[Evolution of populations of ticks (Ixodidae and Argasidae) in relation to artificialization of the environment in the French Alps. Epidemiologic effects].

The results presented in this study are based on observations made during some 10 years in the French Alps and their surroundings. Forest clusters, as they still cover comparatively large areas, are considered the most favorable foci for several Ixodid species. Recent studies, however, have shown that environment modified by man also harbours large populations of ticks. The spreading of certain species around and even into cities is actually taking place. The following categories of tick species may be distinguished with reference to the artificialization process of the environment: 1. species occurring mainly in forest areas (Ixodes ricinus, I. trianguliceps); 2. species occurring in agricultural, suburban and preurban areas (Dermacentor reticulatus, Rhipicephalus turanicus); 3. species found in either natural wholes, burrows etc. or in constructions amidst rural areas (I. hexagonus, I. canisurga, R. pusillus); 4. species present exclusively in buildings, in either rural or urban areas (R. sanguineus, Argas reflexus). The vectorial role of the various tick species is discussed with regard to the artificialisation process. Particular attention is drawn to the appearance of new, and the extension of previously known foci of disease transmission in the vicinity of large cities.