Parasite-mediated apparent competition occurs when one species affects another 
through the action of a shared parasite. One way of controlling the parasite in 
the more susceptible host is to manage the reservoir host. Culling can cause 
issues in terms of ethics and biodiversity impacts, therefore we ask: can 
treating, as compared to culling, a wildlife host protect a target species from 
the shared parasite? We used Susceptible Infected Recovered (SIR) models 
parameterized for the tick-borne louping ill virus (LIV) system. Deer are the 
key hosts of the vector (Ixodes ricinus) that transmits LIV to red grouse 
Lagopus lagopus scoticus, causing high mortality. The model was run under 
scenarios of varying acaricide efficacy and deer densities. The model predicted 
that treating deer can increase grouse density through controlling ticks and 
LIV, if acaricide efficacies are high and deer densities low. Comparing deer 
treated with 70% acaricide efficacy with a 70% cull rate suggested that 
treatment may be more effective than culling if initial deer densities are high. 
Our results will help inform tick control policies, optimize the targeting of 
control methods and identify conditions where host management is most likely to 
succeed. Our approach is applicable to other host-vector-pathogen systems.