New Rickettsia spp. are continuously being isolated from ticks around the world, but in most cases their pathogenicity remains to be determined. Some rickettsiae first thought to be nonpathogenic have later been associated with human disease, such as Rickettsia slovaca, Rickettsia helvetica, Rickettsia aeschlimannii and, more recently, the Spanish strain Bar29 (Rickettsia massiliae genogroup), which seems to play a role in the pathogenesis of Mediterranean spotted fever. There are many other rickettsiae that, at least to date, have only been found in ticks, namely (i) genotypes IRS3/IRS4, first isolated in Ixodes ricinus ticks from Slovakia; (ii) genotypes RpA4 and DnS14, DnS28, DnS79, DnS94 (belonging to the R. massiliae genogroup), which were first isolated, respectively, from Rhipicephalus pumilio and Dermacentor nutalli ticks from the former Soviet Union; and more recently (iii) the spotted fever group rickettsiae detected in Dermacentor marginatus ticks collected from vegetation in Jaén and La Rioja (Spain), which are closely related to the genotypes DnS14/DnS28. The pathogenicity of all of these rickettsiae remains uncertain, but since other tick-isolated rickettsiae of previously unknown pathogenicity have been shown to cause human disease, the pathogenic potential of these new rickettsiae deserves specific attention.

This work was supported by the Ministerio de Sanidad y Consumo, Fondo de Investigación Sanitaria (FIS), Red temática de Investigación Cooperativa EBATRAG-G03/057.

2 pages.-- PMID: 15252721 [PubMed].-- Printed version published Aug 2004.

Peer reviewed