| Acute porcine reproductive and respiratory syndrome outbreaks in immunized sow herds: from occurrence to stabilization under whole herd vaccination strategy |
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Sung Ho Moon, Sung J. Yoo, Sang Hyun Noh, Taeyong Kwon, Dong Uk Lee, Sang H. Je, Myung Hyee Kim, Sang Won Seo, Young S. Lyoo |
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College of Veterinary Medicine, Konkuk University |
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| Abstract |
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Outbreaks of porcine reproductive and respiratory syndrome virus (PRRSV) in vaccinated sow herds from occurrence to stabilization were monitored and analyzed in terms of serology and reproductive performance. Three different conventional pig farms experienced severe reproductive failures with the introduction of a type 1 PRRSV. These farms had adopted mass vaccination of sows using a type 2 PRRSV modified live vaccine (MLV). Therefore, to control the type 1 PRRSV, an alternative vaccination program utilizing both type 1 and type 2 MLV was undertaken. Following whole herd vaccinations with both types of MLV, successful stabilization of PRRS outbreaks was identified based on serological data (no viremia and downward trends in ELISA antibody titers in both sows and suckling piglets) and recovery of reproductive performance. Additionally, through comparison of the reproductive parameters between outbreak and non-outbreak periods, it was identified that PRRSV significantly affected the farrowing rate and the number of suckling piglets per litter at all three pig farms. Comparison of reproductive parameters between periods when the different vaccination strategies were applied revealed that the number of piglets born in total and born dead per litter were significantly increased after the introduction of the type 1 PRRS MLV. |
| Key Words:
disease outbreaks, herd immunity, heterologous effects of vaccine, porcine reproductive and respiratory syndrome virus, reproductive failures |
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