Control Measures for E. coli 0157:H7 at the Producer level

By Clifton L. Willms, Ph.D., PAS

An excellent review of scientific literature was published in the March 2001 issue of ARPAS dealing with control measures of shiga-like toxin-producing Escherichia coli (including 0157:H7) to assure beef safety. The review dealt with several factors related to this issue including the incidence and pre- and post-harvest control measures.

The point of this article is to highlight the factors emphasized in the review that cattlemen can manage during the production phase. As cattle producers, we cannot do very much about post-harvest control measures. But, we can implement management techniques that help reduce the incidence of E. coli 0157:H7 infection in live animals and do our part in providing a safe and wholesome food product to the consuming public.

Cattle are a transient carrier of E. coli 0157:H7

Fecal shedding of the pathogen has not been associated with any known cattle disease.
Fecal shedding of E. coli 0157:H7 is most common in warm weather (summer).
Young animals are more susceptible to colonization by the pathogen.
Newly arrived feedlot cattle have exhibited threefold higher prevalence rate than those in the feedlot for several months. 
This could be due to newly arrived cattle being younger or to a compromised immune system.
Definitive evidence of E. coli 0157:H7 colonization and attachment in the bovine gastrointestinal tract and infection under natural conditions has not yet been reported. Animals acquire the pathogen in their gastrointestinal tract from environmental sources such as manure in feed and water contamination with E. coli 0157:H7.
The pathogen is widely distributed among cattle throughout the U.S. but at a low prevalence rate.

Control measures during the production phase:

Manure application to pastures has been associated with infection of E. coli 0157:H7 in grazing cattle. Consumption of ruminant manure is a key risk factor for infection.
E. coli 0157:H7 has a high tolerance to a variety of environmental conditions.
E. coli 0157:H7 incubated at low or high temperatures are still capable of producing toxins.
E. coli 0157:H7 has survived –20 C (-4 F)in cattle feces and 4C (39 F) in sheep feces for at least 100 days. E. coli 0157:H7 incubated at 5, 22, and 37 C (41, 72, and 99 F, respectively) survived for 70, 56, and 49 days, respectively.
E. coli 0157:H7 has survived in a manure pile under fluctuating environmental conditions for 21 months.
Appropriate manure handling is critically important to minimize the spread of E. coli 0157:H7. Extended periods between manure application and grazing or harvesting forage is recommended. (CLW editorial: Or eliminate manure application on pastures and incorporate manure into soil used for forage production.)
Drinking water has been a common source of contamination.
Because cattle consume large quantities of water at a time, infrequent cleaning of water troughs can promote E. coli 0157:H7 reinfection.
No evidence exists to suggest that E. coli 0157:H7 has acquired resistance to antibiotics or that probiotics are effective in prevention of infection.
Since the identification of E. coli 0157:H7 as a food born pathogen (1982) somewhat coincided with the wide spread adoption of ionophores in feedlot cattle diets (late 1970s), ionophores have been implicated as enhancing the establishment of the bacteria in the intestinal microbial population. Critical evaluation of this concern has not proved such an association.
None of the probiotics available for cattle in the U.S. have met the regulatory requirements to demonstrate that they are useful in protecting the colonization of E. coli 0157:H7 bacteria in cattle.
Fecal contamination of feed ingredients is a major risk factor.
Regular cleaning of feed bunks is suggested as a management practice that will prevent or minimize on-farm multiplication of E. coli 0157:H7.
It is hypothesized that nutrient dense, low fiber diets induce a lower incidence of transmission and(or) shedding of fewer E. coli 0157:H7 cells but do not induce the clearance of the pathogen from the gastrointestinal tract. Conversely, feeding diets high in fiber and low in nutrient density, and briefly withholding feed, induce shedding of large numbers of E. coli 0157:H7 and(or) increase the susceptibility to new infections. But, both low nutrient density diets and short term feed withholding induced elimination of the pathogen. This is consistent with in vitro data indicating E. coli 0157:H7 grows well in rumen fluid from fasted cattle while its growth is restricted in rumen fluid from well-fed cattle.
Cattle may shed large numbers of E. coli 0157:H7 in their feces when not fed regularly.
E. coli 0157:H7 isolates grew poorly or their growth was inhibited in rumen fluid collected from cattle receiving a high-energy diet.
Well-fed cattle are less susceptible to become reservoirs of pathogens like E. coli 0157:H7.
Rumen fill of cattle per se is not associated with fecal shedding of E. coli 0157:H7.

The above points underscore the application of common sense sanitation and bunk management procedures in a feed yard with a quality assurance mindset. It also underscores the need to think ahead about some of our fertilization and management practices related to forage grazing and production. The emphasis that Land O' Lakes Farmland Feed has placed on good bunk management and attention to detail in feedlot cattle to improve feed efficiency and reduce digestive disorders can also help provide consumers with a safe, wholesome product.

Reference: Hussein, H. S., S. L. Lake and T. P. Ringkob. 2001. Review: Cattle as a Reservoir of Shiga-Like Toxin-Producing Escherichia coli Including 0157:H7 – Pre- and Post Harvest Control Measures to Assure Beef Safety. ARPAS 17:1.

Back Home Up Next