Wildlife survey for E. coli O157:H7 in the central coastal counties of California

We propose to continue testing wildlife for the human pathogenic strain of bacteria, Escherichia coli O157:H7 in Monterey, San Benito and San Luis Obispo Counties. Since 1995, this pathogen has resulted in more than 25 outbreaks from eating leafy green vegetables (LGV); approximately half of these have been associated with LGV grown on the California central coast. Wildlife has been suggested to be a source of E. coli contamination of LGV. Because of this uncertainty, farmers are being required to build deer- and wild pig-proof fences around their fields, and remove habitat and wildlife from their farms. To date, however, there is minimal definitive data that wildlife are an important source of contamination. We propose to collect colon or fresh fecal samples from wildlife collected in relevant LGV production areas to determine if they are carrying E. coli O157:H7. This information will help us better manage and protect wildlife and provide food health safety information to farmers and to the food industry. The future of sustainable wildlife populations in the three central coastal counties is dependent on having cumulative and accurate scientific data to properly manage wildlife and to protect human health.

In 2006, human pathogenic strains of Escherichia coli O157:H7 (EcO157) were isolated from non-native wild pigs in San Benito County. EcO157 can cause serious health problems in people. However, to date, minimal data exist to determine if wildlife are a true source of contamination. We propose to collect samples to determine if wild animals are carrying EcO157. With better knowledge about the spatial and temporal incidence of EcO157 in local wildlife, we will provide accurate data for growers, landowners, processors and auditors in order for them to make decisions that will balance food safety concerns with wildlife management. The results will assist resource agencies and growers in developing strategies, and management plans and policies for preventing crop contamination in the fields to protect public health and to protect wildlife and their habitats. The purpose is to bring practical science and farm practice to the farming and ranching communities. This will help us better manage and protect wildlife and for agencies to develop policy and wildlife management plans to reduce the food safety wildlife uncertainty. The coastal county area has been divided into watersheds using Department of Water Resources watershed maps. The reasoning for a watershed-based landscape is that EcO157 is believed to wash down watersheds, most animals will have lived most of their life within a particular watershed, and land ownership does not need to be identified. We propose to collect colons or anal swabs from birds, small mammals, wild pigs, and deer. If provided the opportunity by landowners, we will collect samples from elk, geese, and ducks; some samples will be obtained at public sites. Small birds will be captured using mist nets and small mammals will be captured using live-box traps and released. We plan to coordinate with landowners or with USDA - Wildlife Services to collect colons from wild pigs during depredation hunts and trapping. All samples will be analyzed by USDA-ARS-WRRC or UC Davis – Western Institute for Food Safety and Security (WIFFS) laboratories by methods reported previously by Cooley 2007 and Jay 2007. The results will be forwarded to Dr. Rob Atwill at UC Davis for further statistical analysis and publication. Because of the sensitivity of this issue, landowners do not want to be identified. As such, UC Davis has developed a sampling location coding system, so land ownership can not be identified by laboratory staff and the results are not available to field staff. The analyzed results will be published based on a large geographical scale, such as watersheds or by county, thus preventing identifying individual land ownership. We are networking with both public and private landowners to seek voluntary permission to allow us to collect samples discreetly and confidentially the next 2 years. To date, we have access permission to over 14 properties, plus we continue to make contact with other land owners.

We collected samples from nine geographical regions (i.e., watershed) within three California central coastal counties to develop conclusive results regarding which species of wildlife are a significant or insignificant risk to produce safety. We collected fecal samples to determine if wild animals are carrying human pathogenic strains Escherichia coli O157:H7 and Salmonella. This information will help the produce industry better manage and protect wildlife and provide food health safety information to farmers and to the food industry, and for agencies to develop policy and wildlife management plans to reduce the food safety wildlife uncertainty. The future of sustainable wildlife populations is dependent on having cumulative and accurate scientific data to properly manage wildlife and to protect human health. The purpose is to bring practical science and farm practice to the farming and ranching communities. 

Project tasks: 
1: network with landowners; 2: Trapping and netting; 3: hunter check stations; 4: trap geese; 5: lab analysis

The prevalence of E. coli O157:H7 and Salmonella appears to be low in native wildlife and is highest in non-native wild pig. Comparing this study to other California food safety-wildlife studies, the overall prevalence for E. coli O157:H7 and Salmonella tends to be less than 2% and around 5%, respectively, in native wildlife. An E. coli O157:H7 outbreak occurred in strawberries in northern Oregon during the summer 2011. Deer have been implicated as a source for this outbreak. Farmers in the Yuma Valley, Arizona, are also concerned about deer as a potential risk to food safety. We recommend big game continue to be surveyed across the state for human pathogenic bacteria. Other studies indicate blackbirds that occupy Confined Animal Facilities, such as stock yards have a slightly higher E. coli O157:H7 prevalence than this study. High density flocks utilize these facilities and move out to agricultural areas to feed, thus being a potential vector to crops. As such we recommend blackbirds be surveyed for human pathogens in and nearby Confined Animal Facilities. Geese also form large concentrations on agricultural fields and roost on sewage treatment ponds, thus geese should continue to be surveyed. We tested only for two major pathogenic types of bacteria, thus we recommend other pathogenic strains associated with outbreaks or recalls of fresh produce (e.g. non-O157 Shiga toxin producing E. coli, Listeria monocytogenes) be included in future wildlife studies. Thus, we recommend funding big game, bird species that form large density flocks around agricultural facilities, and goose studies be continued.