Equine Influenza Outbreak In Australia Research Articles

Evaluating the Effectiveness of Strategies for the Control of Equine Influenza Virus in the New Zealand Equine Population.

New Zealand has never experienced an equine influenza (EI) outbreak. The 2007 outbreak of EI in Australia showed that in a naïve population EI spreads rapidly and substantial efforts (in terms of movement restrictions, mass vaccination and post-vaccination surveillance) were required to achieve eradication. To control EI, it is essential that animal health authorities have well-defined strategies for containment, control and eradication in place before an incursion occurs. A spatially explicit stochastic simulation model, InterSpread Plus, was used to evaluate EI control strategies for the New Zealand situation. The control strategies considered were movement restrictions alone and movement restrictions in combination with one of three vaccination strategies beginning on day 14; suppressive, protective or targeted. The suppressive strategy involved vaccination in a 3 km radius around infected properties, while the protective strategy involved vaccination in a 7-10 km ring around infected properties. Targeted vaccination involved the vaccination of all breeding and racing properties within 20 km of an infected property. Simulations were carried out to determine the impact of timing of vaccination and earlier detection on the size of and duration of the outbreak. All three vaccination strategies implemented on day 14 resulted in between 1028 and 2161 fewer infected properties (P < 0.001), and an epidemic that was between 42 and 90 days shorter (P < 0.001) compared with movement restrictions alone. Any vaccination strategy implemented on day 7 resulted in fewer infected properties, compared with vaccination implemented on days 14 or 21. Overall, the suppressive vaccination strategy resulted in fewer infected properties. Our findings indicate that any vaccination strategy, if combined with complete movement restrictions could be effective for the control of EI, if an outbreak was to occur in New Zealand. If an outbreak were to occur, a simulation model has now been created to assist in decision-making using data from the actual outbreak.

Applying Bayesian network modelling to understand the links between on-farm biosecurity practice during the 2007 equine influenza outbreak and horse managers’ perceptions of a subsequent outbreak

Australia experienced its first ever outbreak of equine influenza in August 2007. Horses on 9359 premises were infected over a period of 5 months before the disease was successfully eradicated through the combination of horse movement controls, on-farm biosecurity and vaccination. In a previous premises-level case-control study of the 2007 equine influenza outbreak in Australia, the protective effect of several variables representing on-farm biosecurity practices were identified. Separately, factors associated with horse managers’ perceptions of the effectiveness of biosecurity measures have been identified.In this analysis we applied additive Bayesian network modelling to describe the complex web of associations linking variables representing on-farm human behaviours during the 2007 equine influenza outbreak (compliance or lack thereof with advised personal biosecurity measures) and horse managers’ perceptions of the effectiveness of such measures in the event of a subsequent outbreak. Heuristic structure discovery enabled identification of a robust statistical model for 31 variables representing biosecurity practices and perceptions of the owners and managers of 148 premises.The Bayesian graphical network model we present statistically describes the associations linking horse managers’ on-farm biosecurity practices during an at-risk period in the 2007 outbreak and their perceptions of whether such measures will be effective in a future outbreak. Practice of barrier infection control measures were associated with a heightened perception of preparedness, whereas horse managers that considered their on-farm biosecurity to be more stringent during the outbreak period than normal practices had a heightened perception of the effectiveness of other measures such as controlling access to the premises. Past performance in an outbreak setting may indeed be a reliable predictor of future perceptions, and should be considered when targeting infection control guidance to horse owners and managers.

Understanding the associations between on-farm biosecurity practice and equine influenza infection during the 2007 outbreak in Australia

In a previous premises-level case-control study of the 2007 equine influenza outbreak in Australia, the protective effect of several variables representing on-farm biosecurity practices was identified. However, using logistic regression it was not possible to definitively identify individual effects and associations between each of the personal biosecurity measures implemented by horse premises owners and managers in the face of the outbreak. In this study we apply Bayesian network modelling to identify the complex web of associations between these variables, horse premises infection status and other premises-level covariates.We focussed this analysis primarily on the inter-relationship between the nine variables representing on-farm personal biosecurity measures (of people residing on the premises and those visiting), and all other variables from the final logistic regression model of our previous analysis. Exact structure discovery was used to identify the globally optimal model from across the landscape of all directed acyclic graphs possible for our dataset. Bootstrapping was used to adjust the model for over-fitting.Our final Bayesian graphic network model included 18 variables linked by 23 arcs, each arc analogous to a single multivariable generalised linear model, combined in a probabilistically coherent way. Amongst the personal biosecurity measures, having a footbath in place, certain practices of visitors (hand-washing, changing clothes and shoes) in contact with the horses, and the regularity of horse handling were statistically associated with premises infection status.The results of this in-depth analysis provide new insight into the complex web of direct and indirect associations between risk factors and horse premises infection status during the first 7 weeks of the 2007 equine influenza outbreak in Australia. In future outbreaks, unnecessary contact and handling of horses should be avoided, especially by those coming from off the premises. Prior to any such contact, persons handling horses should use a footbath (if present), change their clothes and shoes, and wash their hands.

