A new poultry vaccine that reduces the occurrence of salmonella in eggs has been developed by an Iowa State researcher.

Veterinary microbiologist Theodore Kramer said the new vaccine could improve food safety.

Kramer adapted salmonella to a phagocyte, a cell that can engulf and digest bacteria and other small particles, and administered the adapted salmonella to hens via their drinking water.

Once the hens received the vaccine and were subsequently infected, Kramer discovered that the hens had not transmitted the bacteria to their eggs.

“The adapted salmonella no longer caused disease but produced a strong immunity,” Kramer said.

Kramer also said the vaccine helps to reduce the spread of salmonella to other chickens through contaminated feces.

The vaccine targets bacteria called salmonella enteritidis, which cause food poisoning in humans. The bacteria, which cause salmonellosis are found in the intestinal tracts of animals and humans.

The bacteria are difficult to detect in chickens. Infected hens usually do not appear sick, and chicken producers often find the current tests time-consuming and costly, Kramer said.

“In a unit of 10,000 hens, it would be difficult to test every bird,” Kramer said. “If salmonellosis is found, about all the producer can do is destroy all of the hens. That can be financially ruinous to the producer.”

Kramer said chicken eggs account for about half of all the thousands of U.S. human salmonellosis cases yearly.

“Salmonella costs the United States $2.5 billion a year,” Kramer said.

Janet Anderson, executive director for the Iowa Egg Council in Ames, said Iowa is among the nation’s top five egg-producing states. Five-and-a-half billion eggs are produced annually in Iowa, Anderson said, and the Iowa egg industry is growing rapidly.

Eating ice cream, mayonnaise or salad dressing made with contaminated raw eggs is the most common way humans contract salmonellosis from eggs.

A person suffering from salmonellosis poisoning may have abdominal cramps, nausea, vomiting and diarrhea.

“The effects of salmonellosis can be far-ranging, ” Kramer said. “A contaminated food product produced in a large quantity and distributed widely can cause illness in several states.”

The vaccine still requires additional testing and approval from the U.S. Department of Agriculture before it can be used by egg producers.

“The vaccine must past tests for safety, efficiency and reproducibility before it can be approved,” Kramer said.