World Congress on Risk 2015
19-23 July, 2015, Singapore

Online Program

Session Schedule & Abstracts

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Common abbreviations

Wednesday 22-07-2015

Emerging infectious disease: an integrated approach to assessing the risks

Room: Creation   15:30–17:00

Chair(s): Victoria Brookes

1    The risk inside: efficient resource allocation to support sustainable rabies control programmes. Del Rio Vilas VJ    (26)

Abstract: A number of countries are leading towards dog mediated rabies elimination. This is the case of south East Asian countries that aim for a 2020 regional goal. At this critical stage of the rabies epidemic, when cases are few, rabies programme managers face the diminishing relevance of dog-transmitted rabies as a public health problem and the surge of alternative competing health priorities. The combined effect of these factors, added to the chronic neglect of rabies, poses a continuous risk to rabies specific budget and resources. The need for research on the sustainability of rabies programmes is clear and stressed in earlier reports (WHO 2013). Ensuring the most efficient use of resources is an essential step to guarantee sustainability. To this end, we describe a multi-criteria decision analysis (MCDA) model to help the evaluation of rabies programmes, via partial scoring of rabies capacities and aggregation to a country-level score, and the identification of the best investment strategy for countries and territories to improve and efficiently maintain their rabies status. The MCDA model allows integration of incommensurate essential capacities for the control of rabies, at the human and animal interface, such as risk analysis and surveillance with education and stakeholder integration, and their assessment relative to other components of a comprehensive rabies control programme.

2    A tool for assessing the risk of rabies to support surveillance. Hernandez-Jover M.    (28)

Abstract: Introduction of rabies to Indonesia occurred in the 1880s, and over 2 to 3 decades it spread throughout much of the archipelago. Recently, historically rabies-free islands, including Flores, Ambon and Bali, have become infected and rabies is spreading throughout the provinces of Maluku and Northern Maluku. This spread of rabies in Indonesia poses a risk to human and animal populations in the remaining free islands, as well as the neighbouring rabies-free countries of Timor Leste, Papua New Guinea and Australia. The aim of this study was to develop a generic risk assessment tool to rapidly determine the vulnerability and risk of infection of rabies-free islands, to prioritise islands for targeted surveillance and increase the sensitivity of the surveillance system. History of rabies spread, anthropological studies, and opinions of local animal health experts were used to develop this tool, which is based on entry and exposure assessments implemented using scenario trees and Monte Carlo stochastic simulation modelling. The resulting tool was based on eight critical parameters that can be estimated from literature, expert opinion, observational studies and information from routine surveillance. Using the input parameters elicited from the participating experts, the tool predicted that rabies-infection (one infected case) might occur in a rabies–free island (upper 95% prediction interval) with a volume of 1,000 boats movements. With 25,000 boat movements, the median probability would be equal to one infected case, with a 95% of six infected cases. Model outputs were most sensitive to the probability of presence of dogs on private and fishing boats. The study recommends development of programs to determine the probability of presence of dogs in boats, such as port surveillance or surveys among fishermen and passenger ferries. Use of this generic risk assessment tool would allow the identification of high priority areas where surveillance to prevent rabies spread is critical.

3    MCDA for disease prioritisation: comparison of methods to assess decision-makers perceptions of risk. Brookes VJ    (29)

Abstract: Correct weighting of criteria in multi-criteria decision analysis (MCDA) is important to accurately reflect decision-makers’ perceptions of risk. Keeney (2002) stated that weights should be assessed within the scales of the decision context through evaluation of the trade-offs that decision-makers are prepared to make between criteria. However, criteria for MCDA in health applications are often weighted without evaluation of trade-offs and outwith the decision context. In the absence of validation or the gold standard of knowledge of the “right” decision, it is difficult to assess the accuracy of these studies and their value in predicting disease importance. MCDA was used to prioritise exotic diseases for the pig industry in Australia, and three methods to weight criteria were compared. For two methods (probabilistic inversion and a regression-based technique, Point of Truth Calibration (POTCal)), decision-makers were asked to rank and score constructed disease scenarios, 16 of which were used to derive weights, and 4 of which were used for validation. The scenarios forced decision-makers to trade-off the importance of criteria within the decision context. The third method (direct ranking) asked decision-makers to rank individual criteria outwith the decision context; weights were derived from normalised mean rank. Weighted sum MCDA models using criterion weights derived from each method were used to predict decision-makers’ ranks and scores for the validation scenarios. Models using weights derived by probabilistic inversion and POTCal closely recovered the decision-makers’ order of the validation scenarios, unlike the model using weights derived by direct ranking. We discuss the use of validation scenarios to assess the accuracy MCDA models developed for disease prioritisation, and the implications of using different methods to weight criteria on the defensible allocation of health resources.

4    A novel simulation model for investigating the control of epidemic rabies. Ward MP    (41)

Abstract: The coastal border of northern Australia is a remote area with a credible risk of rabies incursion from Indonesia. There are large populations of domestic dogs, mostly in Indigenous communities. Rabies preparedness is a priority, and infectious disease simulation models are useful tools for investigating spread, impact and effectiveness of control options. Previous rabies models have focused on endemic situations. We developed a novel stochastic spatio-temporal model for simulating rabies epidemics in domestic dog populations in high risk regions along the northern border of Australia. This model is based on individual dogs informed by dog census data and incorporates three types of rabies spread (within household, between households and between communities). Three types of control strategy are implemented in the model: a) vaccination (50 and 70% coverage); b) culling (30, 50 and 70% level); and c) movement restrictions between communities, within communities (dog confinement) or both, with dog owner compliance of 50 or 80%. Each strategy was simulated 100 times for two separate regions with either one or five communities. Outcomes were measured by the number of dogs that died, and the reproductive rate of disease spread. Vaccination was found to be most effective in reducing outbreak size, while movement bans are only effective with high compliance. Culling was found to be less effective. The median R0 ranged from 4.6 to 4.9 and decreased with increasing level of culling (R0 2.5-2.9), vaccination (R0 3.1-3.7) and ban compliance (R0 2.8-3.4). This is, to the best of our knowledge, the first time a rabies model has been applied to compare control strategies for an epidemic situation with absence of rabies prior to the simulated incursion. It provides useful knowledge for evidence-based preparedness plans in rabies-free regions, and also to manage recent incursions in both developing and developed countries.

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