Posts Tagged: e.coli
E. coli and Salmonella are rare in wild birds, Campylobacter more common
Concerns over foodborne risk from birds may not be as severe as once thought by produce farmers, according to research from the University of California, Davis, that found low instances of E. coli and Salmonella prevalence.
While the research found that the risk is often low, it varies depending on species. Birds like starlings that flock in large numbers and forage on the ground near cattle are more likely to spread pathogenic bacteria to crops like lettuce, spinach and broccoli, according to a study of food safety risk and bird pathogens from the University of California Davis. In contrast, insect-eating species were less likely to carry pathogens.
The findings, published in the journal Ecological Applications, suggest that current practice of removing bird habitats around produce growers' farms over concerns the animals could bring foodborne pathogens into their fields may not solve the problem.
“Farmers are increasingly concerned that birds may be spreading foodborne diseases to their crops,” said Daniel Karp, the senior author on the study and an assistant professor in the UC Davis Department of Wildlife, Fish and Conservation Biology. “Yet not all bird species are equally risky.”
Only one foodborne disease outbreak in produce has been conclusively traced to birds: a Campylobacter outbreak in peas from Alaska. While the bacteria can cause diarrhea and other foodborne illness in humans, it's less of a concern to growers than E. coli and Salmonella, which have been responsible for multiple outbreaks across the nation.
In this study, researchers compiled more than 11,000 bacteria tests of wild bird feces and found that Campylobacter was detected in 8 percent of samples. But pathogenic E. Coli and Salmonella were only found in very rare cases (less than 0.5%).
In addition to the bacteria tests, researchers conducted roughly 1,500 bird surveys across 350 fresh produce fields in Western states and collected more than 1,200 fecal samples from fields. They then modeled the prevalence of pathogens in feces, interactions with crops, and the likelihood of different bird species to defecate on crops to determine risk.
Insect-eating birds pose lower risk
Based on the data, insect-eating birds, such as swallows, present a lower risk, while birds that flock near livestock, such as blackbirds and starlings, are more likely to transmit pathogens.
The data can help the agricultural industry determine risk and take action, such as separating produce crops from cattle lands. They also don't need to treat all birds the same.
“Maybe farmers don't need to be quite as concerned about all types of birds,” Karp said. “Our data suggest that some of the pest-eating birds that can really benefit crop production may not be so risky from a food-safety perspective.”
Removing habitat can backfire
This study and the authors' prior work indicate that removing habitat around farms may actually benefit the species that pose more risk and harm the beneficial, pest-eating ones that are less risky to food safety. This is because many prolific insect-eaters may visit crop fields to eat pests but need nearby natural habitats to survive. In contrast, many of the bird species that most commonly carry foodborne pathogens readily thrive on both cattle farms and produce farms without natural habitat nearby.
Insect-eating birds that forage in the tree canopy pose minimal threat because they are less likely to carry foodborne pathogens and come into direct contact with produce. They can also be valuable parts of the ecosystem, particularly if they eat pests that can harm crops. Installing bird boxes could attract the pest-eaters, as well as help with conservation efforts.
“We basically didn't know which birds were problematic,” said lead author Olivia Smith, a postdoctoral researcher at Michigan State University who was at University of Georgia when the paper was written. “I think this is a good step forward for the field.”
Additional co-authoring institutions include James Cook University, UC Berkeley, UC Riverside, University of Kentucky, University of Texas, Virginia Polytechnic Institute and State University, Washington State University, BioEpAr, The Nature Conservancy and Van Andel Institute.
The research was funded by the United States Department of Agriculture and the National Science Foundation./h3>/h3>/h3>/h2>
One of the events that attendees could sign up for was lunch with a scientist at The Ohio State University, located a few miles away from the conference venue. I chose Prof. Jeffrey LeJeune, an infectious disease microbiologist and epidemiologist, because a focus of his research is food safety, one of the topics included in the UC Global Food Initiative that UC President Janet Napolitano launched on July 1.
On the day of the luncheon, a Sunday, we were driven to The Ohio State University in buses the university provided. We assembled in the lobby of the Ohio Union (it was homecoming on campus and the Columbus marathon was in progress nearby), and were soon escorted to the tables of the scientists we had picked. The university kindly (and safely!) provided lunch.
