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

ABSTRACT

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.