ACAROLOGICAL DATA FOR THE ECO-EPIDEMIOLOG IC STUDY OF LYME-BORRELIOSIS - IXODES-RICINUS LINNE, 1758 - POPULATIONS IN SOUTH WESTERN FRANCE

In Order to understand how Lyme Borreliosis foci are generated on the French territory, a complete picture of the true distribution of the t ick vector Ixodes ricinus is required. A set of fundamental data was a cquired through a method using plant communities as indicators. The re sults presented in this article are related to the South-Western quadr ant of France. The study area includes the following regions : Landes, Bassin Aquitain, the foot-hills of the Pyrenees and the western part of Massif Central. The aim of the study was to ascertain the presence of the vector in the various parts of a territory of great ecological variety. A zoning was first carried out in order to define phyto-ecolo gical and geographical units. Seventeen units were delineated. In a ra nge of 5 to 10 forest experimental sites per unit, the flagging method was used for one hour's time to take samples of the tick during its p eriod of activity. Ixodes ricinus was found in all the phytoecological zones, except three. Its occurrence frequency ranges from 0 % to 80 % . The Atlantic influence is quite propitious to the species, whereas t he Mediterranean climate is not. The supramediterranean series of Quer cus pubescens is not convenient for the species. The presence of Ixode s ricinus was ascertained at numerous sites in forests belonging to th e Atlantic series of Quercus pedunculata as well as in the artificial pine forest of Pinus maritimus. Dermacentor reticulatus is the other t ick species the most frequently encountered in the same forests as Ixo des ricinus in the study area.