The economic benefits of targeted response strategies against foot-and-mouth disease in Australia.

Recent developments in control of highly infectious diseases attempt to improve emergency response efforts by more clearly focusing or targeting response tools according to risk. For example, advances in surveillance testing and sampling deliver their results by more accurately and precisely targeting the population of interest. In this work, targeted implementation of trading zones and vaccination were examined for simulated outbreaks of foot-and-mouth disease (FMD) in Australia. Trading zones allowing unaffected Australian states to resume exports following an outbreak of FMD were assessed using multiple tools. A Victorian incursion scenario with traditional stamping out and vaccination as control options, was simulated using the AADIS model Version 2.47, to characterise the geographic extent of potential outbreaks, the number of animals infected, and the date of last cull indicating duration of the outbreak. Information on disease spread from the AADIS simulations was then used to identify the boundaries of trading zones for the incursion scenario, in which vaccination with trading zones was found to further reduce disease impacts relative to stamping out alone with trading zones. The number of animals culled due to disease provided supply shocks for stamping out alone and vaccinate-to-retain, while the number of vaccinated animals was added to the number of animals culled due to disease for the supply shock of vaccinate-to-remove. The day of last cull was combined with historical FMD trade recovery and Australian export data to estimate the share of Australian exports that would be embargoed under trading zones. The market impacts - changes in equilibrium quantities and prices - of the supply shock, trading zones, and consumer reactions - were simulated within ABARES' AgEmissions partial equilibrium model of Australian agriculture. For this simulated large outbreak, where vaccinate-to-remove was utilised along with trading zones, producer losses were reduced by AUD 4 billion in present value terms over 10 years estimated at a 7% discount rate (PV10,7%) compared to an outbreak where stamping out alone is applied with trading zones. Introducing FMD virus risk mitigation measures for wool to further target trading zones reduced the economic impacts by an additional AUD 3.6 billion (PV10,7%). Outbreak response cost savings and additional potential costs under vaccinate-to-retain with trading zones were also compared to the vaccinate-to-remove control with trading zones. Results emphasised the importance of outbreak characteristics in determining trading zones and targeting of vaccination. Economic analyses identified how additional investments in targeting outbreak response is of value to producers.

Development of a transboundary model of livestock disease in Europe.

Epidemiological models of notifiable livestock disease are typically framed at a national level and targeted for specific diseases. There are inherent difficulties in extending models beyond national borders as details of the livestock population, production systems and marketing systems of neighbouring countries are not always readily available. It can also be a challenge to capture heterogeneities in production systems, control policies, and response resourcing across multiple countries, in a single transboundary model. In this paper, we describe EuFMDiS, a continental-scale modelling framework for transboundary animal disease, specifically designed to support emergency animal disease planning in Europe. EuFMDiS simulates the spread of livestock disease within and between countries and allows control policies to be enacted and resourced on a per-country basis. It provides a sophisticated decision support tool that can be used to look at the risk of disease introduction, establishment and spread; control approaches in terms of effectiveness and costs; resource management; and post-outbreak management issues.

Comparing surveillance approaches to support regaining free status after a foot-and-mouth disease outbreak.

Following an FMD eradication program, surveillance will be required to demonstrate that the program has been successful. The World Organization for Animal Health (OIE) provides guidelines including waiting periods and appropriate surveillance to support regaining FMD-free status. Serological surveillance is the recommended method for demonstrating freedom but is time consuming and expensive. New technologies such as real-time reverse transcription polymerase chain reaction (RT-qPCR) tests and sampling techniques such as bulk milk testing (BMT) of dairy cattle, oral swabs, and saliva collection with rope tethers in piggeries could enable surveillance to be done more efficiently. Epidemiological modelling was used to simulate FMD outbreaks, with and without emergency vaccination as part of the response, in Australia. Baseline post-outbreak surveillance approaches for unvaccinated and vaccinated animals based on the European FMD directive were compared with alternative approaches in which the sampling regime, sampling approaches and/or the diagnostic tests used were varied. The approaches were compared in terms of the resources required, time taken, cost, and effectiveness i.e., ability of the surveillance regime to correctly identify the infection status of herds. In the non-vaccination scenarios, the alternative approach took less time to complete and cost less, with the greatest benefits seen with larger outbreaks. In vaccinated populations, the alternative surveillance approaches significantly reduced the number of herds sampled, the total number of tests done and costs of the post-outbreak surveillance. There was no reduction in effectiveness using the alternative approaches, with one of the benefits being a reduction in the number of false positive herds. Alternative approaches to FMD surveillance based on non-invasive sampling methods and RT-qPCR tests have the potential to enable post outbreak surveillance substantiating FMD freedom to be done more quickly and less expensively than traditional approaches based on serological surveys.

