#04-201

Complete

Date Full Report Received

03/21/2006

Date Abstract Report Received

07/25/2007

Investigation

Institution:
Primary Investigator:
Co-Investigators: Annette O’Connor

Since 1995, the Danish swine industry has conducted an on-farm Salmonella control program to categorize production sites as to their risks for Salmonella contamination. This classification has been used to schedule transport and to harvest herds of similar statuses to reduce antemortem Salmonella cross contamination. Danish herd classifications for Levels I, II, and III have remained relatively static at approximately 95%, 3.3%, and 1.6%, respectively (Nielsen et al., 2001). In 2002 similar values (91%, 8%, and 1%) were obtained from a large Midwestern USA sample. In 2004 a similar sampling scheme compared 502 herds from 2002 and 2004 and found classifications for Levels I, II, and III to be 79%, 14, and 6%, respectively. This increase was also reflected in an approximately 2X increase in total samples testing positive for Salmonella antibodies. Analysis of these data suggests that the prevalence of Salmonella within production units was not temporally stable and that the prevalence of Salmonella exposure in Midwestern swine differed between these surveys for small volume but not large producers. The results highlight that classifications assigned to producers in 2002 were not likely to be the same in 2004. These findings have implications for Salmonella control schemes that use on-farm classification schemes to impose marketing restriction on herds based upon antibody prevalence levels.