Use of a multi-criteria analysis framework to inform the design of risk based general surveillance systems for animal disease in Australia

Critically appraised topic: the use of vaccination to control the spread of foot-and-mouth disease in Australian livestock in the event of an incursion

With recent outbreaks of foot-and-mouth disease (FMD) in Indonesia and Bali, industry, government and public concern for its incursion into Australia is increasing. The potential impact of an outbreak on the agricultural industry and national economy could be devastating. To date, research conducted in relation to FMD in Australia predominantly concerns simulations and models performed to predict various outcomes. This project critically appraises the current literature regarding the simulated use of vaccination and its effectiveness for controlling the spread of FMD in Australia in the event of an outbreak. Findings from 10 modelling studies suggest that vaccination is effective at controlling the size and duration of an outbreak (under certain conditions), however, there is less clarity about cost-effectiveness.

Declining engagement of veterinary services in Australian animal production systems: why has this occurred and what are the risks?

The provision of veterinary services is essential to deliver animal health and welfare outcomes, but over the last several decades demand for veterinary services in animal production systems has broadly declined in Australia. Reduced demand is closely related to a decline in the size of the production animal veterinary workforce, and there is evidence that the percentage of veterinarians participating in the delivery of veterinary services to animal production systems has lessened. Reduced demand for veterinary services in the production animal sector is likely to be attributed to several factors, including challenges around widespread adoption of preventive veterinary services, improved self-efficacy of producers through advancement of knowledge, and potential concern by producers over the role of veterinarians in production animal systems. Declining veterinary engagement results in increased risk at both the individual farm level (diminished expertise to deliver reactive and proactive veterinary services) and at a population level (increased biosecurity risk and risk to social licence to operate). The current environment and the community trust in the profession should be seen as an opportunity to develop and implement a strategy to halt and reverse the decline in demand for production animal veterinary services. Such a strategy will require significant and sustained collaboration between the veterinary profession, Industry and government.

FMD vaccine allocation and surveillance resourcing options for a potential Australian incursion

Australian Animal Disease Spread (AADIS) epidemiological simulation modelling of potential foot-and-mouth disease outbreaks in the state of Victoria, Australia examined the targeted use of limited vaccine supplies in combination with varying surveillance resources. Updated, detailed estimates of government response costs were prepared based on state level data inputs of required and available resources. Measures of outbreak spread such as duration and numbers of animals removed through depopulation of infected and vaccinated herds from the epidemiological modelling were compared to summed government response costs. This comparison illustrated the trade-offs between targeted control strategies combining vaccination-to-remove and varying surveillance capacities and their corresponding costs. For this intensive cattle and sheep producing region: (1) Targeting vaccination toward intensive production areas or toward specialized cattle operations had outbreak control and response cost advantages similar to vaccination of all species. The median duration was reduced by 27% and response costs by 11%. (2) Adding to the pool of outbreak surveillance resources available further decreased outbreak duration and outbreak response costs. The median duration was reduced by an additional 13% and response costs declined by an additional 8%. (3) Pooling of vaccine resources overcame the very early binding constraints under proportional allocation of vaccines to individual states with similar reductions in outbreak duration to those with additional surveillance resources. However, government costs rose substantially by over 40% and introduced additional risk of a negative consumer response. Increased knowledge of the outbreak situation obtained from more surveillance led to better-informed vaccination deployment decisions in the short timeframe they needed to be made.

Australian veterinarians' perspectives on the contribution of the veterinary workforce to the Australian animal health surveillance system

This study investigated the involvement of private veterinarians in surveillance activities and the veterinary workforce's contribution to the Australian animal health surveillance system. The perception that there is overall a decreased engagement by veterinarians in surveillance outcomes at a time when there is increased need for bolstering of surveillance systems was investigated. Three key questions were considered: (1) What is the current contribution of private veterinarians to the Australian surveillance system? (2) What is the veterinary professions capacity to assume a more prominent role in surveillance? (3) What is the interest and ability of the veterinary profession in Australia to undertake this surveillance role now and into the future? Semi-structured telephone interviews were conducted with 17 private veterinarians with data analyzed qualitatively to identify key themes. Results demonstrate that private veterinarians are aware of their responsibilities and are engaged in surveillance activities at both formal and informal levels. The key challenges associated with current and future contributions were related to workload, remuneration, conflicts of interest and clarity over how responsibility for surveillance is shared amongst those involved in the system. The study has demonstrated that even amongst an engaged population, barriers do need to be addressed if private veterinarians are to be tasked with increasing their involvement in animal health surveillance activities.

