Epidemiology: Do Food-Animal Viruses Cause Cancer in Humans?

Susan Van Dusen

His research has taken him around the world, and over the last 30 years, Eric Johnson, M.D., Ph.D., M.P.H., has developed an international reputation for his work.

Johnson, an epidemiologist, is an expert in the cancer-causing roles of chemicals and food-animal viruses.

He was recruited to UAMS in January 2012, with the Translational Research Institute, the Fay W. Boozman College of Public Health and the Winthrop P. Rockefeller Cancer Institute all pitching in to provide the laboratory he needs to further his research.

Johnson is in the second year of a five-year study that is focused on whether food-animal viruses are to blame for high cancer rates among poultry workers. The $3.7 million study is funded by the National Institute for Occupational Safety and Health.

“We know that certain viruses are potent cancer-causing agents in animals,” said Johnson, who chairs the Department of Epidemiology in the College of Public Health. “It is very common for animals to get cancers from these viruses. They are natural infections that have been identified in cattle, chickens, sheep and pigs.”

Viruses may not be the first thing that comes to mind when considering the causes of cancer, but at least six human viruses contribute to 10-15 percent of cancers worldwide: Epstein–Barr virus (EBV), hepatitis B virus (HBV), hepatitis C virus (HCV), human papilloma virus (HPV), human T-cell lymphotropic virus (HTLV-1) and Kaposi’s associated sarcoma virus (KSHV).

While scientists don’t know if food-animal viruses cause cancer in humans, there are troubling signs, said Johnson, who has served as a scientist on several projects with the National Institutes of Health (NIH) and the World Health Organization (WHO), including as an epidemiologist with the WHO International Agency for Research on Cancer in Lyon, France.

“Humans are widely exposed to these animals and we now know that humans do get infected with some of these viruses,” he said.

His research has looked at humans with the highest exposure to these viruses – those responsible for killing chickens, cows, sheep and pigs.

Dr. Eric Johnson

Eric Johnson, Ph.D., is researching food-animal viruses.

“Over the last 30 years we have demonstrated quite clearly that workers in poultry slaughtering plants and cattle slaughtering plants and pig slaughtering plants are dying at a very high rate of cancer,” Johnson said. “Other investigators all over the world have also confirmed these findings. So the question is, is it due to these viruses or other causes?”

The cancers experienced by the workers being studied vary widely, and include lung, esophageal, pancreas, liver and brain cancers.

Johnson’s study of poultry workers will consider other potential causes, such as exposure to cancer-causing agents produced in meat smoking, curing and cooking at high temperature. Frying meat converts the fat to powerful carcinogens that are released in the fumes, he said.

Johnson’s new lab will play a key role, providing the methods needed to examine cancer tissue samples from poultry workers and cancer patients across the United States.

“At the end of this study, we hope to have definitive proof that viruses present in animals used for food either do or don’t cause cancer in humans,” he said.