Optimal surveillance against foot-and-mouth disease: A sample average approximation approach.

Decisions surrounding the presence of infectious diseases are typically made in the face of considerable uncertainty. However, the development of models to guide these decisions has been substantially constrained by computational difficulty. This paper focuses on the case of finding the optimal level of surveillance against a highly infectious animal disease where time, space and randomness are fully considered. We apply the Sample Average Approximation approach to solve our problem, and to control model dimension, we propose the use of an infection tree model, in combination with sensible 'tree-pruning' and parallel processing techniques. Our proposed model and techniques are generally applicable to a number of disease types, but we demonstrate the approach by solving for optimal surveillance levels against foot-and-mouth disease using bulk milk testing as an active surveillance protocol, during an epidemic, among 42,279 farms, fully characterised by their location, livestock type and size, in the state of Victoria, Australia.

Management strategies for vaccinated animals after an outbreak of foot-and-mouth disease and the impact on return to trade.

An incursion of Foot-and-mouth disease (FMD) in a previously FMD-free country can cause significant economic damage from immediate and prolonged closure of FMD-sensitive markets. Whilst emergency vaccination may help contain disease, the presence of vaccinated animals complicates post-outbreak management and the recovery of FMD-free status for return to trade. We present enhancements to the Australian Animal DISease (AADIS) model that allow comparisons of post-outbreak management strategies for vaccinated animals, for the purposes of securing the earliest possible return to trade. Two case studies are provided that compare the retention of vaccinated animals with removal for waste/salvage, and the impact on recovery of FMD-sensitive markets per OIE guidelines. It was found that a vaccinate-and-retain strategy was associated with lower post-outbreak management costs, however this advantage was outweighed by significantly higher trade losses. Under the assumptions of the study there was no cost advantage to salvaging the removed vaccinated animals.

A framework for reviewing livestock disease reporting systems in high-risk areas: assessing performance and perceptions towards foot and mouth disease reporting in the Thrace region of Greece, Bulgaria and Turkey.

Disease reporting is an essential frontline component of surveillance systems, particularly for detecting incursions of new and emerging diseases. It has the advantages of being comprehensive and continuous, with the potential to reduce the time of disease detection and the extent of consequent spread. A number of exotic diseases, including sheep and goat pox, lumpy skin disease, peste des petits ruminants and foot and mouth disease have historically entered into south-eastern Europe through the Thrace region, which extends across neighbouring areas of Greece, Bulgaria and Turkey. In this high-risk area, multiple factors can reduce the sensitivity of disease reporting across the diverse production systems and animal health services need robust and effective disease reporting systems. While describing a training exercise designed to provide animal health services of the three countries with the knowledge and skills for conducting comprehensive in-country assessments, we provide an initial evaluation of the sensitivity of foot and mouth disease reporting and identify gaps and constraints in the Thrace region. An expert elicitation approach was used to consult official veterinarians from central and local animal health authorities of the three countries, and scenario trees modelling was applied to analyse the collected data. The reported sensitivity of disease reporting often varied between the central and local veterinary authorities within the three countries. Awareness of clinical disease, of reporting procedures and of biosecurity measures affected the early stages of disease reporting, particularly in the production systems identified at lower reporting sensitivity such as small ruminant's herds, mixed bovine herds and backyard herds. Despite its limitations this training exercise provided an effective framework (a) to develop capacities of the veterinary services in the region and (b) to supply initial evidence for guiding further interventions targeting those sectors and stakeholders at lower reporting sensitivity to reduce risks of disease introduction.