Novel variant Hendra virus genotype 2 infection in a horse in the greater Newcastle region, New South Wales, Australia

In October 2021, the first contemporary detection of Hendra virus genotype 2 (HeV-g2) was made by veterinary priority disease investigation in a horse near Newcastle, New South Wales, Australia, as part of routine veterinary priority disease surveillance.

This discovery followed an update of Hendra virus diagnostic assays following retrospective identification of this variant from 2015 via sentinel emerging infectious disease research, enabling timely detection of this case. The sole infected horse was euthanized in moribund condition. As the southernmost recognised HeV spill-over detection to date, it extends the southern limit of known cases by approximately 95 km. The event occurred near a large urban centre, characterised by equine populations of diverse type, husbandry, and purpose, with low HeV vaccination rates.

Urgent multi-agency outbreak response involved risk assessment and monitoring of 11 exposed people and biosecurity management of at-risk animals. No human or additional animal cases were recognised.

This One Health investigation highlights need for research on risk perception and strategic engagement to support owners confronted with the death of companion animals and potential human exposure to a high consequence virus. The location and timing of this spill-over event diverging from that established for prototype HeV (HeV-g1), highlight benefit in proactive One Health surveillance and research activities that improve understanding of dynamic transmission and spill-over risks of both HeV genotypic lineages and related but divergent emerging pathogens.

•

In October 2021 an equine case of Hendra virus genotype 2 (HeV-g2) was detected near Newcastle, Australia

•

Detection was facilitated through recent adoption by animal health of an updated PCR assay able to detect HeV-g2

•

The case occurred outside of the southern winter season typical for HeV and marks the southernmost equine detection to date

•

This event highlights the expanded geographical risk of spillover from flying-foxes to horses that is presented by HeV-g2

The epidemiology of swine influenza

Globally swine influenza is one of the most important diseases of the pig industry, with various subtypes of swine influenza virus co-circulating in the field. Swine influenza can not only cause large economic losses for the pig industry but can also lead to epidemics or pandemics in the human population. We provide an overview of the pathogenic characteristics of the disease, diagnosis, risk factors for the occurrence on pig farms, impact on pigs and humans and methods to control it. This review is designed to promote understanding of the epidemiology of swine influenza which will benefit the control of the disease in both pigs and humans.

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.

Using a Bayesian Network Predictive Model to Understand Vulnerability of Australian Sheep Producers to a Foot and Mouth Disease Outbreak

To maintain and strengthen Australia's competitive international advantage in sheep meat and wool markets, the biosecurity systems that support these industries need to be robust and effective. These systems, strengthened by jurisdictional and livestock industry investments, can also be enhanced by a deeper understanding of individual producer risk of exposure to animal diseases and capacity to respond to these risks. This observational study developed a Vulnerability framework, built from current data from Australian sheep producers around behaviors and beliefs that may impact on their likelihood of Exposure and Response Capacity (willingness and ability to respond) to an emergency animal disease (EAD). Using foot and mouth disease (FMD) as a model, a cross-sectional survey gathered information on sheep producers' demographics, and their practices and beliefs around animal health management and biosecurity. Using the Vulnerability framework, a Bayesian Network (BN) model was developed as a first attempt to develop a decision making tool to inform risk based surveillance resource allocation. Populated by the data from 448 completed questionnaires, the BN model was analyzed to investigate relationships between variables and develop producer Vulnerability profiles. Respondents reported high levels of implementation of biosecurity practices that impact the likelihood of exposure to an EAD, such as the use of appropriate animal movement documentation (75.4%) and isolation of incoming stock (64.9%). However, adoption of other practices relating to feral animal control and biosecurity protocols for visitors were limited. Respondents reported a high uptake of Response Capacity practices, including identifying themselves as responsible for observing (94.6%), reporting unusual signs of disease in their animals (91.0%) and daily/weekly inspection of animals (90.0%). The BN analysis identified six Vulnerability typologies, with three levels of Exposure (high, moderate, low) and two levels of Response Capacity (high, low), as described by producer demographics and practices. The most influential Exposure variables on producer Vulnerability included adoption levels of visitor biosecurity and visitor access protocols. Findings from this study can guide decisions around resource allocation to improve Australia's readiness for EAD incursion and strengthen the country's biosecurity system.

