USING A VEGETAL INDICATOR TO CARTOGRAPHY THE POPULATIONS OF AN EXOPHILE TICK ON THE SCALE OF A COUNTRY - THE EXAMPLE OF IXODES-RICINUS, A VECTOR OF LYME-BORRELIOSE IN FRANCE

In Western Europe, Ixodes ricinus has been recognized as the vector of several animal and human diseases. The last discovered nosological en tity linked with that species is Lyme Borreliosis, whose repartition i s to date badly known. It then becomes important to have a comprehensi ve view of the vector distribution in order to know what areas are pro pitious to the disease. The tick is an exophile species and lives more particularly in wooded areas. For mapping the species in France, we h ave conceived a method L using the different vegetation types as ecolo gical indicators, each << series >> having homogeneous environmental c onditions. The successive steps in the accomplishment of the study (fr om the zoning of the territory to the tick sampling) are presented her e (Use of small and medium scale vegetation maps, fixing the forest st ations to be prospected, standardization of the flagging technique). S ome results are analysed here in order to give an idea and the limits of the method. In this purpose, the authors point out the results obta ined in two different areas. In South-Western France, the vegetation s eries can be easily distinguished and are largely variable from one ar ea to another. In the present study, the tick frequencies are also pro ved to be varying from one << series >> to an other. In this case, the vegetation can be considered as an efficient indicator. The acarologi cal data are obviously in connection with the ecological variability o f the territory. As regard of Brittany (North-Western, France) because the homogeneity and uniformity of the area, the vegetation series can not be distinguished continuously. So the use of the vegetal indicator from the reason that has been exposed, can be thought of little inter est.