Ensemble modelling and structured decision-making to support Emergency Disease Management.

Epidemiological models in animal health are commonly used as decision-support tools to understand the impact of various control actions on infection spread in susceptible populations. Different models contain different assumptions and parameterizations, and policy decisions might be improved by considering outputs from multiple models. However, a transparent decision-support framework to integrate outputs from multiple models is nascent in epidemiology. Ensemble modelling and structured decision-making integrate the outputs of multiple models, compare policy actions and support policy decision-making. We briefly review the epidemiological application of ensemble modelling and structured decision-making and illustrate the potential of these methods using foot and mouth disease (FMD) models. In case study one, we apply structured decision-making to compare five possible control actions across three FMD models and show which control actions and outbreak costs are robustly supported and which are impacted by model uncertainty. In case study two, we develop a methodology for weighting the outputs of different models and show how different weighting schemes may impact the choice of control action. Using these case studies, we broadly illustrate the potential of ensemble modelling and structured decision-making in epidemiology to provide better information for decision-making and outline necessary development of these methods for their further application.

Airborne spread of foot-and-mouth disease--model intercomparison.

Foot-and-mouth disease virus (FMDV) spreads by direct contact between animals, by animal products (milk, meat and semen), by mechanical transfer on people or fomites and by the airborne route, with the relative importance of each mechanism depending on the particular outbreak characteristics. Atmospheric dispersion models have been developed to assess airborne spread of FMDV in a number of countries, including the UK, Denmark, Australia, New Zealand, USA and Canada. These models were compared at a Workshop hosted by the Institute for Animal Health/Met Office in 2008. Each modeller was provided with data relating to the 1967 outbreak of FMD in Hampshire, UK, and asked to predict the spread of FMDV by the airborne route. A number of key issues emerged from the Workshop and subsequent modelling work: (1) in general all models predicted similar directions for livestock at risk, with much of the remaining differences strongly related to differences in the meteorological data used; (2) determination of an accurate sequence of events on the infected premises is highly important, especially if the meteorological conditions vary substantially during the virus emission period; (3) differences in assumptions made about virus release, environmental fate and susceptibility to airborne infection can substantially modify the size and location of the downwind risk area. All of the atmospheric dispersion models compared at the Workshop can be used to assess windborne spread of FMDV and provide scientific advice to those responsible for making control and eradication decisions in the event of an outbreak of disease.

The equine influenza epidemic in Australia: spatial and temporal descriptive analyses of a large propagating epidemic.

Australia experienced a large outbreak of equine influenza in August 2007. Nearly 10000 premises were infected during the epidemic. We used spatial and temporal analytical techniques to describe the epidemic, to quantify important descriptors of the epidemic, and to generate hypotheses about how the epidemic progressed and which control tools assisted in eradication. Spatio-temporal epidemic curves revealed three phases in the epidemic: dispersal, local spread and disease fade out. Spatial dispersal of infection rapidly declined immediately after national movement restrictions were introduced. The epidemic peak had passed before emergency vaccination could have induced substantial immunity in the equine population. Thirty seven clusters of epidemiologically linked premises were delineated using an interpolated surface of date of onset of clinical signs, geographic data and location of infected premises. These clusters were analysed individually to parameterise key epidemic measures: cumulative incidence, incidence rate, effective reproduction rate, nearest neighbour spread distances, epidemic length and the number of infected premises. These measures were summarised by landscape (rural versus peri-urban location) and standardised by disease management zone. Compared to rural areas, peri-urban areas appeared to have a higher density of equine premises (4.66 premises km(-2) versus 0.80 premises km(-2)), longer epidemics (95 days versus 87 days), more infected premises (393 versus 339) and a shorter spread distance (1.27 km versus 2.38 km). However, effective reproduction rates (2.04 versus 1.99), cumulative incidence (27.4 versus 26.9) and incidence rates (1.36 versus 1.54) were similar. The relative impact of vaccination and national movement restrictions in controlling this epidemic needs further investigation.