The goat industry in Australia: Using Bayesian network analysis to understand vulnerability to a foot and mouth disease outbreak

Australia's goat industry is one of the largest goat product exporters in the world, managing both farmed and wild caught animals. To protect and maintain the competitive advantage afforded to the Australian goat industry by the absence of many diseases endemic elsewhere, it is important to identify the vulnerability of producers to livestock disease incursions. This study developed a framework of producer vulnerability built from the beliefs and practices of producers that may impact on their likelihood of exposure and response capacity to an emergency animal disease (EAD), using foot and mouth disease as a model. A cross-sectional questionnaire gathered information on producer/enterprise demographics, animal health management and biosecurity practices, with 107 participating in the study. The biosecurity measures that were most commonly implemented by producers were always using animal movement documentation for purchased stock (74.7 %) and isolating new stock (73.1 %). However, moderate to low uptake of biosecurity protocols related to visitors to the property were reported. Response capacity variables such as checking animals daily (72.0 %) and record keeping (91.7 %) were reported by the majority of respondents, with 40.7 % reporting yearly veterinary inspection of their animals. Using the vulnerability framework, a Bayesian Network model was developed and populated by the survey data, and the relationships between variables were investigated. Six vulnerability profiles were developed, with three levels of exposure (high, moderate, low) and two levels of response capacity (high, low), as described by producer demographics and practices. The most sensitive exposure variables on producer vulnerability included implementation of visitor biosecurity and control of feral animals. Results from this study can inform risk based perspectives and decisions around biosecurity and surveillance resource allocation within the goat industry. The results also highlight opportunities for improving Australia's preparedness for a future EAD incursion by considering producer behaviour and beliefs by applying a vulnerability framework.

Identification of risk areas for foot and mouth disease in Thailand using a geographic information system-based multi-criteria decision analysis

In our study, we used geographic information system (GIS)-based multi-criteria decision analysis (MCDA) to predict suitable areas for foot and mouth disease (FMD) occurrence in Thailand. Eleven experts evaluated 10 spatial risk factors associated with the occurrence and spread of FMD in Thailand during 2014-2015. The analytic hierarchy process was used to conduct problem structuring and prioritising of pairwise comparisons with criterion weighting. Important spatial risk factors were converted to geographical layers using standardised fuzzy membership. Thus, weight linear combination was used to combine and create suitability and uncertainty maps as well as to perform sensitivity analysis. We identified areas in northern, north-eastern, western, and central Thailand as hotspots of FMD occurrence. In the predictive map, the suitable areas presented a moderate degree of agreement with those after FMD outbreaks in the year 2016 (AUC = 0.71, 95 %CI: 0.68-0.75). In conclusion, GIS-based MCDA mapping well supported veterinary services in identifying hotspot areas of FMD occurrence in Thailand. This tool was very useful for disease surveillance.

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.

Timeliness of vesicular disease notification system in Brazilian foot-and-mouth disease surveillance programme

Animal health surveillance programmes should be reliable and informative to ensure their effective implementation. As such, the regular assessment of those aiming to demonstrate the absence of disease, as well as the ability to detect outbreaks on time, is of vital importance. Several criteria make it possible to assess the performance of surveillance systems, including timeliness, which represents the speed between steps in a surveillance system. Therefore, the objective of this study was to evaluate the variability in the timeliness, within and between states, of the surveillance programme of the Brazilian Veterinary Services (BVS) for foot-and-mouth disease (FMD), for the notification of vesicular disease. A total of 14 years (2004-2017) of data relating to vesicular syndromes from the Brazilian Continental Information and Surveillance System (SivCont) were included. A categorical variable was created with four classes to group the notified vesicular processes in the SivCont, according to two criteria, the similarity of the symptoms of the diseases reported with FMD and aetiology (viral, bacterial, fungal and non-infectious). The three timeliness values (TL-1, TL-2 and TL-3) related to different portions of the FMD surveillance system were analysed as a response in a generalized linear model in which the states of Brazil were the explanatory variables. The analyses were performed separately for each notification class (FMD, vesicular stomatitis, similar symptoms and similar non-infectious symptoms) and included comparisons within and between states. The study results provide an understanding and evaluation of the timeliness of the Brazilian FMD surveillance system, thereby providing a base of knowledge from which involved agents and decision-makers can evaluate BVS and reinforce surveillance measures in the states with poorer timeliness than permitted.

