- Campylobacter jejuni - An estimated 2 million cases per year with the principal vehicles being poultry and unpasteurized milk. Salmonella spp. - An estimated 1.5 million cases per year with the principal vehicles being eggs, poultry, beef, pork and produce. E. coli O157:H7 - An estimated 60,000 cases per year with the principal vehicles being cattle (handling) and beef, produce and water (both recreational and drinking).

Transmission of Foodborne Pathogens - Carried in the intestinal tract of cattle, E. coli O157:H7's most frequent origin is direct or indirect contact with cattle manure. Manure can contaminate food when used as a soil fertilizer, when it pollutes irrigation water and when cattle defecate near produce or foods of animal origin. Campylobacter jejuni and Salmonella spp. are carried in the intestinal tract of poultry and other animals. Fecal contamination of skin occurs during poultry and livestock grow out and processing.

Prevalence of Risk Factors for Foodborne Illnesses in the General Population - Approximately 7,500 adults in California, Connecticut, Georgia, Minnesota and Oregon were interviewed by telephone between June 1996 and June 1997. The interviews revealed that 30 percent ate pink hamburger, 18 percent ate running eggs, 1.9 percent ate raw shellfish, 1.5 percent drank raw milk, 7 percent did not wash cutting boards after cutting raw chicken, and 7 percent did not wash their hands after handling raw meat or poultry.

Risk Factors for Sporadic Campylobacter Infections in the U.S. - A case-control study of six FoodNet sites involving 1463 patients with Campylobacter infection and 1317 controls was conducted from January 1998 to March 1999. The risk factors revealed by the study include foreign travel, eating undercooked poultry, eating chicken, turkey or nonpoultry meat cooked outside the home, eating raw seafood, drinking raw milk, living on or visiting a farm, having contact with farm animals or puppies.

Risk Factors Associated with Sporadic Cases of E. coli O157:H7 Infection...
In the U.S. - In 1998, the U.S. Centers for Disease Control and Prevention reported these risks to be eating undercooked ground beef and visiting farms.
In Scotland - These risks include handling or preparing raw food (40%), gardening or garden play (36%), living on or visiting a farm (20%), direct or indirect contact with animal manure (17%), private water supplies (12%), and recent failures with high coliform counts of water supplies (12%).
In Sweden - The risks are contact with farm animals and farms. The Swedish Government recommends between June 1 and October 31, farmers with cattle, sheep or goats should avoid allowing unauthorized people (especially children under the age of five) to visit the animal houses and have contact with cattle, avoid consumption of unpasteurized milk and dairy products, and avoid contact between grazing animals and people sunbathing on beaches.

The Manure Glut: A Growing Environmental Threat - Five tons of animal manure is produced annually for every person living in the United States. The amount of animal manure produced is 130 times greater than the amount of human waste produced. Cattle, hogs, chickens and turkeys produced an estimated 1.36 billion tons of manure in 1997.

Where Must Food Safety Begin? - Solutions are complex, but must begin at the farm. Food producers must consider and treat their products as foods rather than as commodities. Control points include using beneficial microorganisms that prevent colonization or eliminate pathogens from animals used for food. Control points also include competitive exclusion bacteria (probiotics) bacteriophage, innovative vaccines and dietary and feeding practices.

A Look into the Future - Controlling E. coli O157:H7...
By Competitive Exclusion Bacteria - Competitive exclusion involves the use of
microbial cultures that out-compete pathogens from colonizing specific niches. Three strains of E. coli that produce metabolites inhibitory to E. coli O157:H7, and thrive in the same sites of the gastrointestinal tract of cattle as E. coli O157:H7, can effectively reduce or eliminate within 2 weeks fecal shedding of E. coli O157:H7 by cattle.

By Bacteriophage Treatment of Calves - Six bacteriophage capable of lysing most E.coli O157:H7 strains were orally administered to six-week old calves. By the second, fourth and sixth days, phage-treated calves shed fewer E. coli O157 than calves fed only E. coli O157 and no E. coli O157 was shed after the eighth day. Four of five calves fed E. coli O157 shed O157 for 10 to 16 days.

By Vaccination - Traditional approaches to vaccinate cattle against E. coli O157:H7 are not likely to be successful. Innovative vaccines may be useful; for example, insert genes of virulence factors of E. coli O157:H7 into alfalfa to stimulate production of IgA in GI tract. As an example, edible vaccines are being developed for humans. Potatoes were genetically engineered to produce B subunit of E. coli heat labile (LT). enterotoxin. Ten of 11 volunteers who ingested the potatoes had a four-fold increase in serum (IgG) antibodies to LT and six of 11 had a four-fold increase in intestinal (IgA) antibodies to LT.

By Farm Management Practices - Farm water troughs are sources of E. coli O157 contamination from cattle manure and cud. Frequent cleaning and improved design of cattle water reservoirs are needed to reduce contamination.

By Cattle Diet - Test steers were fed diets of grain, alfalfa and Timothy grass. E. coli O157:H7 was administered into their rumens three weeks after diet adaption. The average duration of fecal shedding of E. coli O157:H7 was four days for cattle on grain diet, 39 days for cattle on alfalfa diet and 42 days for cattle on Timothy grass diet. In a similar study, cattle were fed rations of grain or hay in two- to three-week increments or solely grain or hay. Irrespective of the feeding regime, Shiga Toxin-Producing E. coli excretion was significantly reduced during the first week after changing the feed. Thereafter, excretion increased.

Article by Dr. Mike Doyle, University of Georgia Center for Food Safety. Phone: (770) 228-7284