Horse owners’/managers’ perceptions about effectiveness of biosecurity measures based on their experiences during the 2007 equine influenza outbreak in Australia

Following the first ever equine influenza outbreak in Australia in 2007, a study was conducted involving 200 horse owners and managers to determine their perceptions about effectiveness of biosecurity measures and the factors associated with these perceptions. Face-to-face interviews were conducted with horse owners/managers to obtain information about their perceptions of the effectiveness of biosecurity practices, their sources of information about infection control during the outbreak and their horse industry involvement. Two outcome variables were created from horse owners’ responses to a 17-item question on the perceived effectiveness of various recommended equine influenza biosecurity measures: (a) a binary outcome variable (Low/High biosecurity effectiveness) and (b) a continuous outcome variable (the proportion of the 17 measures considered ‘very effective’). These outcomes were used in binomial logistic and linear regression analyses, respectively, to determine factors associated with perceptions of biosecurity effectiveness. Variables with a p-value <0.05 in multivariable models were retained in the final models.The majority (83%) of the 200 horse owners and managers interviewed believed that more than half of the recommended equine influenza biosecurity measures were very effective for protecting their horses from equine influenza infection in the event of a future outbreak. Interviewees that were more likely to judge on-farm biosecurity measures as effective were those who received infection control information from a veterinarian during the outbreak, did not experience equine influenza infection in their horses, and those on small acreage premises (homes with horses on site). Greater levels of preparedness for a future equine influenza outbreak and greater interest in information about infection control were associated with a better perception about effectiveness of biosecurity measures.This study identified factors associated with horse owners’ and managers’ perception of effectiveness of biosecurity measures. These findings should be considered in the design of infection control programs.

From the Horse’s Mouth: Perceptions of the Management of the 2007 Equine Influenza Outbreak in Australia

In August 2007, Australia experienced its first-ever outbreak of equine influenza, a highly infectious respiratory disease of horses. Although the outbreak spread over a large geographic area, it was eradicated within 5 months following a substantial disease control effort led by federal and state animal health authorities. Despite its timely control, this large-scale outbreak caused severe impacts on horse owners and industry participants. This study aimed to describe the perceptions of horse owners and managers, impacted by outbreak control measures, regarding the state government's animal health authority outbreak management. Participants were interviewed face-to-face. Factors associated with ordinal ratings of perception ('well managed', 'adequately managed' and 'poorly managed') were identified using ordinal logistic regression. Factors significantly associated with a reduced likelihood of 'well-managed' outbreak response ratings, adjusted for age and gender, were being involved in horse competitions/sporting events (OR = 0.48; 95% CI: 0.25-0.91), managing a horse stud (OR = 0.09; 95% CI: 0.03-0.28) and believing that another outbreak of equine influenza was highly likely in the next 5 years (OR = 0.29; 95% CI: 0.12-0.68). Possible reasons for these ratings were further investigated using content analyses. Outbreak communications and government efficiency/support were mentioned most frequently as both strengths (30% and 28%, respectively) and weaknesses (40% and 30%, respectively) of the outbreak management. To promote manager-government rapport and future compliance with disease control regulations, we recommend that outbreak communications and outbreak information systems be reviewed.

Horse owners’ biosecurity practices following the first equine influenza outbreak in Australia

A cross-sectional study was conducted involving 759 Australian horse owners to determine their biosecurity practices and perceptions one year after the 2007 equine influenza outbreak and to investigate the factors influencing these perceptions and practices. A web link to an online questionnaire was sent to 1224 horse owners as a follow-up to a previous study to obtain information about biosecurity perceptions and practices, impacts of the 2007 EI outbreak, demographic information and information about horse industry involvement. Ordinal logistic regression analyses were conducted to determine factors associated with poor biosecurity practices. Biosecurity compliance (low, medium, high), as determined by horse owners’ responses to a 16-item question on the frequency of various biosecurity measures, was used as the outcome variable in ordinal logistic regression analyses. Variables with a univariable p-value ≤0.2 were eligible for inclusion in multivariable models built using a manual stepwise approach. Variables with a p-value <0.05 in multivariable models were retained in the final model. Two potential confounders – age and gender of participants – were included in the final model irrespective of their p-values. Thirty percent of the respondents had low biosecurity compliance and were performing biosecurity practices ‘not very often’ or ‘never’. Younger people, people with two or more children, those who were not involved with horses commercially and those who had no long-term business impacts resulting from the 2007 EI outbreak were more likely to have lower biosecurity compliance. People who were not fearful of a future outbreak of equine influenza in Australia and those who thought their current hygiene and access control practices were not very effective in protecting their horses also had poor biosecurity practices. In this observational study we identified factors associated with a group of horse owners with low levels of biosecurity compliance. As this cross-sectional study only assesses associations, the identified factors should be further investigated in order to be considered in the design of extension activities to increase horse owners’ biosecurity compliance.