At LeJeune's table, we introduced ourselves to one another. LeJeune began his presentation to his 15 guests by rebuffing the five-second rule. According to this rule, food dropped on the ground will not become contaminated with bacteria if it is picked up within five seconds of being dropped. LeJeune said it does not work. “Eating off the floor violates all food-borne illness prevention advice,” he warned.
Perhaps because we in his audience were all science writers, he proceeded to discuss communication challenges facing scientists. He said most of the emphasis in graduate training is on making discoveries, with hardly any attention paid to communicating these discoveries in lay language to benefit the general public. Other challenges he mentioned are the information explosion we are witnessing, resulting in deaf ears turned to many scientists' voices; and language barriers between scientists and journalists that hinder effective communication.
“The pasteurization of milk was a huge benefit to the health of the human population,” he said. “Most cheeses in the U.S. are pasteurized cheese products.”
We asked him many questions. He answered them all. He explained that the U.S. has the safest food supply. Despite this, pathogens can enter the food chain through live animals, he cautioned. Further, refrigeration could be inadequate. He said about 80 percent of food and vegetable contamination occurs post-farm. His tip for what to eat when traveling: “Avoid raw or unpeeled foods. It is best to choose what is fully cooked and hot.”
LeJeune noted there is no evidence to suggest that GM foods are problematic from a food safety perspective.
“There are some concerns for sure,” he said. “But these are largely economic or political. Nutrition-wise, GM foods can be beneficial. From a food safety and nutritional standpoint, I also see no significant differences between organic produce and non-organic or regular produce. There could be, however, some environmental impacts related to the different production systems.”
More questions followed. A discussion on E. coli bacteria gathered momentum, specifically how E. coli gets infected with a virus and how, when this virus decides to leave E. coli, it releases Shiga toxins, which, in turn, damage cells lining the kidney.
We were so engrossed in the discussion that it came as a surprise when one of the organizers of the luncheon strode into the room to inform us that our hour with the scientist was up and that the bus that had transported us to The Ohio State University was about to leave.
As we rose hastily from our chairs we thanked LeJeune for his presentation, which was clear and to the point – qualities all science (and other) writers appreciate. We know he had other topics to discuss with us: Can I cook my Jack-o'-Lantern after Halloween? (The answer is “Not if it sits out for more than two hours.”) And are raw diets for dogs a public health concern for humans? (The answer is “Your dog is more likely to have Salmonella if it is eating raw food.)
Although we didn't get to these topics, he left us with ample useful information about food safety. On the ride back to the conference, the bus was loud with conversation from the various lunch groups – what had been learned, how best it could be communicated, and how each one of us had made a new friend at the university.
Bart Weimer, professor in the UC Davis School of Veterinary Medicine, serves as director of the 100K Genome Project and co-director of the recently established BGI@UC Davis facility, where the sequencing will be done. Other collaborators include the U.S. Centers for Disease Control and Prevention and the U.S. Department of Agriculture.
The new five-year microbial pathogen project focuses on making the food supply safer for consumers. The group will build a free, public database including sequence information for each pathogen's genome — the complete collection of its hereditary information. The database will contain the genomes of important foodborne pathogens including Salmonella, Listeria, and E. coli, as well as the most common foodborne and waterborne viruses that sicken people and animals.
The project will provide a roadmap for developing tests to identify pathogens and help trace their origins more quickly. The new genome database also will enable scientists to make discoveries that can be used to develop new methods for controlling disease-causing bacteria in the food chain.
"This landmark project will revolutionize our basic understanding of these disease-causing microorganisms," said Harris Lewin, vice chancellor for research at UC Davis.
The sequencing project is critically important for tackling the continuing outbreaks of often-deadly foodborne diseases around the world. In the United States alone, foodborne diseases annually sicken 48 million people and kill 3,000, according to the CDC.
"The lack of information about food-related bacterial genomes is hindering the research community's ability to improve the safety and security of the world food supply," Weimer said. "The data provided by the 100K Genome Project will make diagnostic tests quicker, more reliable, more accurate and more cost-effective."
"We see this project as a way to improve quality of life for a great many people, while minimizing a major business risk for food producers and distributors," said Mike McMullen, president of Agilent’s Chemical Analysis Group.
A consumer-focused article about the project is available on the FDA website.
(This article was condensed from a UC Davis news release. Read the full press release and watch a video of Bart Weimer giving an overview of the project.)
Four years ago, a multi-state outbreak of E. coli O157:H7 in fresh baby spinach gripped the nation. Nearly 200 people in 26 states came down with the disease. Two elderly women and a 2-year-old boy died.
