Global Food

Preventing Foodborne Illness Through Vaccination

By Fran Howard

Research being conducted by Dr. Fernando Leite, a veterinarian from Brazil and a second-year PhD student in Veterinary Medicine, could help veterinary scientists save human lives through better understanding the role the bacteria Lawsonia intracellularis plays in promoting foodborne illness caused by the deadly pathogen Salmonella.

Salmonella is the number-one bacterial foodborne pathogen in the world, and the leading cause of death due to foodborne illness,” says Leite. According to the Center for Disease Control, in Atlanta, Salmonella enterica is responsible for 1.5 million cases of foodborne illness in the United States each year. In Minnesota, 810 culture-confirmed cases of Salmonella infection in humans were documented in 2013 alone.

Pork products are often linked to foodborne illnesses caused by Salmonella. An earlier survey of pigs in Minnesota showed that most pigs and probably all swine herds in the state are carriers of Salmonella, but the bacteria rarely causes illness in swine. However, another bacterium, L. intracellularis, causes disease in pigs and has been implicated as contributor to increased shedding of Salmonella in the feces of pigs.

Leite and his advisor Richard Isaacson, PhD, a professor of microbiology at the College of Veterinary Medicine, hope to answer whether vaccinating pigs against L. intracellularis can help reduce shedding of S. enterica serovar Typhimurium, a common pathogen implicated in outbreaks of foodborne illness linked to pork products.

Leite’s project, Securing Food Supply and Improving Animal Health by Prevention of Swine Salmonella Infection, will test two hypotheses to better understand the role of L. intracellularis in allowing S. enterica serovar Typhimurium to colonize the pig’s intestinal tract. The research builds on previous work conducted at the College of Veterinary Medicine. Leite’s time on the grant is funded through a Global Food Ventures Fellowship award made possible through Minnesota’s Discovery Research and InnoVation Economy (MnDRIVE) funding.  

The first hypothesis Leite will test is whether a pig’s immune system by responding to an infection of L. intracellularis, becomes compromised to the degree that it is easier for Salmonella to move in and colonize the animal’s intestinal tract.

“Most bacterial infections cause inflammation,” says Isaacson. “Lawsonia does not. Does that suppression of the inflammatory response lead to opportunities for Salmonella to exist?”

To answer that question, Leite will conduct a controlled 11-week study to determine whether pigs infected with Salmonella that have not been vaccinated for L. intracellularis shed more Salmonella than pigs that are both vaccinated for Lawsonia and infected with Salmonella.  

“By the end of the project, I hope to determine whether using the Lawsonia vaccine will reduce the shedding of Salmonella in pigs,” he says. “If that’s the case, we can have a food safety impact while preventing disease caused by Lawsonia.”

In other words, vaccinating a herd against Lawsonia, could have a positive impact both on the pig by preventing disease and on those who eat pork products by reducing the opportunity for the potentially deadly Salmonella bacteria to enter the food chain.

The second hypothesis asks whether interactions among various bacteria, including S. enterica serovar Typhimurium and L. intracellularis, are responsible for increased shedding of Salmonella. In other words, do these interactions predispose an animal to more shedding of Salmonella?

“We will be sequencing the 16S RNA gene to determine all the bacterial species present in the gut of the pig to see what each bacteria (i.e., Salmonella and Lawsonia) does individually and in conjunction with other bacterial species to investigate why Salmonella is being favored,” says Leite.

Through this research, Isaacson and Leite hope to address a significant problem both within Minnesota and around the world, and they anticipate their findings will lead to intervention strategies—either vaccination against L. intracellularis or administration of probiotics—that swine producers can use to help protect herd health as well as the food supply.

“With reduced Salmonella carriage, swine producers could increase the productivity of their animals,” says Leite. “Less shedding of Salmonella could lead to more secure food production, preventing contamination and foodborne illness.” 

Leite received his DVM from the Federal University of Santa Maria, Brazil, in 2011. He then earned a master’s degree in Veterinary Microbiology and Immunobiology from Iowa State University while working at the National Animal Disease Center, part of USDA’s Agricultural Research Service. He plans to continue his career in research that focuses on developing novel strategies to improve animal health.

Global Food Ventures projects, which bring research, agriculture, and industry together to develop holistic approaches to ensuring a safe and sustainable food system, have benefited from more than $4 million in MnDRIVE funding in fiscal year 2016. During this period, Global Food Ventures has funded six new projects and awarded additional funding for nine of the 19 projected funded in fiscal year 2015. MnDRIVE funding also supports 7 Global Food Venture graduate students like Fernando.

MnDrive is an $18-million annual investment by the state of Minnesota. Global Food Ventures provides awards to researchers in the University of Minnesota’s College of Veterinary Medicine, School of Public Health, and College of Food, Agricultural and Natural Resource Sciences. Other MnDRIVE research areas include: Advancing Industry, Conserving Our Environment; Discoveries and Treatments for Brain Conditions; and Robotics, Sensors and Advanced Manufacturing.