- 10 minutes
- Expertise article
- Shusei Toda, Sayoko Ishizeki, Yugo Watanabe, Yuko Kazuno, Hiromichi Ishikawa
Shusei Toda, Sayoko Ishizeki, Yugo Watanabe, Yuko Kazuno, Hiromichi Ishikawa
Summit Veterinary Services, Ltd. E-mail: toda@svs-jp.com
Introduction
Porcine respiratory and reproductive syndrome (PRRS) is a viral disease caused by PRRS virus (PRRSV). Major clinical manifestations are reproductive failure in breeding herd and respiratory disease in growing pigs. In PRRS endemic farms, comprehensive approach such as immunization of breeding and/or growing herd, enhanced biosecurity measures, prevention of viral circulation by controlled pig flow management is crucial to minimize the economic impact of PRRS (1). In 2018, increase of mortality in nursery was observed in a farrow-to-nursery farm in Japan and PRRS was suspected to be involved. This report documents the improvement of mortality in nursery by implementing series of PRRS control measures including PRRS monitoring utilizing oral fluid test, piglet immunization with modified live virus (MLV) vaccine, change of antibiotic treatment regimen and pig flow management.
Materials and Methods
1,100 sows were reared in a farrow-to-nursery farm in pigdense area in Japan. Piglets were moved from farrowing house to nursery at 25 days of age and from nursery to fattening house in a different site at 70 days of age. All-in all-out system was employed in farrowing house and nursery. In November 2018, increase of dead piglets suffering from respiratory disease was observed in nursery. In April and May 2019, wild type (WT) PRRSV gene was detected from serum and lung of piglets with 30-70 days of age. Monthly PRRS monitoring program by oral fluid test including PCR and sequence analysis of ORF5 gene started from June 2019. Oral fluid was collected by a rope method. Monitoring results showed the high frequency of WT PRRSV detection in isolation house where pigs with inadequate growth were gathered and reared. In addition, nursery adjacent to above isolation house showed similar monitoring result.
From June 2019, PRRS MLV combination vaccine (Ingelvac® 3FLEX, Boehringer Ingelheim Animal Health Japan Co., Ltd., 2 mL single intramuscular injection) was administered to piglets at weaning. In addition, tylvalosin premix was added to feed in nursery and pig flow was changed to abolish the isolation house. Monthly mortality in nursery was monitored to evaluate the impact of PRRS control measures.
Results and discussion
Decrease of mortality was observed immediately from June 2019, which indicated the positive impact of PRRS MLV vaccination to piglets and introduction of tylvalosin premix (Figure 1). Results of oral fluid test demonstrated the decrease of WT PRRSV detection (Table 1) and delayed PRRSV infection timing in nursery (Table 2), suggesting the additional positive impact of new pig flow management implemented from August 2019.
Conclusions
This report has demonstrated the positive impact of implementing appropriate PRRS control measures in a PRRS endemic farm. PRRS MLV vaccination to piglets contributed to reducing the viral load. Clinical symptoms were reduced by the diminished PRRSV replication with tylvalosin premix (2) and pig flow management was efficacious on preventing virus circulation. Furthermore, elucidating infection dynamics i.e. frequency of WT PRRSV detection and timing of infection by houses, by continuous PRRS monitoring utilizing oral fluid test is crucial to establish PRRS control strategy.
Figure 1: Monthly mortality rate in nursery
Acknowledgments
Boehringer Ingelheim Animal Health Japan Co., Ltd (Tokyo, Japan)
References
- Zimmerman J et al. 2019. Disease of Swine 11th Edition: 685-708 2. Stuart AD et al. 2008. The Pig Journal 61:42-28