Understanding the vulnerability of beef producers in Australia to an FMD outbreak using a Bayesian Network predictive model

Effective and adaptable biosecurity and surveillance systems are crucial for maintaining and increasing Australia's competitive advantages in international markets, and for the production of high quality, safe animal products. These systems are continuously strengthened by ongoing government and industry investment. However, a better understanding of evolving disease risks and the country's capacity to respond to these risks is needed. This study developed a vulnerability framework based on characteristics and behaviours of livestock producers that impact exposure and response capacity to an emergency animal disease (EAD) outbreak among beef producers in Australia, with a focus on foot and mouth disease (FMD). This framework articulated producer vulnerability typologies to better inform surveillance resource allocation and future research direction. A cross-sectional study of beef producers in Australia was conducted to gather information on producers' demographics, husbandry characteristics, biosecurity and animal health management practices and beliefs, including those specific to FMD risk and response capacity. A Bayesian Network (BN) model was developed from the vulnerability framework, to investigate the complex interrelationships between variables and identify producer typologies. A total of 375 usable responses were obtained from the cross-sectional study. Regarding EAD exposure, producers implemented appropriate biosecurity practices for incoming stock, such as isolation (72.0 %), inspection for disease (88.7 %) and the use of vendor declarations (78.5 %); however, other biosecurity practices were limited, such as restriction of visitor access, visitor biosecurity requirements or feral animal control. In relation to response capacity, a moderate uptake of practices was observed. Whilst daily or weekly visual inspection of animals was reported by most producers (90.1 %), physical inspection was less frequent. Most producers would call a private veterinarian in response to unusual signs of disease in their cattle; however, over 40 % of producers did not cite calling a government veterinarian as a priority action. Most producers believe an FMD outbreak would have extremely serious consequences; however, their level of concern was moderate and their confidence in identifying FMD symptoms was low. The BN analysis identified six vulnerability typologies, with three levels of exposure (high, moderate, low) and two levels of response capacity (high, low), as described by producer demographics and practices. The model identified property size, number of cattle and exposure variables as the most influential to the overall producer vulnerability. Results from this study can inform how to best use current biosecurity and surveillance resources and identify where opportunities exist for improving Australia's preparedness for future EAD incursions.

Sampling to elucidate the dynamics of infections in reservoir hosts

The risk of zoonotic spillover from reservoir hosts, such as wildlife or domestic livestock, to people is shaped by the spatial and temporal distribution of infection in reservoir populations. Quantifying these distributions is a key challenge in epidemiology and disease ecology that requires researchers to make trade-offs between the extent and intensity of spatial versus temporal sampling. We discuss sampling methods that strengthen the reliability and validity of inferences about the dynamics of zoonotic pathogens in wildlife hosts. This article is part of the theme issue 'Dynamic and integrative approaches to understanding pathogen spillover'.

Development and validation of a scoring system to assess the relative vulnerability of swine breeding herds to the introduction of PRRS virus

