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Panic pending over farming waste
Cross-talk
Panic pending over farming waste I venture a prediction—one that I fear will, but hope will not, prove to be accurate. This year, next year, or some time, there will be a serious outbreak of food poisoning and haemolytic uraemic syndrome caused by Escherichia coli O157:H7 traced to the spreading of farming waste over arable land. Several of the victims will develop acute renal failure, and there may be fatalities. The incident will occur somewhere in Europe or the USA, provoking a national outcry. The government will be bounced into drafting legislation to prohibit the practice that led to the outbreak. One of the characteristics of modern government is the introduction of new measures and even laws in instant, panicky responses to happenings that arouse great public concern. In every case the problem has been apparent, but ignored, for several years. A madman, shooting children in Dunblane, Scotland, triggered the hasty enactment of illconsidered legislation on the ownership of hand-guns. More recently, a costly initiative was announced to improve school meals throughout Britain simply because a celebrity chef made a fuss. My E coli scenario is not implausible. Indeed, the danger is in several ways more extensive than I have described. Farmers in many countries around the world routinely fertilise their land with sewage and with effluents from abattoirs, food industries, and animal husbandry. The only one of these materials banned in Europe and the USA is untreated sewage. So slaughterhouse waste and slurries from cowsheds and piggeries, for example, are disseminated on both arable and grassland. As I pointed out last year (Lancet Infect Dis 2004; 4: 650), such “natural” fertilisers may well carry pathogens.
These concerns persuaded Lisa Avery and her colleagues at the universities of Aberdeen and of Wales, Bangor, UK, to assess the scale of the problem (J Appl Microbiol 2005; 98: 814–22). They did so by monitoring the persistence of E coli O157:H7 in several types of waste widely used by farmers, in an attempt to assess the potential risks associated with the practice. Most documented cases of food poisoning by this organism have followed the consumption of undercooked beef products. However, outbreaks have also been traced to contaminated vegetables, while there is substantial circumstantial evidence for the role of animal wastes in causing infections—eg, in campers. Avery and her co-workers hoped to quantify the hazard by evaluating the survival of E coli O157:H7 over 2 months in various types of waste commonly applied to agricultural land. The 27 materials that they studied included five abattoir effluents, five cattle slurries, and four commercial creamery wastes, as well as samples of both treated and untreated sewage. All were inoculated with the test organism and then incubated at 10oC. Although counts gradually declined during the incubation period, the E coli strain was still viable 2 months later in 77% of the wastes. These included most of the cattle slurries and abattoir effluents and all of the creamery wastes. “Our results indicate that current legislation may be insufficient to protect the environment from E coli O157:H7 contamination from untreated wastes spread to land”, the researchers conclude. “While it is dangerous to extrapolate our data to try to predict E coli O157 survival after land application, higher pathogen numbers remaining in waste at the time of application would pose an increased risk of the organism surviving in sufficient numbers to cause infection. Thus the long-term survival of E coli O157 in these wastes has implications for the subsequent transmission to crops and adjacent watercourses and also to direct infection of humans and animals in contact with the contaminated land.” Fortunately, this study also highlights a possible strategy to reduce such risks. Since E coli O157 counts declined during incubation, simple storage would probably help to reduce the pathogen load. However, this would be unlikely to eliminate the hazard entirely, and certainly could not be relied upon to do so. We have a problem, as yet unsolved.
Bernard Dixon 130 Cornwall Road, Ruislip Manor, Middlesex HA4 6AW, UK; [email protected]
http://infection.thelancet.com Vol 5 July 2005
397
Panic pending over farming waste I venture a prediction—one that I fear will, but hope will not, prove to be accurate. This year, next year, or some time, there will be a serious outbreak of food poisoning and haemolytic uraemic syndrome caused by Escherichia coli O157:H7 traced to the spreading of farming waste over arable land. Several of the victims will develop acute renal failure, and there may be fatalities. The incident will occur somewhere in Europe or the USA, provoking a national outcry. The government will be bounced into drafting legislation to prohibit the practice that led to the outbreak. One of the characteristics of modern government is the introduction of new measures and even laws in instant, panicky responses to happenings that arouse great public concern. In every case the problem has been apparent, but ignored, for several years. A madman, shooting children in Dunblane, Scotland, triggered the hasty enactment of illconsidered legislation on the ownership of hand-guns. More recently, a costly initiative was announced to improve school meals throughout Britain simply because a celebrity chef made a fuss. My E coli scenario is not implausible. Indeed, the danger is in several ways more extensive than I have described. Farmers in many countries around the world routinely fertilise their land with sewage and with effluents from abattoirs, food industries, and animal husbandry. The only one of these materials banned in Europe and the USA is untreated sewage. So slaughterhouse waste and slurries from cowsheds and piggeries, for example, are disseminated on both arable and grassland. As I pointed out last year (Lancet Infect Dis 2004; 4: 650), such “natural” fertilisers may well carry pathogens.
These concerns persuaded Lisa Avery and her colleagues at the universities of Aberdeen and of Wales, Bangor, UK, to assess the scale of the problem (J Appl Microbiol 2005; 98: 814–22). They did so by monitoring the persistence of E coli O157:H7 in several types of waste widely used by farmers, in an attempt to assess the potential risks associated with the practice. Most documented cases of food poisoning by this organism have followed the consumption of undercooked beef products. However, outbreaks have also been traced to contaminated vegetables, while there is substantial circumstantial evidence for the role of animal wastes in causing infections—eg, in campers. Avery and her co-workers hoped to quantify the hazard by evaluating the survival of E coli O157:H7 over 2 months in various types of waste commonly applied to agricultural land. The 27 materials that they studied included five abattoir effluents, five cattle slurries, and four commercial creamery wastes, as well as samples of both treated and untreated sewage. All were inoculated with the test organism and then incubated at 10oC. Although counts gradually declined during the incubation period, the E coli strain was still viable 2 months later in 77% of the wastes. These included most of the cattle slurries and abattoir effluents and all of the creamery wastes. “Our results indicate that current legislation may be insufficient to protect the environment from E coli O157:H7 contamination from untreated wastes spread to land”, the researchers conclude. “While it is dangerous to extrapolate our data to try to predict E coli O157 survival after land application, higher pathogen numbers remaining in waste at the time of application would pose an increased risk of the organism surviving in sufficient numbers to cause infection. Thus the long-term survival of E coli O157 in these wastes has implications for the subsequent transmission to crops and adjacent watercourses and also to direct infection of humans and animals in contact with the contaminated land.” Fortunately, this study also highlights a possible strategy to reduce such risks. Since E coli O157 counts declined during incubation, simple storage would probably help to reduce the pathogen load. However, this would be unlikely to eliminate the hazard entirely, and certainly could not be relied upon to do so. We have a problem, as yet unsolved.
Bernard Dixon 130 Cornwall Road, Ruislip Manor, Middlesex HA4 6AW, UK; [email protected]
http://infection.thelancet.com Vol 5 July 2005
397