Targeted pre-emptive rabies vaccination strategies in a susceptible domestic dog population with heterogeneous roaming patterns.

Abstract

Australia is free of canine rabies, however northern regions - such as the Northern Peninsula Area (NPA), Queensland - are at risk of an incursion from nearby rabies-infected Indonesian islands. Early detection and reactive vaccination is the current Australian policy to eradicate an incursion. Early detection in this region is challenging, so pre-emptive vaccination might be an effective strategy. The NPA dog population also has a heterogenous contact structure, with three roaming categories previously characterised, which could be exploited in targeted pre-emptive vaccination strategies for more efficient use of limited resources. To evaluate the effectiveness of a pre-emptive vaccination program, an agent-based rabies spread simulation model was used to simulate outbreaks with a range of pre-emptive vaccination coverages. Increasing proportions (10% increments) of the dog population randomly vaccinated were modelled, and at the most efficient random vaccination coverage we then explored 10 pre-emptive vaccination strategies targeting different dog roaming categories (whilst maintaining the same overall population level vaccination coverage). All pre-emptive vaccination strategies were simulated 2000 times without and with a 70% random reactive vaccination strategy, following rabies detection. All random pre-emptive vaccination coverages reduced outbreak size and duration compared to no pre-emptive vaccination. A 40% random coverage was most efficient. Targeted strategies that pre-emptively vaccinated proportionally more roaming dogs were more effective than a random 40% vaccination coverage and strategies that targeted non-roaming dogs. The pre-emptive vaccination strategies that targeted non-roaming dogs produced significantly larger and longer outbreaks. These results suggest that pre-emptive vaccination can reduce potential rabies outbreaks in this region and that such a strategy should not just focus on easily accessible dogs that do not roam often or at all. A cost-benefit analysis is required to determine whether the implementation of such pre-emptive vaccination strategies is also cost-effective, which is essential in the resource-poor communities of this region.