Biosecurity is defined as the set of practices carried out to prevent the introduction and spread of infectious agents in a herd. These practices are essential in swine production, especially for highly infectious agents such as porcine reproductive and respiratory syndrome virus (PRRSv). Even with years of research and experience over the last three decades, PRRSv is still causing productivity losses and is the major health problem affecting the global swine industry. Despite knowledge of the various ways in which the virus can be transmitted from one herd to another (e.g. animals, semen, truck, air, and people), determining the most frequent ways in which the virus is transmitted in the field is difficult. A systematic approach to assess vulnerabilities at a herd level related to PRRSv transmission could help producers prioritize biosecurity practices to reduce or avoid the occurrence of outbreaks. The aim of this study was to develop a biosecurity vulnerability score that represents the relative vulnerability of swine breeding herds to the introduction of PRRSv. To create the biosecurity vulnerability score (outcome), a multi-criteria decision analysis methodology was used to rank and quantify biosecurity practices based on expert opinion. To validate the biosecurity vulnerability score, a survey of biosecurity practices and PRRS outbreak histories in 125 breed-to-wean herds in the U.S. swine industry was used. Data on the frequency of PRRS outbreaks was used to test the hypothesis that biosecurity vulnerability scores were different between farms that have a low incidence of PRRS outbreaks, compared to farms that have a high incidence. In the two databases used, the scores consistently showed that farms with higher scores have a higher frequency of PRRS outbreaks. In the first validation, farms that had never had an outbreak investigation before had a significant (p < 0.02) lower score (0.29; 0.21-0.37) when compared to farms that had 2 or more outbreaks (0.43; 0.39-0.46). In the second, the farms of the control group also had significant (p < 0.004) lower scores (0.30; 0.27-0.33) compared to the case group (0.35; 0.33-0.38). Also, the results suggest that events related to swine movements, transmission by air and water, and people movements should be prioritized. The biosecurity vulnerability scores may be useful to assess vulnerabilities on biosecurity protocols in order to reduce the frequency of PRRS outbreaks and may help producers and veterinarians prioritize investments in improving biosecurity practices over time.

Stakeholder perceptions of foot-and-mouth disease control in South Africa

Foot-and-mouth disease (FMD) prevention and control is a challenge worldwide but the situation in southern Africa is particularly complex because the virus is endemic in wild African buffalo (Syncerus caffer). The objective of this study was to compare stakeholder perceptions of the FMD control methods employed to restrict FMD virus to the infected zone of South Africa. Data collection was performed using an online questionnaire distributed to FMD experts, government veterinarians, private livestock veterinarians, people involved within the wildlife sector, and "other" occupation groups including the general public. Data were also collected using semi-structured participatory group discussions with government animal health technicians (AHT) and communal cattle owners directly affected by FMD control measures. Evaluated control methods were the disease control fence bordering the western boundary of the Greater Limpopo Transfrontier Conservation Area, clinical surveillance of livestock, movement control of cloven-hoofed animals and products, and routine FMD vaccination of cattle. These management procedures were scored according to a set of technical, economic, and ethical criteria by stakeholders, who also weighted the criteria according to their perceived importance. Scores and weights were aggregated using an additive linear model to rank control methods. Sensitivity analysis was performed using a stochastic model to explore the effects of varying inputs and the exclusion of scores from randomly selected respondent groups on the ranking of control methods. The deterministic analysis assigned the highest ranking to the disease control fence and the lowest to routine vaccination of cattle. The fence had the highest ranking in 40% of the stochastic iterations, and second, third and fourth in 26%, 20% and 14% of iterations, respectively. The inputs from the AHT and people involved in the wildlife sector were the most influential for ranking the fence as the preferred control option. The most influential criteria were the feasibility of the fence as a control option and its influence on the economics of the communal cattle owners, livestock industry in the FMD free zone, and the government. The disease control fence was the highest ranking control option but further investigations are necessary to understand the reasons for stakeholder perceptions.

Quantitative risk assessment of WSSV transmission through partial harvesting and transport practices for shrimp aquaculture in Mexico

