Study Looks at Wild Birds' Impact on E. coli Spread on Farms

September 20, 2007

WOOSTER, Ohio — Ohio State University scientists are using a $1 million U.S. Department of Agriculture (USDA) grant to study the relationship between wild birds and E. coli contamination on farms, in an effort to gather crucial data leading to effective pre-harvest control strategies that would help minimize foodborne illnesses throughout the country.

Jeff LeJeune, a microbiologist and veterinary scientist with the university’s Ohio Agricultural Research and Development Center (OARDC) in Wooster, leads the groundbreaking study, which concentrates on an invasive nuisance bird whose impact on the propagation of disease-causing pathogens has not been determined: European starlings.

Yet, LeJeune said, there’s strong evidence that these birds harbor E. coli and other dangerous organisms such as Salmonella and Campylobacter, and that they contribute to the spread of pathogens between farms. Studies conducted by his lab have found that E. coli O157-H7 strains isolated from European starlings are the same as strains found on dairy farms in close geographical proximity.

“This is the first study about the relationship between European starlings and food safety,” said LeJeune, also a specialist with OSU Extension. “We need to know how much these birds are contributing to infection on farms to see if management strategies to reduce their numbers or restrict access to livestock-feeding areas are warranted. If you can prevent infection on the farm, you’ll positively impact food safety downstream.”

Although many different species of wild birds can potentially carry foodborne illnesses and contaminate animals or crops via feed, water or soil, European starlings are in a category of their own.

First introduced in the United States in 1890 with the romantic notion of populating New York City’s Central Park with every bird mentioned in Shakespeare’s works, the aggressive, strong-flying starlings have spread throughout the country and grown to an estimated 140-200 million individuals.

“European starlings are known to displace native cavity-nesting birds, knock out power lines, dirty buildings in the cities and threaten aircraft safety,” said Jeff Homan, a USDA research wildlife biologist working in the study. “And they love to congregate by the thousands at feedlots and dairy farms attracted by feed, which causes important economic losses to producers and affects animal growth and milk production.”

Ohio is a perfect location for this study, Homan said. The Buckeye state has one of the highest breeding densities of European starlings in the United States, with large winter roosts containing 400,000-600,000 birds. The project targets Wayne County in northeast Ohio, home to at least one large European starling roost and numerous dairy farms.

“Cattle are an important foodborne route of human infection with E. coli via contaminated ground beef and raw milk, and manure is an important environmental source of contamination, which is why we are concentrating our study on dairy farms,” LeJeune explained. “But this research will also be important to find out whether starlings are contributing to the spread of E. coli on vegetable fields as they fly between dairy farms.”

According to the U.S. Centers for Disease Control and Prevention (CDC), E. coli O157:H7 (one of hundreds of strains of the bacterium Escherichia coli) causes an estimated 73,000 cases of infection and 61 deaths in the United States each year. Most of these cases are associated with eating undercooked ground beef, but a growing number of recent E. coli-related outbreaks and recalls have involved fresh vegetables — including the California spinach outbreak that sickened 199 people and killed three last year.

To determine the extent to which European starlings disseminate E. coli between cattle on neighboring farms, LeJeune and Homan are using bird-tracking technology and DNA testing of E. coli subtypes.

Fifty starlings from five different dairy farms will be captured and fitted with tiny tail-mount radiotelemetry transmitters, which can track the movement and behavior of each bird — including the farm(s) they visit and how long they stay. As many as 2,000 other birds will be tagged with 5-inch leg flags of different colors to supplement the telemetry studies.

“We are asking farmers and the general public in Wayne and surrounding counties to let us know when and where they spot any of these tagged birds ” LeJeune said. “This will help us get a better picture of their flying behavior and bird distribution in the area.”

The telemetry studies will be complemented by laboratory work, including the analysis of molecular subtypes of E. coli found in starlings, animals and on different farms. All of this data will help researchers make correlations between the movement and behavior of birds and the presence of specific E. coli subtypes in different environments they visit — looking for patterns of where the presence of E. coli overlays between bird movement and farm locations.

Other objectives of the study include determining the frequency of cattle exposure to E. coli-contaminated starling feces and the relative contribution of large on-farm starling populations to the prevalence of E. coli on dairy cows. University of Guelph (Ontario, Canada) veterinary epidemiologist David Pearl is also involved in the study.

If you see a European starling sporting a color flag on its leg, please report the sighting by logging on to http://oardc.osu.edu/starling; e-mailing o157@osu.edu; or calling (330) 263-3619.

OARDC and OSU Extension are the research and outreach arms, respectively, of Ohio State’s College of Food, Agricultural, and Environmental Sciences.

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Author(s): 
Mauricio Espinoza
Source(s): 
Jeff LeJeune