Reducing E. coli O157:H7 Contaminated Cattle Leaving the Farm for Slaughter

We continue to hear about food borne sickness outbreaks caused by the pathogen E. coli O157:H7 (O157). The most serious form of sickness from this organism is haemolytic uremic syndrome (HUS), a disease characterized by kidney failure which can result in death, especially in young children.

The chances of O157 causing sickness are greater from eating undercooked contaminated beef products, consuming contaminated ready to eat fruits and vegetables or drinking contaminated water than from properly cooked products. Carriers of the O157 pathogen can be livestock, wildlife, birds, pets and even other humans, but by far the biggest culprit for harbouring the pathogen is cattle.

Cattle that harbour, or have O157 "colonize", in their digestive tracts show no signs of any type of sickness and their production performance is not affected. Producers have no idea their animals are shedding the pathogen unless fecal samples from their herd are tested, which is expensive and not practical. Studies have shown that if testing was carried out on each herd many times over a one year period O157 shedders will be found. Prevalence of shedding has seasonal and stress period effects. For example shedding goes up when animals are stressed at weaning. Therefore, every farm manager should assume they have some O157 pathogens in the manure produced from their cattle.

It is important to know that even if an animal has O157 colonized in its digestive tract, the meat and muscle of that animal does not harbour the pathogen. O157 contamination in food and water is the result of cross-contamination of pathogens from feces. When beef, especially hamburger, becomes contaminated it is due to cross-contamination at the meat processing facility during slaughter from contact of the carcass with the hide or the contents of the intestines. Packing plants have installed several intervention methods in the slaughter process to help control O157 but they are not absolute, which leads to some pathogens surviving the process.

Figure 1. Minimizing the amount of manure tag on feedlot animals is the first step in reducing E. coli.

Farm managers can do their part in helping to control O157 by reducing the pathogen load on hides and in the guts of cattle leaving the farm before traveling to the packing plant. In order to reduce the O157 pathogen load, here are some pre-slaughter interventions to implement:

Adopt a vaccination program for O157 reduction

Canada now has an approved vaccine developed by Bioniche Life Sciences Inc. called Econiche(TM) that will reduce O157 shedding. Consult your herd veterinarian about a program. This will reduce the total amount of O157 in the farm environment.

Keep watering sources free of manure

Water sources can be a vector for spreading O157 from animal to animal. Ensure water bowls/troughs are drained and cleaned after being soiled by cattle feces.

Equipment used for handling feed and removing manure

Equipment, like the water sources, can be a vector for spreading O157 from animal to animal. If the same loader is used to move manure as well as feed it should be thoroughly cleaned between uses. If that is not possible there should be equipment designated for either feeding or manure handling, never both.

Use adequate bedding to keep hides free of excess tag

Market cattle with excess tag are a high risk carrier for O157 at slaughter. The risk of contamination to the meat can occur in two ways, first when the knife used to split a hide passes through tag it carries contamination into the carcass. Second, when the hide is pulled in the very moist environment of the kill floor, tag particles easily become airborne with the potential to cross-contaminate all surfaces they come in contact with. Use of adequate bedding is therefore very important in the housing area to prevent tag accumulation on hides.

Preparing cattle for shipping to slaughter

Shrink cattle for 12 to 24 hours before shipping. Reducing gut fill helps reduce manure excreted in holding pens, when loading on trucks and during trucking. Use low stress cattle handling techniques. Calm cattle excrete less manure.

Clean trucks

Load cattle onto clean trucks with clean, adequate bedding. This will help prevent hides being contaminated with pathogens from previous loads of cattle transported with the truck.

By following these practices the O157 pathogen load on and in market cattle will be reduced when cattle arrive for slaughter. Along with the interventions put in place by the packers, these steps will collectively reduce the probabilities of contaminated end product, which translates to fewer cases of food borne illness caused by O157.

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