Safeguarding public and animal health
Review of the major outbreak of E. coli O157 in Surrey, 2009
The report of the independent investigation into the large outbreak of E. coli O157 at Godstone Farm in Surrey has been published.
The investigation, commissioned by the Health Protection Agency, was led by Professor George Griffin, Professor of Infectious Diseases and Medicine at St. George's, University of London.
A multi-agency committee has been set up to consider how best to take forward the report's recommendation. The Committee is chaired by the HPA and membership includes representatives from Defra, Department of Health, the VLA, the NFU, Health and Safety Executive, Chartered Institute of Environmental Health, Local Government Regulation and the National Farm Attraction Network.
Q1: How was VLA involved in the Review of the major outbreak of E. coli O157 in Surrey, 2009?
The VLA has a long and successful history of working closely with the public health authorities in the investigation of VTEC O157 infection acquired from direct contact with animals.
This includes providing advice on animal-associated issues, on-farm animal sampling and undertaking microbiological cultures for E. coli O157 on animal samples at our specialist Regional Laboratories.
We played a major role in helping to establish the animal sources of the Godstone Farm outbreak and will collaborate with the HPA and other agencies in implementing the recommendations of the Griffin Report, including addressing relevant research needs.
Q2: What was the VLA's role in the outbreak investigation?
At the request of the Health Protection Agency, the VLA visited and took samples from Godstone Farm on 7, 16 and 24 September 2009.
The VLA has a long history of close working with the HPA and supporting it in protecting human health. Our veterinary experts help to identify how these infections were caused.
Q3: What samples were taken at Godstone Farm and what was found?
We found that 33 of 102 samples taken on 7/9/09 yielded verocytotoxin producing E. coli (VTEC) O157. The positive samples came from ewes, lambs, pigs, goats, cattle and ponies, and from floor-samples of pooled rabbit droppings. We did not find it in a water sample (pond water) or six samples of sandpit sand.
On 16 September, 17 environmental samples, 115 samples from ‘pet animals’ (rabbits, ducks, chickens, guinea pigs, ferrets, mice, chipmunks, turkeys, geese, quail and rhea) and droppings from wild rabbits were taken. None of the animal specimens yielded VTEC O157. Two of the 17 environmental samples, both from the floor of the main barn, yielded VTEC O157. Further sampling, including repeat sampling of pet rabbits, all proved negative.
Q4: Were the E. coli found in the animals at Godstone Farm the same as the ones causing the infection in children?
11 of these 33 E. coli isolates collected on 7 September representative of different animal species were examined in detail, and confirmed by the HPA to be indistinguishable from those causing infection in the human cases.
Q5: What is the difference between verotoxigenic E. coli and other E. coli?
Just as there are many different types of animal, e.g. breeds of dog, there are different types of E. coli. One type of these bacteria produces a toxin (poison) called verocytotoxin (verotoxin), which is sometimes referred to as shiga toxin. There are two types of this toxin; some strains produce one or other, and some produce both.
Q6: Are all verotoxin producing E. coli the same?
No. They can be further broken down, with one called O157 being the most common to produce the disease in humans in Great Britain.
Q7: How do the toxins cause disease?
They damage cells in the body, and are particularly damaging to cells of the kidney.
Q8: How do you catch VTEC O157?
By ingestion through either eating contaminated food, including meat and non-meat products, or hand-to-mouth following contact with infected material/animals, especially their droppings. Infection can also be spread person-to-person, particularly in closed settings.
Q9: Where do animals get it from?
They catch it from other animals or contaminated environment.
Q10: Does VTEC cause disease in animals?
Only some VTEC do. The O157 serogroup does not.
Q11: What can farms do to reduce the risk?
Guidance and advice are available from the VLA and the HSE. This primarily covers prevention of acquiring VTEC, prevention of spread if acquired and preventing establishment.
Q12: Does Defra/VLA ever screen animals for VTEC?
Yes, as part of surveys on cattle farms and at abattoirs. This has shown that a few animals harbour VTEC, particularly cattle and sheep. Infection is most common in calves. We also test animals in support of the HPA and local authorities when there is a suspect link between human cases and animals (see ‘Further E. coli info’ on the right).
Q13: Why don’t you routinely check?
Because VTEC O157 doesn’t cause illness in animals, it is not looked for by vets in animal disease investigations. Our surveys and other studies show that a small proportion of livestock and wild animals will be shedding these bacteria. This has led to the precautionary approach that management of public-animal exposures should assume a risk of exposure to VTEC from animals and appropriate hygiene precautions should be adopted routinely.
Q14: In other open farm investigations associated with human cases what animals and what proportion of animals were positive?
In 10 years of VLA experience of open farm investigations where human VTEC O157 illness has been possibly linked to animal contact, VTEC O157 has been confirmed in 19 (60%) of 31 farm investigations. On positive farms, the highest proportion of positive samples was in cattle (29%), followed by sheep (24%), donkeys (15%), pigs (14%), horses (12%) and goats (10%). It should however be remembered that these farms were sampled because of perceived links with human cases and not as part of a survey and results may not be representative of all open farms.
The HPA requested assistance from the VLA in the investigation of 14 VTEC O157 outbreaks (including the Godstone Farm outbreak) in 2009 that were possibly linked to animal contact. Details of the VLA investigations can be found in the VLA Non-Statutory Zoonoses Annual Report for 2009.
Reference
G.C. Pritchard et al (2009). Verocytotoxigenic Escherichia coli O157 in animals on public amenity premises in England and Wales, 1997 to 2007. Veterinary Record 164: 544-9