Spatial multi-criteria decision analysis to predict suitability for African swine fever endemicity in Africa

Background African swine fever (ASF) is endemic in several countries of Africa and may pose a risk to all pig producing areas on the continent. Official ASF reporting is often rare and there remains limited awareness of the continent-wide distribution of the disease. In the absence of accurate ASF outbreak data and few quantitative studies on the epidemiology of the disease in Africa, we used spatial multi-criteria decision analysis (MCDA) to derive predictions of the continental distribution of suitability for ASF persistence in domestic pig populations as part of sylvatic or domestic transmission cycles. In order to incorporate the uncertainty in the relative importance of different criteria in defining suitability, we modelled decisions within the MCDA framework using a stochastic approach. The predictive performance of suitability estimates was assessed via a partial ROC analysis using ASF outbreak data reported to the OIE since 2005. Results Outputs from the spatial MCDA indicate that large areas of sub-Saharan Africa may be suitable for ASF persistence as part of either domestic or sylvatic transmission cycles. Areas with high suitability for pig to pig transmission (‘domestic cycles’) were estimated to occur throughout sub-Saharan Africa, whilst areas with high suitability for introduction from wildlife reservoirs (‘sylvatic cycles’) were found predominantly in East, Central and Southern Africa. Based on average AUC ratios from the partial ROC analysis, the predictive ability of suitability estimates for domestic cycles alone was considerably higher than suitability estimates for sylvatic cycles alone, or domestic and sylvatic cycles in combination. Conclusions This study provides the first standardised estimates of the distribution of suitability for ASF transmission associated with domestic and sylvatic cycles in Africa. We provide further evidence for the utility of knowledge-driven risk mapping in animal health, particularly in data-sparse environments.</p

Evaluation of Methods for Diagnosing Contamination in Rural Wells

Three diagnostic procedures were tested to determine their potential usefulness in identifying faulty rural wells: (1) monitoring wells were constructed at three depths near each of three rural wells having a history of nitratenitrogen and/or herbicide contamination, and all wells were sampled daily for four weeks and tested for nitrate-nitrogen, atrazine, alachlor, metolachlor, and chloride; (2) a chloride tracer solution was ponded around each of the water supply wells, and the shallowest monitoring well at each test site, for a period of 8 h during which the wells were continuously pumped and sampled for the tracer; and (3) nitrate-nitrogen and herbicide samples were collected from the water supply wells during the 8-h pumping period to observe contaminant variability during periods of continuous drawdown. Daily sampling revealed little temporal variability in the quality of water from the monitoring wells or the contaminated water supply wells. The monitoring wells, though limited in number, identified significant contaminant stratification within the shallow glacial drift aquifers supplying the water supply wells, and identified one water supply well that was producing water with much poorer quality than the shallow aquifer was capable of producing. The chloride tracer test was successful in distinguishing contaminant entry via preferential flow from that occurring through matrix flow in two of the case study wells, but proved ineffective on a third well where monitoring well data strongly suggested casing leakage. Nitrate-nitrogen and herbicide data showed little variability during the 8-h period of continuous well drawdown

Two Quality Assurance Measures for Pesticide Analysis of Wellwater: Degradation in Storage and GC/ELISA Comparison

At the request of Environmental Protection Agency (EPA) project coordinators, two special quality assurance components were included in a study of herbicides in rural wells in Iowa. Since the study involved daily sampling of 88 rural wells for a period of four to five weeks, it was anticipated that samples would be in refrigerated storage for up to eight weeks during which microbial and chemical activity could lead to analyte loss. The sample degradation study reported here was conducted to insure that water samples containing three herbicides (atrazine, alachlor, and metolachlor) did not undergo excessive losses during storage. Results indicate no reduction in pesticide concentrations in six refrigerated water samples analyzed weekly during an eight-week storage period

Root exudate carbon mitigates nitrogen loss in a semi-arid soil

AbstractThe need for increased food production to support the growing global population requires more efficient nutrient management and prevention of nitrogen (N) losses from both applied fertiliser and organic matter (OM) decomposition. This is particularly important in semi-arid rainfed cropping soils, where soil water and temperature are the dominant drivers of N cycling rather than agricultural management. Here we used 14C and 15N techniques to examine how peptide/amino acid turnover, gross and net N transformation rates and nitrous oxide (N2O) emissions responded to long-term plant residue additions and/or short-term root exudate additions. Soil was collected from a semi-arid rainfed field trial with one winter crop per year followed by a summer fallow period, where additional inputs of straw/chaff over 10 years had increased total soil organic C (SOC) by 76% compared to no extra additions (control). These field soils were incubated in the laboratory with or without a synthetic root exudate mixture at a range of temperatures reflecting regional field conditions (5–50 °C). Long-term plant residue additions (to build up total soil OM) did not decrease the risk of N loss as defined by the nitrification:immobilisation (N:I) ratio at most temperatures, so was not an effective management tool to control N losses. In comparison, short-term root exudate additions decreased the risk of N loss at all temperatures in both the control and plant residue treatment field soils. Increased net N mineralisation and decreased microbial C use efficiency at temperatures greater than 30 °C resulted in significant ammonium (NH4+) accumulation. Microbial decomposers appeared to use amino acid-C for growth but peptide-C for energy production. Findings indicate that the greatest risk of N loss in these semi-arid soils will occur during rains at the start of the growing season, due to inorganic N accumulation over summer fallow when there are high soil temperatures, occasional significant rainfall events and no growing plants to release root exudates. While most attempts to manipulate the soil N cycle have occurred during the winter cropping period, our findings highlight the need to manage N supply during summer fallow if we are to minimise losses to the environment from semi-arid soils

Outcomes of service encounter quality in a business-to-business context

Service encounter quality is an area of growing interest to researchers and managers alike, yet little is known about the effects of face-to-face service encounter quality within a business-to-business setting. In this paper, a psychometrically sound measure of such service encounter quality is proposed, and consequences of this construct are empirically assessed. Both a literature review and a dyadic in-depth interview approach were used to develop a conceptual framework and a pool of items to capture service encounter quality. A mail survey of customers was undertaken, and a response rate of 36% was obtained. Data analysis was conducted via confirmatory factor analysis and structural equation modeling. Findings reveal a four-factor structure of service encounter quality, encompassing professionalism, civility, friendliness and competence dimensions. Service encounter quality was found to be directly related to customer satisfaction and service quality perceptions, and indirectly to loyalty. The importance of these findings for practitioners and for future research on service encounter quality is discussed