U.S. Department of Agriculture (USDA) and Iowa State University both report declining salmonella infection levels.

USDA Food Safety and Inspection Service's (FSIS) recent release of salmonella performance standards for meat and poultry products shows reduced contamination levels.

FSIS collects and analyzes data to verify compliance with the Hazard Analysis and Critical Control Point (HACCP) program.

The launch of HACCP in 1996 helped improve sanitation at slaughter, says James D. McKean, Extension swine veterinarian at Iowa State University.

FSIS sampling covers broilers, market hogs, cows/bulls, steers/heifers and ground beef, chicken and turkey.

The baseline prevalence for salmonella contamination is 8.7% for market hog carcasses. Random positive test results are: 3.8% in 2003; 4.29% in 2002; 5.03% in 2001; 5.3% in 2000; 7.26% in 1999; and 10.65% in 1998.

Iowa State Study

McKean classified Midwestern hog farms for salmonella prevalence by testing meat juice samples at seven Iowa packing plants.

There were 1,131 producers who qualified for sampling, marketing at least one lot of hogs per month (20-180 head).

Distribution of salmonella prevalence mirrored that of Danish herds where a test-and-control program has been in place since 1995.

Ignoring herd size, 90.2% of Iowa herds surveyed were negative or in level 1 (less than 25% prevalence); 8.2% were in level 2 (25-50% prevalence); and 1.6% fell into level 3 (over 50% prevalence). The prevalence levels were designed after the Danish program.

The Danish program also tests carcass meat juice antibody levels for prevalence of salmonella, explains McKean. Some 95% of Danish herds are in level 1; 3.3% are in level 2; and 1.6% are in level 3.

“In the Iowa survey, at least one positive animal was submitted from 506 out of 1,131 producers (44.7%), demonstrating that exposure to salmonella during production is a common occurrence on a wide range of farms.

“These on-farm prevalence estimates do not demonstrate a link between significance for these exposures and salmonella contamination of pork, but do provide a useful benchmark for future studies,” says McKean.

The survey also indicates that size does matter. Larger producers had more variation in salmonella prevalence and more positive antibody results for salmonella, he says.

McKean plans to repeat the 2002 packing plant survey later this year, using the same herds.

In doing so, he hopes to derive some common themes that keep some farms consistently free of salmonella while others are consistently infected.

He admits the task is somewhat daunting. “It raises the issue that we may not know what the appropriate interventions are, and the Danes may not know what they are — because if they did, they would go into those level 3 herds and make them disappear.”

McKean spoke at the pork checkoff-funded Pork Quality and Safety Summit in West Des Moines, IA, in mid-August.