The incubation period of VTEC O157 generally ranges from 2 to 14 days, with a median of 3 to 4 days [1,2,4]. Some people have been shown to carry VTEC or VTEC O157 without developing symptoms.

Gastroenteritis

Some people infected with VTEC have typical gastroenteritis symptoms i.e. diarrhoea with or without vomiting, abdominal cramps and fever. Sometimes there is some blood mixed in with the diarrhoea.

Symptoms may last a few days and then disappear within a week or so. Management of cases is purely supportive. Antibiotics are NOT recommended and might exacerbate the sequelae of infection [5 ]. If you suspect a case, have a stool sample collected and send it to your local hospital laboratory where it will be tested for the presence of presumptive VTEC O157 and report the case to your local health protection unit (as it is mandatory to notify all cases of food poisoning). Screening (contacts of the patient) and exclusion (from school/work) may be necessary upon advice from the health protection unit. If the sample is positive, a culture from it should be sent by the hospital to the Department of Gastrointestinal, Emerging and Zoonotic Infections (GEZI) at the HPA Centre for Infections, where it will be examined in more detail.

Haemorrhagic colitis

The toxins released by VTEC strains and their ability to adhere to and damage the intestinal epithelium can cause patients to develop an inflamed colon which bleeds a lot, resulting in very bloody diarrhoea and severe abdominal pain. Often there is no fever with haemorrhagic colitis. Symptoms can be severe and may last for several days. Symptoms typically clear completely within two weeks.

Haemolytic uraemic syndrome (HUS)

It is thought that up to 2-7% of cases infected with VTEC develop HUS after an initial period (a prodrome) of gastroenteritis or haemorrhagic colitis. The receptors for Vero cytotoxins are present on epithelial cells, particularly in kidney tissue and in the central nervous system. The toxins damage endothelial cells generating thrombin and fibrin deposits in the microvasculature. This goes on to cause leakage and tissue oedema. Erythrocytes are damaged as they pass through small vessels partially occluded by thrombus and haemolysis subsequently occurs. Fewer than 5% of childhood HUS cases die [3 ].

Thrombotic thrombocytopaenic purpura (TTP)

Some people (mainly adults) infected with VTEC develop TTP. This may present as flu-like symptoms (prodrome) including fever, fatigue and generalised malaise and arthralgias. Then a patient may present with some or all of the classic symptoms including: thrombocytopaenia (with petechial haemorrhages in the lower extremities and a tendency to bleed), other haematological changes (anaemia), fever, renal changes (gross haematuria, microscopi haematuria, raised urea and creatinine) and neurological deficits.

Public health, control and epidemiology

Although the principle reservoir for VTEC O157 in the UK is cattle, therefore making the disease a zoonosis, secondary infections are also acquired, by person-to-person spread by direct contact (faecal-oral). This is particularly important in households, nurseries, primary schools and residential care institutions. Therefore, efforts are undertaken by public health professionals to control the source of infection. The disease is also under surveillance to increase our understanding of the epidemiology of VTEC in England.

 

References

1. Control of Communicable Diseases Manual. Washington: American Public Health Association, 2004.
2. Kohli HS, Chaudhuri AKR, Todd WTA, Mitchell AAB, and Liddell KG. A severe outbreak of E. coli O157 in two psychogeriatric wards. J Public Health 1994; 16:11-5.
3. Lynn R, O'Brien S, Taylor CM, Adak BA, Chart H, Cheasty T, Coia JE, Gillespie IA, Locking ME, Reilly WJ, Smith HR, Waters A, Willshaw GA. Childhood Hemolytic Uremic Syndrome, United Kingdom and Ireland. Emerging Infectious Diseases 2005; 11:590-6.
4. Marsh J, MacLeod AF, Hanson MF, Emmanuel FXS, Frost JA, and Thomas A. A restaurant-associated outbreak of E. coli O157 infection. J Public Health 1992; 14:78-83.
5. Wong CS, Jelacic S, Habeeb RL, Watkins SL, and Tarr PI. The Risk of the Hemolytic-Uremic Syndrome after Antibiotic Treatment of Escherichia coli O157:H7 Infections. N Engl J Med 2000; 342:1930-6.

 

Last modified: 29 July 2009