The role of host and habitat spatial heterogeneity in the distribution of ticks and tick-borne diseases on Scottish upland moorland

How host and habitat heterogeneity affects the distribution of ticks in the Scottish upland environment was examined, and the prevalence of two important tick-borne diseases in questing, field-collected ticks was investigated.  This data was used to test the predictions of an influential model of louping-ill virus. Both hosts and habitat were found to be important predictors of Ixodes ricinus nymph abundance.  In general, the highest nymph numbers were collected from areas of heather habitat, and lowest numbers from areas of boggy ground.  Nymph numbers increased with increasing red deer density, but were negatively associated with increasing both mountain hare and red grouse density. A total of 1063 field collected, questing ticks were individually tested for louping-ill virus, of which 621 were also tested for Borrelia burgdorferi sensu lato.  Louping-ill RNA was detected in 7.8 % of all ticks tested.  The percentage of ticks positive for louping-ill virus did not vary with tick stage, collection site, month, or vegetation type, and was not correlated with host density of host seroprevalence.  B. burgdorferi was detected in 1.4 % of the ticks.  No simultaneous infections of louping ill virus and Borrelia spp. were detected. Field data on tick abundance and pathogen prevalence collected during this study was used to challenge an influential model of louping-ill virus dynamics.  The model proved relatively successful at predicting tick abundance, but underestimated the extent of louping-ill virus.  The single patch model was adapted to form a two-patch modelling allowing red deer movement between the two patches.  Allowing the movement of deer between two patches with different host densities shifted the threshold for louping-ill virus persistence, allowing its persistence in almost all red deer-grouse-hare scenarios.