Identifying areas of Australia at risk of H5N1 avian influenza infection from exposure to migratory birds: a spatial analysis.

Since 2003, highly pathogenic avian influenza (HPAI) due to H5N1 virus has been reported from both domestic poultry and wild birds in 60 countries resulting in the direct death or slaughter of over 250,000,000 birds. The potential exists for HPAI to spread to Australia via migratory shorebirds returning from Asia with the most likely pathway of introduction into commercial poultry flocks involving the transfer of HPAI from migrating shorebirds to native waterfowl species that subsequently interact with poultry on low security poultry farms. Surveillance programmes provide an important early-warning for Australia's estimated 2,000 commercial poultry farms but, to be efficient, they should be risk-based and target resources at those areas and sectors of the industry at higher risk of exposure. This study compared the distributions of migratory shorebirds and native waterfowl to identify six regions where the likelihood of exotic HPAI incursion and establishment in native waterfowl is highest. Analysis of bird banding records showed that native waterfowl did not move further than 10 km during the spring breeding season when migratory shorebirds arrived in Australia. Therefore, poultry farms within 10 km of significant shorebird habitat in these six regions of highest comparative risk were identified. The final analysis showed that the estimated risk to Australia is low with only two poultry farms, one at Broome and one at Carnarvon, located in the regions of highest risk.

A review of geospatial and ecological factors affecting disease spread in wild pigs: considerations for models of foot-and-mouth disease spread.

Around the world, wild boar or feral pigs are infected by a range of infectious organisms with important, productivity, public health or economic consequences. Consequently, the potential role of wild pigs in outbreaks of important exotic diseases, like foot-and-mouth disease (FMD), has been a significant consideration in many countries. Disease modelling is one means to study the epidemiology of disease and has been used to assess the potential role of wild pigs in FMD incursions. Many of these models have been strategic in nature. They have contributed to a broad understanding of disease control in wild pigs (e.g. the concept of threshold densities and the need to cull pigs below this density for disease fadeout to occur), but have not incorporated many of the key drivers affecting disease behaviour. Some of these drivers include important ecological, behavioural and geospatial relationships, such as interaction between different host species and the distribution, density and connectivity of pig populations. New approaches to modelling disease spread such as spatial simulation models use spatial data and explicitly incorporate geospatial relationships. These approaches can provide useful quantitative models that can be used to explore mitigation strategies under specific disease outbreak conditions. However, to date, most studies have been limited by inadequate data, and computational issues or have not explored mitigation strategies. To inform management strategies for emergency epidemics such as FMD in wild pigs, there is scope to further develop and use models to explore a range of incursion scenarios and investigate the efficacy of different mitigation strategies.

Using GIS to create synthetic disease outbreaks.

BACKGROUND: The ability to detect disease outbreaks in their early stages is a key component of efficient disease control and prevention. With the increased availability of electronic health-care data and spatio-temporal analysis techniques, there is great potential to develop algorithms to enable more effective disease surveillance. However, to ensure that the algorithms are effective they need to be evaluated. The objective of this research was to develop a transparent user-friendly method to simulate spatial-temporal disease outbreak data for outbreak detection algorithm evaluation. A state-transition model which simulates disease outbreaks in daily time steps using specified disease-specific parameters was developed to model the spread of infectious diseases transmitted by person-to-person contact. The software was developed using the MapBasic programming language for the MapInfo Professional geographic information system environment. RESULTS: The simulation model developed is a generalised and flexible model which utilises the underlying distribution of the population and incorporates patterns of disease spread that can be customised to represent a range of infectious diseases and geographic locations. This model provides a means to explore the ability of outbreak detection algorithms to detect a variety of events across a large number of stochastic replications where the influence of uncertainty can be controlled. The software also allows historical data which is free from known outbreaks to be combined with simulated outbreak data to produce files for algorithm performance assessment. CONCLUSION: This simulation model provides a flexible method to generate data which may be useful for the evaluation and comparison of outbreak detection algorithm performance.