Ecology and Epidemiology of Spotted Fever Group Rickettsiae and New Data from Their Study in Russia and Kazakhstan

Abstract

Rickettsiae represent a wide range of pathogenicity from classic and new pathogens to endosymbionts of eukaryotic cells. Recent studies of rickettsiae have widened the number of representatives of genus Rickettsia, especially in the spotted fever group (SFG). Rickettsiae of SFG are tick-borne microorganisms with effective transovarial and transstadial transmission. The main hosts are ticks (Dermacentor, Rhipicephalus, Haemophysalis, Ixodes, and Amlyomma). Strategy of maintenance of tick microorganisms is vector-type transfer and tropism to endothelial cells or blood cells of animals. The main epidemiological characteristics of SFG rickettsioses are different kinds of anthropogenic activity and connection of morbidity with seasonal tick activity. Two other important characteristics are quantitative and qualitative heterogeneity of its populations (different genotypes of Rickettsia in the same territory and species of ticks, for example) and coexistence of different tick microorganisms (rickettsiae, borreliae, ehrlichiae, tick-borne encephalitis complex viruses, etc.). The role of new rickettsial genotypes in infectious diseases is poorly understood. Simultaneous study of ticks after bites, blood and skin biopsies of patients may be used for detection of spectrum of tick-borne pathogens in mixed natural foci. Interference between rickettsiae with different virulence may affect its populations and levels of morbidity.

Rickettsiae of the spotted-fever group in ixodid ticks from Hungary: identification of a new genotype ('<I>Candidatus</I> Rickettsia kotlanii')

“…The 16S-rDNA and gltA amplicons from four of the positive pools were identical with the (Psaroulaki et al, 2003(Psaroulaki et al, , 2005Rudakov et al, 2003;Sanogo et al, 2003;Fournier et al, 2005;Merino et al, 2005;Parola et al, 2005b;Sréter-Lancz et al, 2005; present study).…”

Potential effects of mixed infections in ticks on transmission dynamics of pathogens: comparative analysis of published records

“…Ticks coinfected with both rickettsiae vertically transmit only the nonpathogenic species, which influences the distribution of R. rickettsii. Similar negative interactions apparently occur among other arthropod-transmitted rickettsiae (Macaluso et al 2002;Rudakov et al 2003). De la Fuente et al (2002) inoculated I. scapularis cells with different strains of Anaplasma marginale, and found that only one strain persisted.…”

Spotted Fever: Epidemiology and Vector-Rickettsia-Host Relationship in Rio de Janeiro State

“…Different species of the Spotted-Fever Group of Rickettsia (SFGR) are considered etiologic agents of spotted fever (SF), a zoonosis widely distributed throughout the world, with seasonal and sporadic outbreaks that may involve high mortality rates (Raoult and Roux, 1997; Rudakov et al, 2003; Parola et al, 2009, 2013; Eremeeva and Dasch, 2015). …”