Investigation of ecological and environmental determinants for the presence of questing Ixodes ricinus (Acari: Ixodidae) on Gower, South Wales.

The spatial heterogeneity of questing Ixodes ricinus (L.) (Acari: Ixodidae) within endemic areas in Great Britain is well established. Their presence is acutely responsive to blood host availability and their ability to maintain water balance, which are in turn governed by a variety of ecological and environmental factors. This article details the findings of a 3-yr study on the Gower peninsula, south Wales, which investigated the contribution of such factors (both ground- and geographic information systems [GIS] -derived) for predicting the presence of questing I. ricinus (Q(P)), at a local scale. Statistically significant univariate associations were found between Q(P) and calcareous/ neutral grassland and heathland habitats, particularly those grazed by livestock, and various factors that intuitively promote tick survival. For example, topographical features, such as certain aspects, that reduce exposure to cold northerly winds and the hot midday sun, favored Q(P). Similarly, positive associations were found with substrata composed of less permeable soil types and less permeable superficial/bedrock geologies that promote a moist microhabitat and reduce the likelihood of desiccation. Q(P) was also higher in areas of high soil moisture. This study highlighted a number of GIS-derived data sets that could be applied in the development of local and national predictive maps for I. ricinus in Great Britain. An understanding of the influence of these factors on questing I. ricinus can aid targeted tick control programs and help to educate the public, and those occupationally exposed, in understanding likely I. ricinus prolific areas within an I. ricinus endemic region.

Analysis of climatic predictions for extrinsic incubation of Dirofilaria in the United kingdom.

Transmission of dirofilariasis in Europe is dependent upon the presence of sufficient numbers of infected dogs, susceptible mosquitoes, and a suitable climate to permit extrinsic incubation of Dirofilaria in the mosquito intermediate host. Dogs returning to the United Kingdom from overseas have been infected with several vector-borne infections (Babesia, Ehrlichia, Leishmania, and Dirofilaria), and this paper assesses the climatic constraints on the potential rate of extrinsic incubation of Dirofilaria in the United Kingdom. A model using an established algorithm based on accumulated temperature predicts that summer temperatures during 1995-2000 may have been sufficient to permit complete incubation of Dirofilaria in 2 of the years for large parts of southern/central England, and 5 years around London. The occurrence of autochthonous transmission would be dependent upon additional factors related to frequency of returning infected dogs and the distribution and abundance of putative mosquito vectors, and these should be studied further.