A quantitative risk assessment for the safety of carcase storage systems for scrapie infected farms.

AIMS: To determine the risk associated with the use of carcase storage vessels on a scrapie infected farm. METHODS AND RESULTS: A stochastic quantitative risk assessment was developed to determine the rate of accumulation and fate of scrapie in a novel low-input storage system. For an example farm infected with classical scrapie, a mean of 10(3·6) Ovine Oral ID50 s was estimated to accumulate annually. Research indicates that the degradation of any prions present may range from insignificant to a magnitude of one or two logs over several months of storage. CONCLUSIONS: For infected farms, the likely partitioning of remaining prion into the sludge phase would necessitate the safe operation and removal of resulting materials from these systems. If complete mixing could be assumed, on average, the concentrations of infectivity are estimated to be slightly lower than that measured in placenta from infected sheep at lambing. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first quantitative assessment of the scrapie risk associated with fallen stock on farm and provides guidance to policy makers on the safety of one type of storage system and the relative risk when compared to other materials present on an infected farm.

The greenhouse emissions footprint of free-range eggs.

Eggs are an increasingly significant source of protein for human consumption, and the global poultry industry is the single fastest-growing livestock sector. In the context of international concern for food security and feeding an increasingly affluent human population, the contribution to global greenhouse-gas (GHG) emissions from animal protein production is of critical interest. We calculated the GHG emissions footprint for the fastest-growing sector of the UK egg market: free-range production in small commercial units on mixed farms. Emissions are calculated to current Intergovernmental Panel on Climate Change and UK standards (PAS2050): including direct, indirect, and embodied emissions from cradle to farm gate compatible with a full product life-cycle assessment. We present a methodology for the allocation of emissions between ruminant and poultry enterprises on mixed farms. Greenhouse gas emissions averaged a global warming potential of 2.2 kg of CO2e/dozen eggs, or 1.6 kg of CO2equivalent (e)/kg (assuming average egg weight of 60 g). One kilogram of protein from free-range eggs produces 0.2 kg of CO2e, lower than the emissions from white or red meat (based on both kg of meat and kg of protein). Of these emissions, 63% represent embodied carbon in poultry feed. A detailed GHG emissions footprint represents a baseline for comparison with other egg production systems and sources of protein for human consumption. Eggs represent a relatively low-carbon supply of animal protein, but their production is heavily dependent on cereals and soy, with associated high emissions from industrial nitrogen production, land-use change, and transport. Alternative sources of digestible protein for poultry diets are available, may be produced from waste processing, and would be an effective tool for reducing the industry's GHG emissions and dependence on imported raw materials.

Subclinical infection and asymptomatic carriage of gastrointestinal zoonoses: occupational exposure, environmental pathways, and the anonymous spread of disease.

Asymptomatic carriage of gastrointestinal zoonoses is more common in people whose profession involves them working directly with domesticated animals. Subclinical infections (defined as an infection in which symptoms are either asymptomatic or sufficiently mild to escape diagnosis) are important within a community as unknowing (asymptomatic) carriers of pathogens do not change their behaviour to prevent the spread of disease; therefore the public health significance of asymptomatic human excretion of zoonoses should not be underestimated. However, optimal strategies for managing diseases where asymptomatic carriage instigates further infection remain unresolved, and the impact on disease management is unclear. In this review we consider the environmental pathways associated with prolonged antigenic exposure and critically assess the significance of asymptomatic carriage in disease outbreaks. Although screening high-risk groups for occupationally acquired diseases would be logistically problematical, there may be an economic case for identifying and treating asymptomatic carriage if the costs of screening and treatment are less than the costs of identifying and treating those individuals infected by asymptomatic hosts.

Seroprevalence and risk factors associated with Escherichia coli O157 in a farming population.

Evidence suggests that frequent and direct exposure to domestic animals has made farmers less susceptible to symptomatic Escherichia coli O157 infection than other members of the community. We have quantified the seroprevalence of antibodies to E. coli O157 lipopolysaccharide (LPS) from a representative cohort of farm workers in three geographically distinct regions of the United Kingdom during two sampling rounds over a 2-year period. All participants completed a questionnaire to determine the range and extent of recent animal contact alongside other potential occupational and environmental exposure routes. A total of 31/946 (3.3%) serum samples contained antibodies to E. coli O157 LPS (from both rounds combined). On the second sampling round, a significant difference in seropositivity was apparent between the three regions, with enhanced seroprevalence linked to recent contact with beef cattle, having a private water supply and contact with a child under 5 years old. Only five seropositive people reported symptoms of a gastrointestinal tract infection, although these symptoms were mild. These results further support the premise of acquired immunity to E. coli O157 associated with prolonged antigenic exposures within the farming environment.

Eliciting expert opinion on the effectiveness and practicality of interventions in the farm and rural environment to reduce human exposure to Escherichia coli O157.

