged from eleven to ninety-two percent (Table 1). Seven of nine (78%) breeding herds had evidence ofL. intracellularis antibodies. Seroprevalence in breeding herds had two peaks, first near the time of herd entry and secondly late in the study (Figure 2). Within-herd Seroprevalence in positive breeding herds ranged from five up to sixty-one percent (Table 2). L. intracellularis serum antibodies were common in both growing and breeding herds. Serial blood sampling was shown to be important when conducting herd serological investigations for L. intracellularis due to the relatively short time period that pigs are seropositive.