Geographic distribution determinism of tick-borne diseases.

In Europe, the distributions of the two main diseases transmitted by the ti ck l. ricinus (Linne, 1758) differ in their structure and extent. The distr ibution of Lyme borreliosis is widespread and uniform while that of tick-bo rne encephalitis is more restricted and discontinuous. This difference rais es the question of the existence of a determinism for the geographical dist ribution of Vector-home diseases and, more specifically, of the tick-borne diseases. The current explanation for the difference of extension is that t he period of infectivity may Vary in Vertebrate reservoirs. The new hypothe sis is that the discontinuity of the distribution of tick-borne encephaliti s may be due to the local microclimatic conditions allowing or nor the two stages (larvae and nymphae) to be simultaneously present on their hosts. (C ) 2001 Editions scientifiques et medicales Elsevier SAS.