In 2011, an outbreak of E. coli O157:H7 in Oregon killed one person and sickened more than a dozen people. The outbreak was eventually traced back to organic strawberries grown at an Oregon farm, but how E. coli had managed to contaminate the strawberries remained a mystery for some time afterward.
Eventually, state health officials traced the outbreak to deer that had been rummaging through the fields and leaving behind droppings that contaminated some of the strawberries. And animal feces on the farm have been implicated or strongly suspected in a number of other outbreaks.
Perhaps most notably, in 1996, the organic juice company Odwalla recalled all of its bottled juices containing apple juice after the products sickened more than a dozen people with E. coli, found to be most likely originating from deer. Wild pigs were also suspected as the cause of the massive 2006 E. coli outbreak from spinach.
But what if organic farmers had a natural, unobtrusive way to help reduce the risk of contamination from animal feces on the farm? Enter the dung beetle.
Researchers at Washington State University have just embarked on a study looking into how effectively dung beetles can suppress harmful pathogens on farms by managing the contaminated feces of animals. The study is spread over 45 farms in Washington, Oregon and California and is being supported by a $500,000 grant from the U.S. Department of Agriculture’s National Institute of Food and Agriculture Organic Research Extension Initiative.
The idea came from WSU entomology doctoral student Matt Jones, who told Food Safety News he was working on a study involving organic blueberry fields in Maine. The main concern on the farm was making sure that whitetail deer didn’t contaminate any blueberries with feces, and so Jones started to wonder if any feces-eating insects could be strategically used to reduce that risk.
“Organic farmers have so few options for reducing their risk of E. coli,” Jones said. “They fund an awful lot of post-harvest work for food safety, but relatively less is being done right on the farm, trying to work with what eats poop and what eats E. coli.”
In an earlier study, Jones and WSU Entomology Professor Bill Snyder inoculated animal feces with E. coli and monitored how dung beetles reduced the presence of E. coli on the feces after feeding. While they couldn’t say exactly how much of a reduction was made, they said it was statistically significant.
So how do dung beetles kill E. coli? Beyond eating it and using it to lay eggs, they also bury some of it, and some of the insects may even carry antimicrobials in their exoskeletons, Jones said, citing a study by a South Korean entomologist who found a species of dung beetle with exterior bacteria-killing properties.
A lot of the potential bacteria-killing capabilities of dung beetles simply haven’t been studied yet, Snyder said. This new research aims to fill in some of that informational gap.
Snyder noted that there’s little evidence for the effectiveness of some of the more expensive strategies farmers have taken to reduce the risk of fecal contamination, including extensive fence systems and poison rodent traps.
Instead, Jones and Snyder hope their research may demonstrate to farmers ways to use the natural organisms in their environment to mitigate fecal contamination.
Dung beetles have already been deployed in agriculture for other reasons. Australia, for example, has no native dung beetles, but cattle producers imported them to help manage manure.
In the field, Jones will monitor insect activity at a variety of integrated livestock/produce farms to see how feces are managed by the farm’s insects over time. In the lab, he’ll measure the survival rates of E. coli O157:H7 bacteria on feces and in soils collected by those farms while in the presence of various species of dung beetles.
“From a research perspective, it’s sort of an untapped area,” Jones said. “No one has really looked at a form of natural suppression for these foodborne pathogens.”
The research process is still too early in development to draw any conclusions for potential management strategies involving dung beetles, but the project includes funding for educational field days for farmers to learn how they might use the insects naturally occurring on their land.
In total, the research project is scheduled to proceed over three years.
“All different types of growers want to make sure people don’t get sick,” Jones said. “We want to try out some new ideas — introduce a new conversation.”© Food Safety News