Scrub typhus

Bacteria of the genus Rickettsia are obligate intracellular rods that retained basic fuchsin when stained by the method of Gimenez. This genus has long been used as a generic term of small intracellular bacteria. However, taxonomic progress made over the last years has deeply modified the definition of “rickettsia”. As a result, in 1995 the position of R. tsutsugamushi has reclassified from the genus Rickettsia into a separate new genus, Orientia (Tamura et al. 1995).Scrub typhus, also known as ‘tsutsugamushi fever’, occurs only in Asia and is a chigger-borne zoonosis. The disease is acute, febrile, potentially fatal and has been known for centuries in China where it was probably described as early as in the fourth century BC (Parola and Raoult 2006). These last years this infection has been re-emerging because of descriptions of strains of O. tsutsugamushi with reduced susceptibility to antibiotics and of the surprising interactions between scrub typhus and the human immunodeficiency virus (HIV). It is estimated that more than a million cases of scrub typhus are transmitted annually in Asia and more than a billion people are at risk (Rosenberg 1997).