The U.S. Centers for Disease Control and Prevention (CDC) believes that about 17% of Americans get sick from foodborne diseases each year. The CDC estimates that 59% of these illnesses are caused by viruses and 39% are caused by bacteria. The some of the most commons pathogens are Norovirus, Salmonella, Clostridium perfringens, Campylobacter and Escherichia coli.

• Norovirus is a very contagious virus that can be passed between people, or via contaminated food, water, surfaces, including a fruit or vegetable’s surface. Norovirus often causes symptoms (vomiting, diarrhea) and outbreaks in areas where many people are confined for a period of time (cruise ship, camp) or at restaurants where people are touching food. The best way to prevent Norovirus spread is through hand washing and safe food handling practices.
• Salmonella are bacteria that live in the intestines of humans and animals and cause abdominal cramps and diarrhea. These bacteria can contaminate soil, water and food: often beef, poultry, milk, fish, eggs, but also fruit, vegetables and processed food. As Salmonella is transmitted by small amounts of animal feces, it can also be transmitted when humans touch infected animals. Hand washing, proper cooking and safe food handling help prevent Salmonella infection.
• C. perfringens are bacteria that are found in the environment, as well as in human and animal intestines (including their waste). This bacterium can live and grow rapidly on food that is not heated above 140°F. Food that is being saved to serve later is especially susceptible. Once infected, symptoms in humans include abdominal cramps and diarrhea.
• Campylobacter is a bacterium that is prevalent in animals, such as cattle and poultry, and can be passed into our food chain via contaminated water or animal products. These bacteria cause diarrhea, abdominal pain and fever, and is best prevented by washing hands, washing produce, and eating pasteurized and well-cooked animal-source foods.
• E. coli are bacteria found in the environment, foods, and intestines of people and animals. Not all strains of E.coli are harmful to humans, but those that produce a Shiga toxin are. These strains can be passed via human or animal feces, including via consumption of unpasteurized or undercooked food, contaminated water droplets or dirty hands.

While these foodborne diseases are often linked to undercooked foods, poor handwashing practices or inadequate food handling practices, two researchers at Cornell University’s College of Veterinary Medicine in the Department of Population Medicine and Diagnostic Sciences are working to better understand the transmission pathways of these pathogens so that food producers can ensure that the food we consume is safe.

Dr. Renata Ivanek, associate professor of epidemiology, specializes in the epidemiology and public health impact of infectious and foodborne disease. One approach that Ivanek uses is ‘landscape epidemiology,’ which helps define how variables like land cover, soil type, or aquatic features affect the transmission of pathogens.

Using these methods, Ivanek has described how Salmonella, E.coli, and other foodborne pathogens are spread through produce (fruit and vegetables). Ivanek explains, “Our eating habits are changing—we all like to eat fresh fruits and vegetables, and that’s great. But it can increase risk.” A key problem stems from the fact that most produce growers rely on surface water from nearby lakes or streams to irrigate their crops. “This water may have pathogens in it, picked up from animal and human waste upstream,” says Ivanek. The contaminated water can splash up onto the leaves and fruit of crops. Unless well cleaned and well processed, these pathogens can be passed along to the consumer. Having developed epidemiological models to show pathogen spread, Ivanek is now studying different methods, such as UV light treatments, to treat irrigation water before it is distributed to crops.

Ivanek also applies statistical and mathematical modeling to the issue of foodborne pathogens in cattle and swine production. “I’m trying to pinpoint the natural drivers of variability so we can find intervention strategies,” Ivanek explains. To date, these models have shown how pivotal variables like rainfall and ambient temperature can be in disease transmission. Ivanek is now testing the modeled findings in the field to validate possible solutions.

Dr. Craig Altier, professor and chair of the Department of Population Medicine and Diagnostic Sciences, is leading a different approach to improve the safety of the food we eat. Building on prior research, including preventing or reducing Salmonella virulence in tomatoes, Altier is now investigating ways to disable harmful Salmonella bacteria in livestock animals so that it does not cause infection. Altier has found that certain substances similar to fatty acids produced in the intestine can neutralize the process by which virulent Salmonella attacks cells in the gut. Without the ability to attack their host, the Salmonella bacteria “lose their competitive advantage in the bacterial population,” Altier explains. “The other bacteria will eat the available nutrients.” So far, the approach is being tested in mice, and Altier’s team will begin testing it in chickens shortly.

This story was written by Gen Meredith and adapted from a profile first published in ‘Scopes Spring 2016 issue on Food and Public Health.