The bacteria are transmitted chiefly by eating the following foods: raw minced beef, minced pork sausage, salami, unpasteurised milk, unpasteurised apple juice, but also vegetarian foods that have been cultivated on fields fertilised with cattle slurry and eaten raw (e.g. green-leaf vegetables, sprouts, spinach).
Moreover, transmission following contact with ruminants (pet zoos) can also play an important role, if hands are not washed appropriately (washing with soap) afterwards; or the human-to-human infection chain, predominantly observed in community institutions (nurseries, retirement homes, etc.). The number of pathogens required for an infection is very low at about 100 bacteria.
The incubation period is 1-3 days, in rare cases up to 8 days.
The infection starts with watery diarrhoea, which may contain blood after a few days and which may be accompanied by severe nausea, vomiting and abdominal pains. The disease is usually self-limited and continues for eight to 10 days on average.
About 10 % to 20 % of the patients will develop haemorrhagic colitis with bloody stools and, to some extent, fever.
In 5 % to 10 % of the patients, predominately infants, a typical secondary disease – haemolytic-uraemic syndrome (HUS) – could develop a few days after the diarrhoea has begun. In this case, the Shiga toxins bind to specific receptors in the cell membranes (mainly in the kidney endothelium), damaging them. They destroy the tiny blood capillaries, which can subsequently lead to kidney failure (no urine production), anaemia, reduced number of platelets (thrombocytes), skin erythrodiapedesis and neurological changes.
Diarrhoea and one of the following conditions:
- Children below the age of 6
- Visible blood in stools
- Haemorrhagic colitis
- Patients’ contact persons suffering from HUS
- Paediatric patients with acute kidney failure
- Patients working directly in the production, processing, treatment or market placement of foods; or working in kitchen, restaurant or other community facilities.
ELISA or PCR (toxin or toxin gene detection) screening is carried out on enriched stool specimens, when there is the clinical suspicion of this disease. In the case of a positive screening result, pathogen cultures are grown for diagnosis. In the case of HUS, diagnosis using the detection of specific antibodies in the blood could be attempted if the pathogen identification in the stool sample has yielded a negative result.
Suspicion or cases of VTEC infections must be reported to the authorities!
Treatment to restore the body’s water and electrolyte balance is sufficient. Treatment with antibiotics, on the other hand, is considered contraindicated in general, as the bacteria produce more toxins under the influence of antibiotics -- thus, increasing the level of complications. Serious secondary diseases (e.g. HUS) require intensive medical treatment. There were 130 VTEC infections reported in 2013. In 17 of the 130 cases, the haemolytic-uraemic syndrome (HUS) occurred as a severe complication.
Strict adherence to hygiene regulations in the production, processing, storing, transportation and sale of animal-based foods, such as the washing of hands after contact with animals and before eating, is vital as agricultural animals are the primary reservoir for the bacteria.
Raw animal-based foods and other easily perishable foods (e.g. milk and dairy products, meat, cold meats and hams, deli salads) should always be stored at refrigerator temperature. Additionally, meat should not be prepared at the same time as foods that are for direct consumption (e.g. salads) to avoid cross contamination. In any case, avoid using the same equipment and surfaces for preparing different kinds of foods.
Unpasteurised milk should not be consumed, only after being treated with heat.
Individuals suffering from a VTEC infection must not work in commercial food production, processing or sales until the risk of spreading the disease has ceased and they have been cleared by the health authorities. This also applies for staff members in restaurant kitchens, cafeterias, hospitals, infant and children’s homes, as well as in community catering.
A total of 375 meat samples (333 fresh meat samples, 23 fresh game meat samples, 19 ready-to-eat meat samples) were tested for VTEC in 2013. VTEC was found in three of these samples (twice in raw game meat, once in fresh meat from an undisclosed animal species). Three of 221 fermented sausages that were examined contained VTEC. No VTEC was detected in the 95 cheese samples (from unpasteurised and pasteurised milk), six milk samples and 79 other food samples (fruit, vegetables, other ready food).
None of VTEC isolated were of a serotype that causes infections in humans on a regular basis and none of them carried the intimen gene, an important virulence factor that triggers diseases in humans.