BBC Scotland's rural affairs correspondent Ken Rundle explains the background to claims that people living, working or enjoying the countryside could face an increased risk of E.coli O157 infection.
There are many types of Escherichia Coli bacteria, many of which humans can live with unharmed. The lethal strain, E.coli O157, has only been identified relatively recently.
E.coli O157 was first noticed in 1982 after a fatal food poisoning outbreak in America caused by undercooked burgers. Since then it has been found around the world, and linked not just to meat but also to salad crops and to countryside activities in general.
For reasons yet unknown, Scotland has a particularly high incidence of E.coli O157.
This bacteria is described as a "VTEC". It produces potent “vero cytoxins” and as few as ten of the bugs can cause humans severe infectious gastroenteritis. The old, weak and very young are particularly vulnerable and can suffer kidney failure, with the infection often fatal.
Contamination of surfaces
E.coli O157 is carried in the last few inches of the intestines of cattle and sheep and causes no harm to the animals. It is killed by cooking, washing, disinfection and sterilisation procedures such as pasteurisation and irradiation.
Risks are increased if infected dung contaminates surfaces. Grass fields, food crops fertilized by farmyard manure, troughs, farm buildings and brushes smeared with dung can all carry infection, as can other animals. Contamination on animal hides can be transferred on to raw meat during the slaughtering process. This in turn can lead to cross-contamination of food in a domestic or commercial fridge.
In Lanarkshire during 1996, 21 elderly people died from eating meat pies distributed by a Butcher's shop in Wishaw. The separation between raw and cooked meat in the premises was found to have been poor.
A subsequent enquiry under the chairmanship of Professor Hugh Pennington led to major changes in food law and food processing methods. Many of these were specific to Scotland, although others were adopted industry-wide. The revised hygiene laws are policed by the Food Standards Agency (FSA).
The key measures mostly involve the production and handling of meat. Strict rules aim to cut out opportunities for cross-contamination. Retailers and caterers must separate cooked and raw meats and keep raw meat apart from vegetable preparation areas. Farmers must ensure only clean animals go to the abattoirs, and inside those plants other measures have been put in place to keep meat clean.
Movement of animals
It is difficult to identify which animals might shed E.coli O157. There appears to be a link between cattle either being taken inside for the winter or being allowed outside in the spring. However, any shedding of the bacteria might not last long.
At present there is no easy test or drug therapy to help avoid the risk, although some ways of reducing shedding of the bacteria are being tested.
Since the 1996 Wishaw outbreak there have been several others. Recent cases have involved domestic water supplies, salads (organic as well as conventional) and even nurseries where the bacteria has been passed from child to child during nappy changing. Professor Pennington is about to begin another enquiry following another serious case affecting children in Wales.
Landowners planning to use their property for camping or public events must clear the land of grazing animals enough time in advance of the event for the risk of infection to be reduced.
This still poses a problem for those accessing land in an informal basis, for example wild camping or having a picnic. The advice is to wash hands carefully before eating, and to avoid taking young children to areas recently occupied by animals.
Nancy Nicolson will discuss the findings of the conference on BBC Radio Scotland Grassroots on Saturday 3 November.
Page first published on Tuesday 30th October 2007
Page last updated on Tuesday 17th June 2008