The importance of location in contact networks: Describing early epidemic spread using spatial social network analysis

This paper explores methods for describing the dynamics of early epidemic spread and the clustering of infected cases in space and time when an underlying contact network structure is influencing disease spread. A novel method of describing an epidemic is presented that applies social network analysis to characterise the importance of both spatial location and contact network position. This method enables the development of a model of how these clusters formed, incorporating spatial clustering and contact network topology. Based on data from the first 30 days of the 2007 equine influenza outbreak in Australia, clusters of infected premises (IPs) were identified and delineated using social network analysis to integrate contact-tracing and spatial relationships. Clusters identified by this approach were compared to those detected using the space-time scan statistic to analyse the same data. To further investigate the importance of network and spatial location in epidemic spread, kriging by date of onset of clinical signs was used to model the spatio-temporal spread without reference to underlying contact network structure. Leave-one-out cross-validation was used to derive a summary estimate of the accuracy of the kriged surface. Observations poorly explained by the kriged surface were identified, and their position within the contact network was explored to determine if they could be better explained through analysis of the underlying contact network. The contact network was found to lie at the core of a combined network model of spread, with infected horse movements connecting spatial clusters of infected premises. Kriging was imprecise in describing the pattern of spread during this early phase of the outbreak (explaining only 13% of the variation in date of onset of IPs), because early dissemination was dominated by network-based spread. Combined analysis of spatial and contact network data demonstrated that over the first 30 days of this outbreak local spread emanated outwards from the small number of infected premises in the contact network, up to a distance of around 15 km. Consequently, when a contact network structure underlies epidemic spread, we recommend applying a method of spatial analysis that incorporates the network component of disease spread. Linking the spatial and network analysis of epidemics facilitates inference of the methods of disease transmission, providing a description of the sequence of spatial cluster formation.

Insights into the economic consequences of the 2007 equine influenza outbreak in Australia

We estimate and describe the financial costs of the equine influenza (EI) outbreak in Australia, including the costs of emergency response measures and lost income/assets to businesses, associations and private horse owners. Costs to associations, governments and industry are discussed. We identify a lack of reliable data about the financial costs of the EI outbreak to the non-racing sectors of the horse industry.

Role of the diagnostic laboratories during the 2007 equine influenza outbreak in Australia

During the 2007 equine influenza (EI) outbreak in Australia, diagnostic laboratories and the use of appropriate tests played a pivotal role in the response to the crisis. This role began with the detection of EI virus in New South Wales (NSW) on the evening of 24 August 2007 and culminated in providing the final 'proof of freedom' from EI in March 2008. The tests that were used during the EI response were able to provide results quickly, and with high sensitivity and specificity. This section of the supplement describes the roles and functions of the Australian laboratories; tests used and their performance characteristics; improvements made and methods used to validate assays; strategies that were followed during the response; the characterisation of viruses detected; and the resources that were available to laboratories.

Role of the New South Wales Department of Primary Industries' Laboratory Information Management System (LIMS) in the 2007 equine influenza emergency animal disease response

A Laboratory Information Management System (LIMS) was used to manage the laboratory data and support planning and field activities as part of the response to the equine influenza outbreak in Australia in 2007. The database structure of the LIMS and the system configurations that were made to best handle the laboratory implications of the disease response are discussed. The operational aspects of the LIMS and the related procedures used at the laboratory to process the increased sample throughput are reviewed, as is the interaction of the LIMS with other corporate systems used in the management of the response. Outcomes from this tailored configuration and operation of the LIMS resulted in effective provision and control of the laboratory and laboratory information aspects of the response. The extent and immediate availability of the information provided from the LIMS was critical to some of the activities of key operatives involved in controlling the response.

Vaccination program in the response to the 2007 equine influenza outbreak in Australia

At the time of the initial notification of the occurrence of equine influenza (EI) in Australia in August 2007, vaccination was restricted to horses for which it was an import requirement and only with the approval of the state or territory Chief Veterinary Officer. This paper describes the complexities involved in the selection of a vaccine and its distribution. A combination of ring, predictive and blanket vaccination was implemented during the response. The specific vaccination programs, including its use in buffer zones and for movement of horses, the performance of the vaccine, any adverse reactions and the effect on exposure of vaccinated horses to circulating virus, are also described. Vaccination is considered to have made a valuable contribution to the containment and subsequent eradication of EI from Australia and to risk management in the resumption of horse activities in affected areas from December 2007. Movement restrictions and other biosecurity measures were critically important in controlling the spread of EI and contributing to its eventual eradication, and vaccination was an aid to these measures.

The first five days: field and laboratory investigations during the early stages of the equine influenza outbreak in Australia, 2007

Until August 2007, Australia was one of only three countries internationally recognised to be free of equine influenza (EI). This report documents the diagnosis of the first cases of EI in Australian horses and summarises the investigations that took place over the next 5 days. During that time, a multifocal outbreak was identified across eastern New South Wales and south-eastern Queensland. The use of an influenza type A pan-reactive real-time reverse transcription polymerase chain reaction allowed rapid confirmation of suspect cases of EI.

Influenza Virus Transmission from Horses to Dogs, Australia

During the 2007 equine influenza outbreak in Australia, respiratory disease in dogs in close contact with infected horses was noted; influenza (H3N8) virus infection was confirmed. Nucleotide sequence of the virus from dogs was identical to that from horses. No evidence of dog-to-dog transmission or virus persistence in dogs was found.