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| Report on the circumstances leading to the 1996 outbreak of infection with E.coli 0157 in Central Scotland, the implications for food safety and the lessons to be learned. |
| Chapter 5 Farms and E.coli O157 in Livestock |
| 5.1 When considering the circumstances of the outbreaks we examined and, in particular, the scope for preventive measures, we looked first at the potential primary sources of the organism and infection. Since it is generally accepted that the main reservoir of E.coli O157 exists in cattle, and possibly sheep, farms and livestock constitute the first critical points in the food production process. They also represent potential sources of direct and secondary infection with the organism. |
| Existing Knowledge and the Need for Further Research |
| 5.2 The issues surrounding the incidence and prevalence of the organism in farms and livestock, possible causes and the implications are extremely complex. While a lot of work has been done or is underway, there are still substantial gaps in knowledge - including, for example, about the effects of particular aspects of animal husbandry, the distribution of infection within the farm environment and sources of spread of infection. There are no treatments currently available to eradicate animal infection with the organism or to immunise against it. The reasons for animals becoming infected, and the extent and duration of excretion of E.coli O157, are not yet understood. |
| 5.3 There is, therefore, scope for further investigation and research into E.coli O157 on farms and in livestock. In our interim report, we made recommendations on (and the Secretary of State accepted) the need for research into the incidence and prevalence of the organism in cattle and other animals in Scotland. We were also made aware, during the course of our further work, of other on-going or proposed research in this area. |
| 5.4 The broader question of research is discussed further in Chapter 11. We were aware of the current extensive programme of research already being undertaken and we expect that further work on the prevalence, causes, treatment and prevention of E.coli O157 (and other VTECs) on farms and in livestock will be proposed. Given the number of issues we felt needed to be addressed, and the time and expertise needed to consider research proposals in any detail, we did not think that was an issue we should go into in great detail. We took the view that additional research in this area should generally be considered through normal Government processes and peer review and prioritised according to its merits - but with appropriate weight given to the apparently growing threat which the organism presents to public health. We believe, however, that the ultimate aim should be to reduce the prevalence of the organism in livestock, which should very substantially reduce the likelihood of subsequent human infection. |
| 5.5 Action to reduce the burden of infection on farms and in livestock should not, however, await the outcome of further research, which may take many years. Action can and should be taken now. That should include, specifically, measures to raise awareness amongst farm workers of the organism and its pathogenicity, the potential for infection and the measures which they can take to help prevent its occurrence either within the food chain or from direct or secondary infection from the farm environment. |
| Raising Awareness Amongst Farm Workers of the Organism and its Implications |
| 5.6 There is no doubt that recent outbreaks of infection have raised public awareness of E.coli O157 - particularly in Scotland. The focus of public and media attention has, however, tended to be on the management and local source of the outbreak. The presumption has most often been that the problem has resulted from the cross-contamination of food, most likely caused by a breakdown in hygiene standards at whichever premises provided food for the location or event implicated in the outbreak. |
| 5.7 The question of hygiene practices in food premises is considered in Chapter 7. Focusing entirely on these premises, however, fails to recognise the nature of the organism and the need to take measures to minimise contamination at all stages throughout the food production process. |
| 5.8 From a purely farming perspective, there is a risk that the issues raised by E.coli O157 could be regarded as irrelevant, or simply too difficult. Apart from anything else, it is not possible easily or with any certainty to identify animal infection with the organism. Since infection causes no illness in animals, there are no financial or animal husbandry incentives for farmers to seek it out. Even where infection may exist/have existed, there are currently no treatments available to eradicate it or prevent its spread. Despite the efforts that have been made to raise awareness, we are concerned that the net effect is that farmers may not be fully aware of the possibility of infection in their animals and therefore may lack awareness of the consequent potential for human infection. |
| Recognising and Minimising the Potential for Human Infection |
5.9 There is
good evidence of the spread of infection from animals
carrying the organism, so that there is at least the
potential for:-
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| 5.10 Available evidence suggests the most significant source of the spread of infection is animal faeces from infected livestock. For reasons which are not understood, infected livestock intermittently excrete E.coli O157 and it has been found to survive for extended periods in cattle excreta. Research suggests that, in cattle, it is calves that most frequently excrete the organism, followed by non-lactating cows then lactating cows. Again, the reasons for this are not known, although it may be that some form of resistance to the organism increases with the age of the animal. |