Few hard data are available on emergent diseases. However, the need to mitigate and manage emergent diseases has prompted the use of various expert consultation and opinion elicitation methods. We adapted best-worst scaling (BWS) to elicit experts' assessment of the relative practicality and effectiveness of measures to reduce human exposure to E. coli O157. Cattle vaccination was considered the most effective and hand-washing was considered the most practical measure. BWS proved a powerful tool for expert elicitation as it breaks down a cognitively burdensome process into simple, repeated, tasks. In addition, statistical analysis of the resulting data provides a scaled set of scores for the measures, rather than just a ranking. The use of two criteria (practicality and effectiveness) within the BWS process allows the identification of subsets of measures judged as potentially performing well on both criteria, and conversely those judged to be neither effective nor practical.

Differences in the perceptions of farmers and veterinary surgeons about the efficacy of mitigation strategies for controlling bluetongue.

This study used adaptive conjoint analysis to quantify veterinary surgeons' and farmers' perceptions of a number of previously identified, viable mitigation strategies for controlling bluetongue. Data were collected using a questionnaire survey and face-to-face interviews. A total of 178 completed questionnaires were collected, 121 from farmers and 57 from veterinary surgeons. There were strong significant differences between the strength of preference of farmers and veterinary surgeons for a number of strategies. There was also large variation in the strength of preference among veterinary surgeons with respect to options involving vaccination. The results suggest uncertainty among both veterinary surgeons and farmers regarding the efficacy of current strategies, and suggest the need for dissemination of information to veterinary surgeons and farmers to be better coordinated.

Plant metabolites and nutritional quality of vegetables.

Vegetables are an important part of the human diet and a major source of biologically active substances such as vitamins, dietary fiber, antioxidants, and cholesterol-lowering compounds. Despite a large amount of information on this topic, the nutritional quality of vegetables has not been defined. Historically, the value of many plant nutrients and health-promoting compounds was discovered by trial and error. By the turn of the century, the application of chromatography, mass spectrometry, infrared spectrometry, and nuclear magnetic resonance allowed quantitative and qualitative measurements of a large number of plant metabolites. Approximately 50000 metabolites have been elucidated in plants, and it is predicted that the final number will exceed 200000. Most of them have unknown function. Metabolites such as carbohydrates, organic and amino acids, vitamins, hormones, flavonoids, phenolics, and glucosinolates are essential for plant growth, development, stress adaptation, and defense. Besides the importance for the plant itself, such metabolites determine the nutritional quality of food, color, taste, smell, antioxidative, anticarcinogenic, antihypertension, anti-inflammatory, antimicrobial, immunostimulating, and cholesterol-lowering properties. This review is focused on major plant metabolites that characterize the nutritional quality of vegetables, and methods of their analysis.

A generic spreadsheet model of a disease epidemic with application to the first 100 days of the 2001 outbreak of foot-and-mouth disease in the UK.

A generic, stochastic spreadsheet model was developed to calculate the number of cases within the first 100 days of a propagating epidemic and with the ability to incorporate generic control measures. Foot-and-mouth disease (FMD) epidemics were simulated with a range of assumptions about the number of cases incubating the disease on day 1 and the efficiency of control measures. Particularly severe epidemics resulted from scenarios with low efficiency of control measures and high numbers incubating. Control measures that prevented 0.8 of cases from resulting in new cases were able to reduce substantially the cumulative number of cases. The results of various scenarios using the model were compared to the number of cases of FMD in the first 100 days of the 2001 outbreak in the UK, with specific reference to cases in Cumbria and Anglesey. Potential practical and educational applications of the model are discussed.

Honeybee, Apis mellifera (Hymenoptera: Apidae), leaf damage on Alnus species in Uganda: a blessing or curse in agroforestry?

It is a dictum that Apis mellifera Linnaeus is innocuous in agricultural ecosystems. This study provides the first record of A. mellifera as a significant defoliator of Alnus species. Careful field observations coupled with microscopic examination provided convincing evidence implicating A. mellifera as the cause of leaf perforation on Alnus species in Uganda. Apis mellifera was observed foraging selectively on young Alnus leaves and buds in search of a sticky substance, apparently propolis. In so doing, the bee created wounds that enlarged and caused tattering of Alnus leaves as they matured. Biological surveys indicated that the damage was prevalent and occurred widely, particularly on Alnus acuminata Kunth in Uganda. Incidence of the Apis mellifera damage on Alnus acuminata peaked in the dry season, with up to 90% of leaves emerging per shoot per month damaged, and was lowest in the wet months during peak leaf emergence. Apis mellifera leaf damage was consistently higher on Alnus acuminata than A. nepalensis D. Don., on saplings than mature trees, and on sun exposed than shaded leaves. The activity of honeybees may be detrimental to the productivity of Alnus, yet the substance for which the insect forages on Alnus is a resource with potential economic importance.