Salmonella in food production

Salmonella is a genus of bacteria that live naturally in the environment, and scientists work hard to protect animals from the disease.

In an article by the American Society of Animal Science, Bradley Bearson, a microbiologist with the USDA Agricultural Research Service, said Salmonella can colonize a variety of animals, not just swine. In many cases, Salmonella infections do not cause symptoms.

“Often, Salmonella can colonize swine without causing obvious signs of disease,” said Bearson.

On rare occasions, pigs infected with Salmonella will have diarrhea, dehydration, septicemia and can even die. But even without obvious symptoms, there are two major reasons why scientists want to stop Salmonella infections in swine herds.

One reason is that even infections without noticeable symptoms, called “sub-clinical” infections, can hurt swine production. An infected animal may look normal, but fighting off an infection takes energy. Studies show that swine with subclinical infections do not gain body weight as quickly as uninfected swine. Lower body weight means less meat produced for human consumption.

Swine producers are particularly concerned with subclinical infections in newborn piglets. At the 7th International Congress on Farm Animal Endocrinology (ICFAE), in Bern, Switzerland in August 2011, researcher Jeff Carroll explained that piglets face extra immune challenges because they are also at risk for hypothermia. Piglets get cold easily, and sick piglets have to divide their energy between fighting infection and staying warm.

Carroll, a research leader for the USDA Agricultural Research Service Livestock Issues Research Unit, conducted an experiment where piglets were given injections of Lipopolysaccharides as an immune “challenge.”

“The pigs that were maintained in the warm environment exhibited no visual signs of illness.” Carroll said. But the cold pigs “redirected any nutrients they had toward survival.”

Carroll said it is important to study how temperature affects immune response. Carroll has also found that cattle face immune challenges when subjected to high temperatures.

It is important for animal scientists to study the cases when subclinical infections affect growth. With healthier animals, producers can raise more food to feed the world.

Bearson said good Salmonella control measures should include a biosecurity program. He said it is also important to understand gut health in animals and the role of feed additives and vaccines in controlling infection.

“A single management strategy will not be sufficient to consistently reduce pathogen colonization,” Bearson said.

A second reason to study animal diseases is the need to protect human health. Pathogens like Salmonella can have devastating effects on human health.

“Whenever pathogen exposure occurs due to Salmonella being present in food, water or the environment, there is a risk of spread to other animals as well as a potential risk of human disease,” Bearson said.

Animal producers work to prevent Salmonella in herds, and food producers take specific, government-mandated steps to keep meat, milk and eggs safe. But sometimes, contamination reaches the public. According to Centers for Disease Control statistics, Salmonella infections were the cause of 62 percent of hospitalizations due to food-borne illness in 2008. In 2008, 13 people in the United States died after contracting Salmonella.

Officials tell consumers to wash their hands and cook food thoroughly. Food safety experts agree, and many say it is important to take prevention a step further; to keep food production safe, scientists need to understand how diseases spread between animals and humans.

Learn more about how scientists are stopping Salmonella

Learn about the government regulations that protect your food