Research Article: An economic analysis of a contingency model utilising vaccination for the control of equine influenza in a non-endemic country

Date Published: January 24, 2019

Publisher: Public Library of Science

Author(s): Sarah M. Rosanowski, Tim E. Carpenter, David Adamson, Chris W. Rogers, Patricia Pearce, Martin Burns, Naomi Cogger, Massimo Giangaspero.


Equine influenza (EI) is an infectious respiratory disease of horses that has never been reported in New Zealand (NZ). However, the 2007 EI outbreak in Australia, previously EI free, spurred the NZ government and stakeholders into evaluating alternative EI control strategies in order to economically justify any future decision to eradicate or manage EI. To build on the policy debate, this paper presents an epinomic (epidemiologic and economic) modelling approach to evaluate alternative control strategies. An epidemiologic model to determine how alternative EI control strategies influence the distribution of EI. Model results were then input into a cost-benefit analysis framework, to identify the return and feasibility of alternative EI eradication strategies in NZ.

The article explores nine alternative eradication scenarios and two baseline strategies. The alternative scenarios consisted of three vaccination strategies (suppressive, protective or targeted) starting at three time points to reflect the commercial breeding-cycle. These alternatives were compared to two breeding-cycle adjusted baselines: movement restriction in the breeding season (August to January) or non-breeding season (February to July). The economic loss parameters were incursion response, impact to the commercial racing industry (breeding, sales and racing), horse morbidity and mortality, and compensation to industry participants.

Results suggest that the economic viability of the EI eradication programme is dependent on when within the breeding-cycle the EI outbreak occurs. If an outbreak were to occur, the return on each dollar invested for protective or suppressive vaccination strategies would be between NZD$3.67 to NZD$4.89 and between NZD$3.08 to NZD$3.50 in the breeding and non-breeding seasons, respectively. Therefore, protective or suppressive vaccination strategies could be prioritised, regardless of season. As multiple industry stakeholders benefit from these strategies, the study will enable policy development and to better formulate a user-pays eradication programme.

Partial Text

Equine influenza (EI) is a highly contagious respiratory illness affecting all members of the Equidae family, including horses, donkeys and mules [1, 2]. While EI is endemic worldwide, New Zealand (NZ), Iceland and Australia are currently EI free [3]. However, in August 2007, an outbreak of EI occurred in the naïve equine population in Australia [4, 5]. During that outbreak, EI spread rapidly between horses and horse properties, resulting with the Australian Government spending AUD$100 million to eradicate EI and allocating an additional AUD$260 million to support the industry [6]. The outbreak was eradicated through the implementation of movement restrictions, the cancellation of equine events such as race meetings and sport horse competitions, and by a pro-active campaign of vaccinating at-risk horses [4]. However, the true cost of the Australian EI outbreak remains unknown as the disruption to the normal equine activities has not been fully quantified [7].

Evidenced based policy is generated by merging scientific findings into economic platforms to help illustrate the consequences of real trade-offs, in order to inform social debate. This paper combines an epidemiologic and economic model in an epinomic framework to rationalise outcomes from alternative policy choices. Findings from the updated epidemiologic model are used to shape the EI scenarios and provide data to justify the assumptions used in the economic platform. This two stage modelling process then helps provide the necessary scientific and economic rigour required to evaluate changes in economic welfare from evidenced based policy [14].

The overall loss was highest under the baseline strategy for an outbreak in the breeding season ($225.5 million) and in the non-breeding season ($174.9 million) (Table 4). The additional cost of vaccination (CV) was $24.8 million, $27.0 million and $36.6 million for suppressive, protective and targeted vaccination strategies, respectively. The NB of the suppressive strategy was $96.3 million if it were implemented between August and October, and $62.1 million if it were implemented in the non-breeding season. The net benefit of the protective strategy was $89.4 million if it were implemented between August and October, and $58.4 million if it were implemented in the non-breeding season. The net benefit of the targeted strategy was $20.1 million if it were implemented between August and October, and $3.5 million if it were implemented in the non-breeding season.

This study attempts to quantify the economic impact of an EI outbreak on the NZ equine industry and provide a rationale for vaccination in the face of an outbreak. The CBA conducted here, supports the implementation of suppressive or protective vaccination, particularly if an outbreak were to occur during the breeding season. Further, the economic benefit of protective and suppressive vaccination strategies was greater if an outbreak was to occur in the breeding season (August to January), as opposed to outbreaks occurring from February to July. Nevertheless, these strategies could be prioritised based on both the reduced outbreak size, in terms of duration and number of infected properties [8] and the reduced cost to stakeholders. For example, while implementing the protective vaccination strategy was less economically efficient if it were applied in the non-breeding season, it was epidemiologically efficient compared to the baseline strategy as it shortened the overall length of the outbreak, resulting in fewer vaccinated and infected horses. A shorter outbreak will allow the more rapid resumption of normal activity, allowing for more wide-reaching benefits than have been simulated within the current framework. In contrast, the targeted strategy, where only horses involved in the racing industry were vaccinated, would be of greater cost than the baseline and not reduce the duration or size of the outbreak markedly. The targeted strategy could allow the movement of vaccinated horses to race meetings and between stud farms, a possibility that was not considered in the epidemiologic model [8] or within the economic simulation.

The outbreak of EI in Australia in 2007 and the closeness and similarity of the two equine industries, forced NZ decision makers to consider the possible implications of EI to the NZ equine industry. The implementation of suppressive or protective vaccination strategies, particularly if an outbreak were to occur during the breeding season, was found to be economically favourable when compared with the baseline strategy. This study has identified that multiple industry stakeholders, particularly those in the racing sector, will benefit from the implementation of vaccination strategies. In some scenarios, these benefits were disproportionate to the cost of an incursion response. The study will support policy development to prioritise strategies and key decision makers—industry, the government and individual horse owners—can now focus the debate regarding user-pays eradication programmes.




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