Rickettsioses

1 - INTRODUCTION

Rickettsiae are strictly intracellular, rod-shaped organisms belonging to the order Rickettsiales and the alpha-1 Proteobacteria subgroup [1]. Recent advances in molecular biology have led to changes being made to their taxonomy. Thus, Coxiella burnetii and Bartonella spp. are no longer part of the Rickettsiales order. This order currently comprises bacteria of the Rickettsiaceae family including the genus Rickettsia (rickettsiae from the spotted fever and typhus groups) and the genus Orientia, and bacteria of the Anaplasmataceae family including the genera Ehrlichia, Anaplasma, Neorickettsia and Wolbachia. All these bacteria are responsible for rickettsioses, mostly transmitted to humans by arthropods. To date, more than twenty pathogenic species of rickettsiae have been identified worldwide. The clinical manifestations of rickettsioses are due to specific tropism of the bacteria for endothelial cells, which leads to inflammation of small- and medium-sized blood vessels. These diseases often include cutaneous symptoms which explains the need for dermatologists to know about them. Furthermore, some rickettsioses are currently considered as emerging diseases throughout the world and particularly in Europe.