Intensive research on salmonella in hog operations is beginning to unveil some clues about the disease.

Thomas Blaha, DVM, University of Minnesota, spearheads an ambitious salmonella research project involving 25 Minnesota hog farms. About 11,000 samples have been tested for salmonella in the multi-year project. The samples include 4,500 hog lymph nodes and 6,500 tests on the farm environment.

Results from the sampling show 10% of all the environmental samples (outside the barns, rodents, boots, etc.) were positive for salmonella. Surprisingly, only 5% of the hogs turned out to be salmonella positive.

"It is possible to have positive farms and negative pigs," Blaha states. "The producers apparently are doing something to keep those pigs from being salmonella positive."

He intends to look more closely at the theory that working procedures may be more important than the salmonella status of the hog farm.

Basically, the focus of the salmonella research is on all salmonella infection found on the farm, not just the kind that makes hogs sick. In fact, the vast number of salmonella infections found does not affect hogs, but has potential to affect humans.

Blaha and his fellow researchers are studying salmonella in hopes of learning how to reduce salmonella prevalence on the farm. This in turn will make pork safer in the food chain.

Salmonella Drops In Pork Pork producers need to be concerned about salmonella contamination today. USDA has stepped up their efforts to improve food safety. Salmonella, one of the most common food-borne pathogens, is a priority. USDA wants the entire food chain to reduce salmonella contamination.

USDA focused on meat and poultry processors first for improving food safety. Most packers must now operate a HACCP (Hazard Analysis and Critical Control Points) program. HACCP is designed to pinpoint where food contamination occurs and eliminate it.

Early government figures show HACCP programs are successful in reducing salmonella. Salmonella contamination of pork has dropped from 8.7% to 5.5% in 300 of the largest poultry and meat processing plants. Poultry also has dropped from 20% prevalence in broiler chickens to 10.4%. These drops in contamination rates occurred over a six-month period.

Farm Focus As the processors reduce their salmonella contamination rates, the focus will shift to the farm. Blaha hopes research will provide clues to develop good salmonella prevention plans.

Initial results from the research reveal some interesting findings. They are:

* Management procedures and practices have a significant impact on salmonella. Blaha suggests that daily working procedures and practices affect this. Maybe such things as animal movement, removal of spilled feed, and the cleaning and disinfecting of the environment including the hallways joining facilities plays a role in salmonella's spread. The movement of people and animals between areas also may have a great influence on salmonella.

* Dust is cited as a frequent source of salmonella. Blaha says dust makes a great medium for salmonella pathogens.

* Areas and farms appear to have their own salmonella patterns. The testing showed certain strains of salmonella were prevalent on certain farms. Even the strains between the environment and animals were somewhat different.

For example, Blaha says one strain of salmonella was isolated from just one farm. Most of the contamination was found in the environment and only some in animals on that farm.

On another farm, a different strain of salmonella was isolated. This strain, too, was prevalent in the environment, and less prevalent in the animals. Future Research

Blaha plans to continue the investigation into salmonella contamination. One focus of the research is on ways to quickly identify salmonella-infected areas on the farm. Hopefully, that will then lead to ways of cutting contamination of hogs, which in turn reduces the risk of contaminated slaughter facilities.