Dr. Jeffrey LeJeune
Ohio State University
Cattle manure can harbor bacteria, viruses and parasites that can cause illness in humans. Since the first outbreak of E coli 0157 in 1982, this bacteria infects 70,000 people in the US each year with approximately 10% of those infected experiencing renal failure. With only a very small infectious dose (~100 CFUs) needed to affect humans, outbreaks have been associated with undercooked beef, non-pasteurized milk and cider, fruits and vegetables, drinking water, lake swimming, and both animal and human contact. Although cattle are not the reservoir for E coli 0157 and are asymptomatic, they can amplify the organism shedding up to 1 million human infectious doses per day in fresh manure. While only a small percentage shed at this rate, they contribute to 80% of the total. Analysis of four herds indicates point sources, such as watering troughs or feed, for infection and greater prevalence from July to September which is also reflected in human trends. E coli 0157 can remain infectious for up to 250 days in non-sterile water, more than 6 months on surfaces such as concrete and straw and more than 1 year in manure piles. Composting has the potential to destroy the organism if temperatures of 55 degrees Celsius are maintained for at least 24 hours. Although E coli 0157 will never be eradicated, additional research is needed to understand the ecology of the organism in the farm environment and gastrointestinal tract of cattle and to develop handling procedures that minimize the risk to humans. Areas of investigation include minimizing infection from feed, field testing probiotics to inhibit growth and developing vaccines to protect against gastrointestinal colonization.
Discussion:
Steve Loerch (OSU) asked if the specific source of the corn and barley associated with contamination and been checked prior to feeding it to cattle. LeJeune noted that it was not feasible to test before feeding due to the large number of shipments.
Brian McSpadden-Gardner (OSU) questioned whether the seasonal fluctuation of the organism could be attributed to the susceptibility of the host or to survival in the environment. LeJeune responded that, while there may be variations in the animal’s susceptibility with the seasons, none has been identified. Analysis of soil and other environments such as sawdust bedding do show higher counts during the summer.
Ted Short (OSU) asked about the treatment for humans infected with E coli 0157. LeJeune responded that for those with symptoms (bloody diarrhea), increased fluids are recommended. Antibiotics are contraindicated and may increase the amount of toxin produced by the bacteria. Children and the elderly are most susceptible to contamination and development of renal failure.
Loerch questioned whether the sterile environment created by human’s sanitation efforts impacts contamination. That is, is there more immunity among farm families that have a greater potential for contact with the pathogen? LeJeune noted that research is just beginning to explore the relationship between immunity and exposure.
Short asked if swine or poultry are susceptible to E coli 0157. LeJeune observed that pigs get a different disease from a different E coli. The distribution of receptors affect whether the animal becomes sick or not. E coli 0157 has only recently been detected in swine but is very rare. Neither pork nor sausage has ever been implicated in an outbreak. E coli 0157 is not found in poultry.
Loerch asked if there is the potential to test for E coli 0157 as a screening procedure at the slaughterhouse. LeJeune responded that it is not feasible as such testing would result in a large number being culled, negatively impacting marketability.
Jim Skeeles (OSU Extension) asked if county fair boards should adopt policies to minimize the risk of contamination. LeJeune identified two safety precautions: 1) wash hands and 2) only consuming food outside animal barns. Hand washing can reduce risk of contamination by 50% and those consuming food in barns increase their risk by about 20 times.
Notes by Mary Wicks
The OCAMM (Ohio Composting and Manure Management) Program is funded by OARDC/OSU.