Animals as a source of infections for humans - diseases caused by EHEC

EHEC (enterohaemorrhagic E. coli) bacteria are new, only since 1982 recogni zed zoonotic pathogens. EHEC differ from E. coli intestinal commensales by the fact that they are lysogenic infected with bacteriophages, which carry the genetic information for the production of shigatoxins (Stx type 1 and/o r 2). Due to the obligatory released Stx EHEC are classified also among the Shigatoxin producing E. coli (STEC). EHEC are capable of causing a Hemorrhagic Colitis and some sequelae of dise ases such as the haemolytic uraemic syndrome. Due to their virulence factor s they can be divided into typical and non-typical EHEC. Typical EHEC posse ss a pathogenicity island (Locus of Enterocyte Effacement) harboring genes, which apart from the characteristic necrotic activity of Stx enable the pa thogens to closely attach to the epithelial cells of the intestinal mucosa and to destruct the microvilli. Additionally a so-called virulence plasmid codes for the production of a haemolysin, a peroxidase-katalase, an enterot oxin as well as a serine protease. EHEC are one of the world-wide most important causes of foodborne infection s. Depending upon the country, most of the incidences in 1998 varied betwee n 1 to 3 cases per 100 000 inhabitants. Since EHEC are only notifiable in a few countries, one must count however on substantially higher numbers. In Germany the estimated incidence is about 13 cases per 100 000 inhabitants. Since the first EHEC outbreaks were recognized in humans, studies investiga ting the prevalence of EHEC within animals were repeatedly performed. From the outset one assumed that cattle are a possible reservoir. Actually EHEC were isolated from fecal samples world-wide (typical and non-typical EHEC) from a large percentage of cattle (>50 %). Besides EHEC were isolated spora dically from fecal samples of other animals and healthy humans. The EHEC bacteria are shed by infected humans and animals, in particular by infected ruminants. They are spread over manure, slurry, sewage etc. Human s can get infected directly by contact with infected persons or animals or indirectly by contaminated food, water etc. The clinical outcome within humans appears as aqueous to bloody diarrhea. B eyond that approximately 5 to 10 % of the patients develop the haemolytic u raemic syndrome. In contrast to humans, animals are mostly infected clinica lly inapparent. The therapy is based upon a symptomatic treatment. At present in man the control of EHEC infections concentrates on a particul arly strict hand hygiene after the contact with infected humans and animals (above all ruminants). Since EHEC are heat sensitive, the prophylaxis by s ufficient heating of risk food (raw milk, ground beef) is of special import ance. In veterinary medicine above all EHEC infections must be controlled in rumi nants, which are the primary reservoir. Due to the wide spread of EHEC in t he ruminant population it is not realistic to demand an EHEC free cattle st ock. Since EHEC are spread only via fecal excretion, at present it is most: important to reduce the fecal shedding and to avoid fecal contamination of food of animal origin. In detail prophylactic hygienic measures concerning the farm management, the feeding hygiene, the food hygiene, the meat: hygi ene as well as the food hygiene are available.