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Salmonella ELISA Serology from Weaned Pigs as an Indicator of Salmonella Circulation in Breed to Wean Sites

T. Fangman, D. Baumert, T. Painter, B. Whitt, M. Ptaschinski, G. ClineJune 7, 2016

INTRODUCTION

Understanding prevalence of Salmonella in market pigs has become a priority within USDA. With this priority pork production systems have a greater interest in understanding Salmonella prevalence in market pigs and the relationship of this prevalence to breed-to-wean sites. In a European study, a 90% reduction in breeding herd Salmonella prevalence reduced market pig Salmonella prevalence in the lymphnode by 66%.1

The objective of this study was to

  • Evaluate the ability of an indirect Salmonella ELISA antibody test (Vetsign™, Svanova) to detect Salmonella positive weaned pigs (5 weeks of age)
  • Determine if Salmonella antibodies at 5 and 9 weeks of age could be a predictor of Salmonella circulation at breed-to-wean sites.

MATERIALS AND METHODS

  • At risk breed-to-wean sites (R: 300-800 sows) within a large pork production system 
    1. Salmonella risk factors identified at the selected sites included:
    2. Open gutter flush
    3. Rodent feces observed in barn
  • Sanitation practices below expectations
  • Twenty, 5-week-old pigs from 12 breed-to-wean sites were tagged and bled post-nursery placement
  • If ≥ 6 (30%) of the pigs demonstrated Salmonella ELISA antibodies the prevalence was considered high
  • Pigs were retested 4 weeks later
  • Decreasing Salmonella ELISA antibodies from these paired samples could then be interpreted as decreasing maternal antibodies
  • If ≤ 5 weaned pigs were ELISA positive to Salmonella then the Salmonella prevalence of the breed-to-wean site was considered to be low

RESULTS

  • Sites A,B,C,E and F had ≥ 30% Salmonella ELISA positive pigs and that these ELISA titers decreased 4 weeks later in serial bled pigs (suggesting these antibodies were maternally derived)
  • ELISA titer rose at site D four weeks later in serial bled pigs (suggesting active exposure)
  • At sites G-L the Salmonella ELISA positive pigs were < 30%. Pigs at sites G-L were not retested

Table 1: % Positice Salmonella ELISA (20 pigs / site)

CONCLUSION

  • Salmonella ELISA titers in 5 and 9-week-old pigs appears to be a predictor of Salmonella circulation of breed-to-wean sites
  • Salmonella serological assays demonstrate the variation of maternal antibodies between the sites. Sites where high maternal antibody circulation has been identified are a concern and suggestive of increased Salmonella pressure at the breed-to-wean site
  • Further investigation is planned at the source sites from which the 5-week-old pigs demonstrating ≥ 30% positive findings originate

REFERENCES

  1. European Food Safety Authority Panel. EFSA Journl. 2010; http://www.efsa.europa.eu/en/efsajournal/pub/1547.htm.
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BIVI/STC/151008b