Frequently Asked Questions about EHECshort forenterohemorrhagic Escherichia coli

Generally speaking, humans become infected with EHECshort forenterohemorrhagic Escherichia coli via the oral route. The most frequent route of infection is the consumption of food contaminated with EHECshort forenterohemorrhagic Escherichia coli, mainly raw milk and meat products. EHECshort forenterohemorrhagic Escherichia coli occur frequently in livestock (cattle, sheep, goats, less frequently pigs) without the animals becoming sick. The pathogens migrate from the animals’ intestinal flora to foods of animal origin (e.g. milk and meat).These foods can become contaminated with EHECshort forenterohemorrhagic Escherichia coli at almost any point along the production chain down to the consumer. It only takes a few germs to infect people. In the case of EHECshort forenterohemorrhagic Escherichia coli O157:H7 people can become ill after ingesting only 10-100 germs.

Other important routes of infection are: contact with EHECshort forenterohemorrhagic Escherichia coli carriers (sick people and healthy livestock who excrete these pathogens) and infections contracted from an environment contaminated with EHECshort forenterohemorrhagic Escherichia coli (e.g. surface water, earth). In some cases, the pathogens can survive for several weeks in the environment. Fruit and vegetables may also be contaminated with EHECshort forenterohemorrhagic Escherichia coli from water itself contaminated with EHECshort forenterohemorrhagic Escherichia coli and through the application of excrement-containing fertiliser. If this food is not properly washed prior to consumption, it can become a source of infection for man.

The Robert Koch Institute regularly publishes the latest figures on cases of disease on its website.

Within BfRshort forGerman Federal Institute for Risk Assessment and the Robert Koch Institute there are reference laboratories which are involved in the identification, typing and risk assessment of EHECshort forenterohemorrhagic Escherichia coli. BfRshort forGerman Federal Institute for Risk Assessment staff type E. coli from food sent in by the food control authorities of the federal states in order to identify human pathogenic (i.e. which can make people sick) EHECshort forenterohemorrhagic Escherichia coli. It is necessary to determine the EHECshort forenterohemorrhagic Escherichia coli types and their virulence properties in order to ascertain whether human infections can be traced back to the consumption of food contaminated with EHECshort forenterohemorrhagic Escherichia coli and to contain outbreaks of the disease as quickly as possible.

In food the variants of E. coli which are suspected of being EHECshort forenterohemorrhagic Escherichia coli germs are examined. They are called VTECshort forVero toxin-producing E. coli/STECshort forShiga toxin-producing Escherichia coli (Shiga toxin and verotoxin producers). The federal states pass on the examination results on the incidence of VTECshort forVero toxin-producing E. coli/STECshort forShiga toxin-producing Escherichia coli in meat samples from wild-living animals every year to the Reference Laboratory for the Epidemiology of Zoonoses within BfRshort forGerman Federal Institute for Risk Assessment. During the period 2002-2006 between 80 and 160 samples of meat from wild-living animals were examined annually for the presence of these germs. The incidences of positive detections during the same period were between 3 % and 25 % in meat from wild-living animals and 5 % for beef. In 2006 VTECshort forVero toxin-producing E. coli/STECshort forShiga toxin-producing Escherichia coli were found in 10 % of the meat samples from wild-living animals examined. As the numbers of samples are relatively small and the term "meat from wild-living animals" encompasses various species of animals, this assessment is not easy. What is, however, noticeable is that in recent years the E. coli serovars isolated relatively frequently from meat from wild-living animals have also been identified in EHECshort forenterohemorrhagic Escherichia coli cases in humans (O26, O146). In beef samples, however, these samples were only found in isolated years or not at all.

Surveys by BfRshort forGerman Federal Institute for Risk Assessment revealed that EHECshort forenterohemorrhagic Escherichia coli have been identified more frequently in meat samples from wild-living animals. This applies in particular to meat and meat products from red deer as these animals, like other ruminants, may carry EHECshort forenterohemorrhagic Escherichia coli as part of their intestinal flora.

A research project by the National Reference Laboratory for Escherichia coli within BfRshort forGerman Federal Institute for Risk Assessment aims to clarify whether there is a possible association between EHECshort forenterohemorrhagic Escherichia coli in wild-living animals, in meat from wild-living animals and EHECshort forenterohemorrhagic Escherichia coli cases of disease. The focus is on the following questions:

• Are wild-living animals an original EHECshort forenterohemorrhagic Escherichia coli reservoir and can livestock become infected through direct contact or indirectly via the environment, e.g. through contaminated pastures, feed troughs and water?
• Do the EHECshort forenterohemorrhagic Escherichia coli detected in wild-living animals belong to the serotypes which have already been linked to cases of human disease?
• Is meat contaminated with EHECshort forenterohemorrhagic Escherichia coli from wild-living animals an important source of infection for man?

This leads on to the question whether the incidence of EHECshort forenterohemorrhagic Escherichia coli in meat from wild-living animals can be attributed to inadequate hygiene measures during the production and processing of meat from these animals.

In order to find answers to these questions, the research project will compare the EHECshort forenterohemorrhagic Escherichia coli strains isolated from meat from wild-living animals, wild-living animals, pets and humans. The method involved is very complex. It could, however, provide insight into whether, for instance, EHECshort forenterohemorrhagic Escherichia coli O157:H7 that frequently occurs in man is also found in livestock and in wild-living animals and, if this is the case, in which animal species in particular. Prevention strategies could be established on the basis of these findings with a view to reducing the risk of human EHECshort forenterohemorrhagic Escherichia coli infection in the medium term.

Thoroughly cooking food kills the pathogens and the toxins produced by them. A minimum core temperature of 70°C must be reached and maintained for more than 2 minutes. The following principle applies to the preparation of raw foods of animal origin like meat, raw milk and eggs in the kitchen. These foods should not come into contact with foods consumed raw (like salad), or into indirect contact with hands, knives, chopping boards or other kitchen utensils. If this happens, then these foods can themselves become a source of infection with EHECshort forenterohemorrhagic Escherichia coli or other pathogens.