Lyme Borreliosis is the most common tick-transmitted disease in North America and Europe. Borrelia burgdorferi sensu lato causes Lyme disease and is transmitted by a tick belonging to Ixodes genus. The risk of tick-borne infection depends on the ecology of ticks. The risk of human infection depends on the density of the tick population and its infection rate. The aim of this manuscript is to review the ecology of Ixodes ricinus the main vector of Lyme disease in Western Europe, the reservoir hosts, and studies on locations of Ixodes and Borrelia in France. Ixodes ricinus is widely distributed over the French territory except in Mediterranean areas and land above than 1,500 m.