Contamination of leafy green crops with foodborne pathogens: Are wildlife a problem?

Contamination of leafy green crops with foodborne pathogens: Are wildlife a problem?

Jan. 1, 2015 - Dec. 31, 2015

$197,429.00

Alan Franklin, Ph.D.
USDA-APHIS-WS

Sarah N. Bevins, Ph.D.

Final Report

Foodborne diseases cause millions of illnesses in the United States each year and some of these cases result in severe sickness and death. We propose to study whether or not wildlife contributes to foodborne disease risk by contaminating leafy green produce, such as spinach and lettuce, when they visit agricultural fields. There have been several instances where foodborne disease outbreaks are thought to have been related to wildlife presence in crop fields, but these links are poorly understood. By collecting data on when wildlife enter agricultural production areas, what species enter, where they enter, and how many of them are present at a given point in time, we can better understand if and where introduction of pathogens causing foodborne diseases might occur. We will also collect fecal samples from wildlife visiting produce fields and test them for three of the top microbial pathogens causing foodborne disease. This information will provide needed insight into the magnitude of the problem and will determine if actions should be taken to limit this risk and what those actions should be. Overall, our results will help balance the coexistence of wildlife habitat with protection of agricultural producers and human health from food-borne pathogens.

Technical Abstract

Microbial pathogen contamination of plant-derived foods can occur through multiple pathways, one of which is the introduction of pathogens into agricultural growing areas by wildlife. This is especially true for leafy green crops because, in some cases, they can incorporate pathogens into their tissues and because they are often eaten raw by consumers. Despite this risk, there are currently limited robust data on patterns of wildlife activity in agricultural areas.  We propose to look at wildlife incursion into leafy green crops by using camera traps to elucidate where these events occur, what the frequency of visits are, and how many individuals are seen during incursion events. These analyses will incorporate the landscape characteristics associated with incursion events (i.e. distance to natural habitat blocks) and the location of incursions within leafy green fields (i.e. edge effects within the fields). In addition, fecal samples and nearby leafy green cuttings will be collected and screened for Shiga toxin-producing Escherichia coli, Salmonella enterica, and noroviruses. Positive samples will be further characterized through serogrouping, serotyping, and genotyping strategies. We plan to conduct this research in the San Luis Valley of Colorado in cooperation with researchers at the University of Wyoming and Southern Colorado Farms, LLC. Data collection will be performed by researchers at the USDA-APHIS National Wildlife Research Center, diagnostic analyses on fecal and lettuce samples will be performed at the University of Wyoming, and statistical analysis of both pathogen and camera data will be carried out at the National Wildlife Research Center. The anticipated outcome is that combining baseline wildlife incursion data with basic pathogen screening will provide insight into both wildlife visitation behavior and which species are associated with higher pathogen contamination of produce fields. This information can be used by growers, landowners, and regulators to focus mitigation efforts on specific target areas or to implement mitigation efforts at specific points in time. Improving the efficiency of mitigation strategies will save time, money, and effort on preventing foodborne disease introduction by wildlife which may be a rare, but have large consequences. We believe this approach will allow for improving agricultural safety, public health and ecological well-being.