This quantitative risk assessment provided an analytical framework to estimate white spot syndrome virus (WSSV) transmission risks in the following different scenarios: (1) partial harvest from rearing ponds and (2) post-harvest transportation, assuming that the introduction of contaminated water with viral particles into shrimp culture ponds is the main source of viral transmission risk. Probabilities of infecting shrimp with waterborne WSSV were obtained by approaching the functional form that best fits (likelihood ratio test) published data on the dose-response relationship for WSSV orally inoculated through water into shrimp. Expert opinion defined the ranges for the following uncertain factors: (1) the concentrations of WSSV in the water spilled from the vehicles transporting the infected shrimp, (2) the total volume of these spills, and (3) the dilution into culture ponds. Multiple scenarios were analysed, starting with a viral load (VL) of 1×10²mL^-1 in the contaminated water spilled that reached the culture pond, whose probability of infection of an individual shrimp (P_i) was negligible (1.7×10^-7). Increasing the VL to 1×10^4.5mL^-1 and 1×10⁷mL^-1 yielded results into very low (P_i=5.3×10^-5) and high risk (P_i=1.6×10^-2) categories, respectively. Furthermore, different pond stocking density (SD) scenarios (20 and 30 post-larvae [PL]/m²) were evaluated, and the probability of infection of at least one out of the total number of shrimp exposed (P_N) was derived; for the scenarios with a low VL (1×10²mL^-1), the P_N remained at a negligible risk level (P_N, 2.4×10^-7 to 1.8×10^-6). For most of the scenarios with the moderate VL (1×10^4.5mL^-1), the P_N scaled up to a low risk category (P_N, 1.1×10^-4 to 5.6×10^-4), whereas for the scenarios with a high VL (1×10⁷mL^-1), the risk levels were high (P_N, 2.3×10^-2 to 3.5×10^-2) or very high (P_N, 1.1×10^-1 to 1.6×10^-1) depending on the volume of contaminated water spilled in the culture pond (VCWSCP, 4 or 20L). In the sensitivity analysis, for a SD of 30 PL/m², it was shown that starting with a VL of 1×10⁵mL^-1 and a VCWSCP of 12L, the P_N was moderate (1.05×10^-3). This was the threshold for greater risks, given the increase in either the VCWSCP or VL. These findings supported recommendations to prevent WSSV spread through more controlled transportation and partial harvesting practices.

Identification of foot and mouth disease risk areas using a multi-criteria analysis approach

Foot and mouth disease (FMD) is a highly infectious disease that affects cloven-hoofed livestock and wildlife. FMD has been a problem for decades, which has led to various measures to control, eradicate and prevent FMD by National Veterinary Services worldwide. Currently, the identification of areas that are at risk of FMD virus incursion and spread is a priority for FMD target surveillance after FMD is eradicated from a given country or region. In our study, a knowledge-driven spatial model was built to identify risk areas for FMD occurrence and to evaluate FMD surveillance performance in Rio Grande do Sul state, Brazil. For this purpose, multi-criteria decision analysis was used as a tool to seek multiple and conflicting criteria to determine a preferred course of action. Thirteen South American experts analyzed 18 variables associated with FMD introduction and dissemination pathways in Rio Grande do Sul. As a result, FMD higher risk areas were identified at international borders and in the central region of the state. The final model was expressed as a raster surface. The predictive ability of the model assessed by comparing, for each cell of the raster surface, the computed model risk scores with a binary variable representing the presence or absence of an FMD outbreak in that cell during the period 1985 to 2015. Current FMD surveillance performance was assessed, and recommendations were made to improve surveillance activities in critical areas.

Early Decision Indicators for Foot-and-Mouth Disease Outbreaks in Non-Endemic Countries

Disease managers face many challenges when deciding on the most effective control strategy to manage an outbreak of foot-and-mouth disease (FMD). Decisions have to be made under conditions of uncertainty and where the situation is continually evolving. In addition, resources for control are often limited. A modeling study was carried out to identify characteristics measurable during the early phase of a FMD outbreak that might be useful as predictors of the total number of infected places, outbreak duration, and the total area under control (AUC). The study involved two modeling platforms in two countries (Australia and New Zealand) and encompassed a large number of incursion scenarios. Linear regression, classification and regression tree, and boosted regression tree analyses were used to quantify the predictive value of a set of parameters on three outcome variables of interest: the total number of infected places, outbreak duration, and the total AUC. The number of infected premises (IPs), number of pending culls, AUC, estimated dissemination ratio, and cattle density around the index herd at days 7, 14, and 21 following first detection were associated with each of the outcome variables. Regression models for the size of the AUC had the highest predictive value (R² = 0.51-0.9) followed by the number of IPs (R² = 0.3-0.75) and outbreak duration (R² = 0.28-0.57). Predictability improved at later time points in the outbreak. Predictive regression models using various cut-points at day 14 to define small and large outbreaks had positive predictive values of 0.85-0.98 and negative predictive values of 0.52-0.91, with 79-97% of outbreaks correctly classified. On the strict assumption that each of the simulation models used in this study provide a realistic indication of the spread of FMD in animal populations. Our conclusion is that relatively simple metrics available early in a control program can be used to indicate the likely magnitude of an FMD outbreak under Australian and New Zealand conditions.