| 5.11 There is a need to ensure the appropriate recognition of risks of infection from livestock and the farm environment. Although there are relatively few cases reported from farm workers, farms remain a potential source of direct contamination. As we would not wish to see lost the educational and other benefits of, for example, school visits to farms we stress the need to ensure that appropriate, precautionary, hygiene measures are taken. We welcome the steps that have been taken by Government departments and others to raise the awareness of these issues and would wish to see them repeated and reinforced periodically. We also see a need for guidance to farm workers on 2 particular issues - the disposal of faecal waste/the use of slurry; and the need to present animals for slaughter in an appropriate, clean condition. We were aware of, and welcome, the steps taken by the National Farmers' Union of Scotland on the latter: we suggest the message needs to be regularly re-iterated and reinforced. |
| Farm Disposal of Faecal Waste/The Use of Slurry |
| 5.12 Although there is evidence of water, crop and vegetable contamination from E.coli O157, the impact of the spreading of slurry and manure on the land has not been fully evaluated. The available evidence is sparse and conflicting. Nonetheless, there seems to us to be a case for precautionary measures associated with that practice. |
| 5.13 The present evidence is not sufficiently strong to suggest that the spreading of slurry or manure should be prohibited. However, at the very least there would be benefits in educating farm workers about the potential hazards involved in the use of untreated slurry or manure - notably where material is to be spread in the vicinity of crops, fruit or vegetables (including in particular those which might be eaten raw) and near sources of private and potentially untreated water supplies. Local authorities, health boards and water authorities also need to be alive to the possibility and to consider the implications. Again, we are aware of guidance that has been issued in the past on these issues (most recently, last month in a circular to local authorities) and that further work is planned or underway. The value of treatments to decontaminate slurry before or during application to the land would seem to be worth further investigation. |
| The Presentation of Animals for Slaughter |
| 5.14 There is strong evidence that carcasses can and do become contaminated with E.coli O157 from contact with animal faecal material. This usually occurs either from dirty hides or the leakage of faecal material from animal intestines during their removal at slaughter. The following chapter looks at hygiene and processes in abattoirs and makes recommendations designed to help reduce the risks involved in that. There are, however, measures which farmers must take to help produce clean animals and hence safer meat. |
| 5.15 There is anecdotal evidence that animals may be well or richly fed prior to presentation for slaughter - to increase live weight and hence the price paid to the farmer. Apart from increasing the amount of faeces likely to be produced by the animal (which will increase the potential for cross-contamination during transport or holding), this may increase the possibility of the animal's intestines bursting during removal at slaughter, with consequent increased risk of carcase contamination. We have been assured that this is not a widespread problem. Nevertheless, farmers need to be educated about the contamination risks which over-feeding may bring to the slaughter process. It has also been suggested that there may be benefits in managing animals' diets, immediately prior to slaughter. Again, these issues may be worth further exploration. |
| 5.16 It is vital that farmers are made fully aware of their responsibility to send animals to slaughter in a clean condition. This obligation lies with them and not slaughterhouses or the inspection services. Animals which have been clipped in the abdominal and hindquarters area, for example, are generally presented for slaughter in a cleaner condition. We suggested in our interim report that the Meat Hygiene Service (MHS) should consider and issue a clear definition of "dirty" for the guidance of those involved, particularly the Official Veterinary Surgeon (OVS). We warmly welcome the work which has been done by the MHS since production of our interim report in establishing a more objective scoring system to differentiate between clean and dirty animals and the announcement, on 20 March 1997, of its Clean Livestock Strategy. That must be used as part of the education process to help ensure that farmers understand and achieve the required standards. The need for clipping and washing if necessary, and for clean and dry bedding for animals in transportation and holding, should be emphasised. This must be backed up by rigorous enforcement by the MHS at abattoirs. |
| Recommendations |
| 5.17
In summary we recommend: 1. that there should be an education/awareness programme for farm workers, repeated and updated periodically as appropriate, to ensure they are aware: a. of the existence, potential prevalence and nature of E.coli O157; b. of the potential for the spread of infection on farms in a number of ways, including notably from faecal material, and of the consequent need for scrupulous personal hygiene; c. of the need for care in the use of untreated slurry or manure; and d. of the absolute requirement for the presentation of animals in an appropriate, clean condition for slaughter; and |
| 2. That all of this must be backed up by rigorous enforcement by the MHS at abattoirs. |
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