Evaluation of the level of white-tailed deer fecal colonization by E. coli O157:H7 and the ecological role of dung beetles with the pathogen in produce farms.

Wildlife as a source of microbial contamination is a concern among public health and food safety agencies. Deer feces have been determined to be a source of E. coli O157:H7. We plan to use the lowbush blueberry agroecosystem as a conceptual model system in which to test broadly applicable, food safety questions. We plan to determine the level of white-tailed deer fecal colonization by E. coli O157:H7 and to explore seasonal dynamics of E. coli O157:H7 contamination within feces. Additionally, it is important to understand dung beetles’ role as a potential natural control agent of the pathogen, alternatively as a pathogen vector between feces and fruit, or as a potential pathogen reservoir. Understanding the level of white-tailed deer fecal colonization by E. coli O157:H7 and subsequently, the ecological role of dung beetles in agriculture has strong implications for any system in which vegetables or fruits are at risk of wildlife fecal contaminants. We will determine the levels of pathogenic E. coli O157:H7 in deer fecal samples associated with the full geographic range of Maine’s lowbush blueberry. In addition we will conduct a laboratory study to elucidate dung beetle ecology as it relates to the suppression and/or transmission of pathogens.

Wildlife as a source of microbial contamination is a concern among public health and food safety agencies. Deer feces have, on multiple occasions, been determined as the source of E. coli O157:H7 contamination of produce. We plan to use the lowbush blueberry agroecosystem as a conceptual model system in which to test some broadly applicable, food safety questions. We will evaluate the level of white-tailed deer fecal colonization by E. coli O157:H7 and to explore seasonal dynamics of E. coli O157:H7 contamination within feces. Additionally, we feel it is important to understand dung beetles’ ecological role as a potential natural control agent of the pathogen, alternatively as a pathogen vector between feces and fruit, or as a potential pathogen reservoir. Understanding the level of white-tailed deer fecal colonization by E. coli O157:H7 and subsequently, the ecological role of dung beetles in agriculture has strong implications for any system in which vegetables or fruits are at risk of wildlife fecal contaminants. We plan to determine the levels of pathogenic E. coli O157:H7 in deer fecal samples associated with the full geographic range of Maine’s lowbush blueberry. In addition we plan to conduct a laboratory study to elucidate dung beetle ecology as it relates to the suppression and/or transmission of pathogens. We will use the full range of Maine’s lowbush blueberry crop and prevalent white-tailed deer feces as a conceptual model system in order to develop a sampling protocol for examining the levels of pathogens in wildlife feces within agricultural systems. We will determine the level of white-tailed deer fecal colonization by E. coli O157:H7 within the context of the lowbush blueberry system and seek to, eventually, extend these methods to other systems. We will develop a model relating potentially heightened seasonal prevalence of E. coli O157:H7 found in deer feces with harvest period of lowbush blueberry. We will test for contamination of any blueberry from sample sites of any feces samples testing positive to E. coli O157:H7 in order to explore the relationship between fecal contamination and fruit contamination. This will have powerful monitoring and management implications. Lastly, we will perform a lab study to determine ecologically important dung beetle/E. coli O157:H7/fruit relationships. The anticipated result of our proposed research on the produce industry is to provide information that will allow the quantification of risk due to E. coli O157:H7 contamination of deer feces in fruit and vegetable fields. In addition, we aim to determine seasonal dynamics of E. coli O157:H7 contamination within feces and provide proof of concept for novel ideas in understanding the ecological role of dung beetles in suppression and/or transmission of pathogens.

1. Use the full range of Maine’s lowbush blueberry crop and prevalent white-tailed deer feces as a conceptual model system in order to develop a sampling protocol for examining the levels of pathogens in wildlife feces within agricultural systems. 

2. Develop a model relating potentially heightened seasonal prevalence of E. coli O157:H7 found in deer feces with harvest period of lowbush blueberry. 

3. Test for contamination of any blueberry from sample sites of any feces samples testing positive to E. coli O157:H7 in order to explore the relationship between fecal contamination and fruit contamination 

4. Perform a lab study to determine ecologically important dung beetle/E. coli O157:H7/fruit relationships.

While finding lower levels of the pathogenic E. coli O157:H7 in the presence of dung beetles was a novel and interesting finding, regarding food safety, the fact that the beetles manipulated and fed on the scat without transmitting the pathogen to the fruit, is equally as important as the suppression of the pathogen in the soil. Resulting lower levels of pathogenic E. coli O157:H7 in the soil due to dung beetle activity would not be such a useful ecosystem service if beetles were acting as a vector of the pathogen from scat to the fruit. 

Major findings: 

• A wildlife feces survey was done to examine the levels of E. coli O157: H7 within lowbush blueberry crop systems and it confirmed that E. coli O157: H7 is present at low levels (6 of 300 individual samples) in the feces of wildlife found within Maine wild blueberry fields. 

• As five of the positive samples were collected in the late growing season of lowbush blueberry (early September), close to harvest-time we can say that, though the risk of infection in the wildlife population appears to be low, the risk for food contamination remains. 

• To test the potential for infected deer to directly transmit E. coli O157:H7 to lowbush blueberries, a field study was performed and it indicated that, when blueberries come in direct contact with contaminated deer feces, fruit contamination is possible and that can persist for greater than 72hours. 

• Studied were done to understand the role of dung beetles in the potential suppression/transmission of E. coli O157:H7 and our results showed that the dung beetles did not play a role in vectoring pathogenic E. coli O157:H7 to the lowbush blueberry fruit and they did not show any feeding preference between pathogeninoculated feces and non-pathogen inoculated feces. 

• Dung beetles when they feed on scat, E. coli O157:H7 can be moved into the soil. But, the lower levels of pathogenic E. coli O157:H7 recovered from microcosms containing beetles (as opposed to those without beetles) indicates that some aspects of dung beetle biology are contributing to this decrease.