Control of Rhipicephalus sanguineus ticks and Rocky Mountain spotted fever informed by an in silico tool

We explored a compartment “susceptible-infected-recovered” model to prioritize and test the effectiveness of dog- and tick-based interventions against Rocky Mountain spotted fever and its tick vector Rhipicephalus sanguineus s.l. In the face of increasingly urban epidemics of RMSF with high case fatality, particularly targeting marginalized communities, wrap-around campaigns (comprising all or some of canine culling, fertility control, and restraint to property; on-dog and environmental acaricide; and education and awareness programs for public health workers and at-risk residents) are unsustainably resource-intensive and may lack efficacy in managing the very hard to control tick. Our model allows us to strategize interventions and develop an optimized campaign against RMSF, using parameters associated with the epidemic in Ensenada, Baja California as an example. Combining usage of acaricides on dogs and the environment optimized success as measured by up to 10 years of no new canine cases, a proxy for human cases, as well as reduced tick burden. Success was greater when the campaign was begun in winter or spring and achieved at least 60 % coverage. This combination was considerably more successful than either dog or environmental acaricide alone, culling of dogs which was only successful with 100 % of dogs removed, and spay/neuter campaigns which did not reduce tick burdens. However, spay/neuter of outside dogs as an adjunct to the acaricide campaign helped stabilize the canine population and encouraged herd immunity. Although parameterized for Ensenada, the model can easily be run for other communities where data on canine tick burden and tick life history traits are available, in order to tailor intervention details such as optimal timing, coverage, and re-application frequency even when public health resources are limited.