Alasdair Noble

Massey University, Palmerston North City, Manawatu-Wanganui, New Zealand

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Publications (5)6.18 Total impact

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    ABSTRACT: A Bayesian approach was developed by Hald et al.((1)) to estimate the contribution of different food sources to the burden of human salmonellosis in Denmark. This article describes the development of several modifications that can be used to adapt the model to different countries and pathogens. Our modified Hald model has several advantages over the original approach, which include the introduction of uncertainty in the estimates of source prevalence and an improved strategy for identifiability. We have applied our modified model to the two major food-borne zoonoses in New Zealand, namely, campylobacteriosis and salmonellosis. Major challenges were the data quality for salmonellosis and the inclusion of environmental sources of campylobacteriosis. We conclude that by modifying the Hald model we have improved its identifiability, made it more applicable to countries with less intensive surveillance, and feasible for other pathogens, in particular with respect to the inclusion of nonfood sources. The wider application and better understanding of this approach is of particular importance due to the value of the model for decision making and risk management.
    Risk Analysis 08/2009; 29(7):970-84. · 2.28 Impact Factor
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    ABSTRACT: This study quantifies the spatio-temporal association between outbreaks of highly pathogenic avian influenza H5N1 in domestic poultry (n = 3050) and human cases (n = 99) in Vietnam during 2003-2007, using rare events logistic regression. After adjusting for the effect of known confounders, the odds of a human case being reported to authorities increased by a factor of 6.17 [95% confidence interval (CI) 3.33-11.38] and 2.48 (95% CI 1.20 - 5.13) if poultry outbreaks were reported in the same district 1 week and 4 weeks later respectively. When jointly considering poultry outbreaks in the same and neighbouring districts, occurrence of poultry outbreaks in the same week, 1-week later, and 4 weeks later increased the odds of a human case by a factor of 2.75 (95% CI 1.43-5.30), 2.56 (95% CI 1.31-5.00) and 2.70 (95% CI 1.56-4.66) respectively. Our study found evidence of different levels of association between human cases and poultry outbreaks in the North and the South of the country. When considering the 9-week interval extending from 4 weeks before to 4 weeks after the week of reporting a human case, in the South poultry outbreaks were recorded in 58% of cases in the same district and 83% of cases in either the same or neighbouring districts, whereas in the North the equivalent results were only 23% and 42%. The strength of the association between human and poultry cases declined over the study period. We conclude that owner reporting of clinical disease in poultry needs to be enhanced by targeted agent-specific surveillance integrated with preventive and other measures, if human exposure is to be minimized.
    Transboundary and Emerging Diseases 07/2009; 56(8):311-20. · 3.12 Impact Factor
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    ABSTRACT: The motivation for this work was to investigate the possibility of accurately determining the age of a tern chick using easily obtained body measurements. We describe the construction of a nonlinear multivariate hierarchical model for chick growth and show how it can be estimated using Markov chain Monte Carlo techniques. A simple extension of the analysis allows for estimation of the ages of unknown chicks. Posterior distributions of the unknown ages are derived, so that the accuracy of age determination can be examined. We further extend our model and analysis to include the possibility that chicks fall into distinct groups with different growth characteristics. The technique is illustrated using data on the weight and wing length of black-fronted terns from the Ohau River, New Zealand. It is found that dating to within one day is possible, but only in some areas of the data space. The concept of “braiding” of multivariate growth curves is introduced to explain the varying accuracy of age determination.
    Journal of Agricultural Biological and Environmental Statistics 09/2005; 10(3):306-320. · 0.78 Impact Factor
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    ABSTRACT: Combining data sources is often seen as a panacea, having the potential to produce more to produce cost-effective, accurate, fine-level statistics for a lower cost. This paper clarifies conditions under which Official Statistics data sources, particularly surveys and censuses or surveys and administrative sources, should and should not be combined using statistical models based on mass imputation, spatial microsimulation, and small area and domain estimation. The theoretical links between these three techniques are explored. The wider research from which this paper is a report considers the relevant literature in depth, further develops existing statistical methods, considers their application in principle to set of case studies in sociology, economics, and business, and provides guidelines for use of the three techniques based on this research.
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