The outbreak was also devastating for the industry. The contaminated spinach was traced back to Central California, where growers produce 80 percent of the nation’s leafy greens. Scientists, farmers and regulators worked together to restore public confidence in products that are widely considered part of a healthy diet. Regulators and farmers created the California Leafy Green Marketing Agreement to establish a culture of food safety on leafy greens farms and researchers worked to close gaps in the body of scientific knowledge about the sources of E. coli O157:H7 in the region.
In 2006, UC and USDA researchers were already designing a four-year study of the possible sources of E. coli O157:H7 near Central California fresh produce fields when the high-profile spinach outbreak occurred. This month, data collection from rangeland and farmland, steams and irrigation canals comes to a close. The team of scientists is now analyzing the data to reach conclusions that will help prevent future food contamination.
Preliminary results reflect a diversity of E. coli O157:H7 carriers near Central Coast farms, according to Edward (Rob) Atwill, a UC Davis School of Veterinary Medicine specialist in waterborne infectious diseases and co-principal investigator of the study. Early on, free-ranging feral swine were implicated as carriers of the deadly bacteria, but it wasn’t known whether there were other sources in the environment. The researchers collected 1,233 samples of wild and feral animal scat from 38 Central Coast cattle ranches and leafy greens farms that were adjacent to riparian, annual grassland and oak woodland habitat. Eighteen of the samples were found to contain E. coli O157:H7.
The scientists found the bacteria in
- 3 of 60 brown-headed cowbirds
- 5 of 93 American crows
- 2 of 95 coyotes
- 1 of 72 deer mice
- 10 of 200 feral swine
E. coli O157:H7 was not found in scat samples from deer, opossums, raccoons, skunks, ground squirrels, or other bird and mouse species.
“Our goal over the next nine months is to finish analyzing this very large and comprehensive dataset and to identify various good agricultural practices that reduce the risk of foodborne pathogens for the produce industry,” Atwill said.
Research helps prevent contamination of fresh leafy greens.
Although the outbreak earlier this month of E. coli O145 in shredded Romaine lettuce hasn’t touched California consumers and local retailers, it is impacting the industry. Once again, the safety of pre-washed and cut leafy vegetables are in headlines, raising the fears of consumers and producers alike.
The Centers for Disease Control have confirmed 23 illnesses and 7 probable illnesses in New York, Michigan, Ohio and Tennessee from the contaminated lettuce. The traceback investigation is stretching west to Yuma, Ariz., where the lettuce may have been grown. So far, the source of the contamination has not been identified.
A source of confusion and alarm, however, is the contaminant’s O145 designation. For the past 30 years, the majority of the E. coli illness outbreaks in America were serotype O157:H7. UC Davis Cooperative Extension produce safety specialist Trevor Suslow said E. coli O145 doesn’t come completely out of the blue. O145 is recognized in its association with food in other countries and more often with animal products, not produce.
Suslow and his staff were well aware of E. coli O145 prior to this month’s outbreak and included it in their recent research aimed at development of a new method for detecting a broad range of the most dangerous E. coli bacteria in produce and produce production environments.
The new test was not designed to identify a particular strain of E. coli, but to determine whether a pathogenic/toxigenic strain of E. coli – such as O145 – is present. If the test comes up positive, a secondary test can be conducted to narrow down the specific type of E.coli.
Pathogenic/toxigenic E. coli are of tremendous concern for the fresh produce industry. “Generic” E. coli live in the guts of most mammals; they are typically harmless and may even be beneficial. However, pathogenic/toxigenic E. coli, when ingested by humans, can cause bloody diarrhea and, particularly in the very young and very old, may lead to kidney failure and even death.
Suslow said the new test, which goes by the working name “total pathogenic E. coli,” or TPEC, was tested in a variety of different types of samples: irrigation water, feed lot surface material, manure, compost, soil and produce.
“With all those materials, we had very good effectiveness, but especially with water and produce,” Suslow said.
The research will be presented at the UC Davis Center for Produce Safety Produce Research Symposium on June 23. The Produce Research Symposium is open to the public. A $150 registration fee includes all symposium sessions, breakfast, lunch and an evening reception in the courtyard and gardens of the Robert Mondavi Institute for Wine and Food Science.
For more information or to register for the symposium, see the Center for Produce Safety website at http://cps.ucdavis.edu.
Bagged lettuce was implicated in a recent food safety outbreak.