Comparison of alternatives to passive surveillance to detect foot and mouth disease incursions in Victoria, Australia

This study aimed to evaluate strategies to enhance the early detection of foot and mouth disease incursions in Australia. Two strategies were considered. First, improving the performance of the current passive surveillance system. Second, supplementing the current passive system with active surveillance strategies based on testing animals at saleyards or through bulk milk testing of dairy herds. Simulation modelling estimated the impact of producer education and awareness by either increasing the daily probability that a farmer will report the presence of diseased animals or by reducing the proportion of the herd showing clinical signs required to trigger a disease report. Both increasing the probability of reporting and reducing the proportion of animals showing clinical signs resulted in incremental decreases in the time to detection, the size and the duration of the outbreak. A gold standard system in which all producers reported the presence of disease once 10% of the herd showed clinical signs reduced the median time to detection of the outbreak from 20 to 15days, the duration of the subsequent outbreak from 53 to 42days and the number of infected farms from 46 to 32. Bulk milk testing reduced the median time to detection by two days and the number of infected farms by six but had no impact on the duration of the outbreak. Screening of animals at saleyards provided no improvement over the current passive surveillance system alone while having significant resource issues. It is concluded that the most effective way to achieve early detection of incursions of foot and mouth disease into Victoria, Australia is to invest in improving producer reporting.

Assessing the delay to detection and the size of the outbreak at the time of detection of incursions of foot and mouth disease in Australia

The time delay to detection of an outbreak of an emergency animal disease directly affects the size of the outbreak at detection and the likelihood that the disease can be eradicated. This time delay is a direct function of the efficacy of the surveillance system in the country involved. Australia has recently completed a comprehensive review of its general surveillance system examining regional variation in both the behaviour of modelled outbreaks of foot and mouth disease and the likelihood that each outbreak will be detected and reported to government veterinary services. The size of the outbreak and the time delay from introduction to the point where 95% confidence of detection was reached showed significant (p < 0.05) regional variation with the more remote northern areas experiencing smaller outbreaks that are less likely to spread and less likely to be reported to government services than outbreaks in the more developed southern areas of Australia. Outbreaks in the more densely populated areas may take up to 43 days until a 95% confidence of detection is achieved and at that time, the outbreak may involve up to 53 farms.

Spatial analysis of targeted surveillance for screw-worm fly (Chrysomya bezziana or Cochliomyia hominivorax) in Australia

OBJECTIVE

To assess Australia's targeted surveillance to detect an incursion of screw-worm fly (Chrysomya bezziana).

METHODS

A multi-criteria analysis shell was used to combine data on potential pathways of entry, availability of host species and environmental factors affecting survival of screw-worm fly in order to map spatial variation in the relative likelihood of a screw-worm fly incursion into Australia. Australia's current screw-worm fly surveillance activities were reviewed to determine whether they are located in the areas of highest likelihood of an incursion.

RESULTS

Under average environmental conditions, an incursion of screw-worm fly in Australia is relatively more likely to occur along the north coast, down the eastern seaboard or in the south-east. Cold winter temperatures would limit the environmental suitability for screw-worm fly survival to the north and north-east coast and adjacent inland areas. Australia's current targeted surveillance conducted by the Northern Australia Quarantine Strategy program of the Australian Department of Agriculture (adult screw-worm fly trapping and myiasis sampling) correlated well with areas considered to have a high relative likelihood of an incursion of screw-worm fly. Adult fly trapping conducted at sea ports was less well correlated.

DISCUSSION

Changes to surveillance at sea ports are proposed to better target areas considered to have a higher relative likelihood of screw-worm fly incursion. These include increasing the trapping intensity along the north and north-east coasts and shifting surveillance activity from the west coast to the south-east.