Address for correspondence: N.V. Rudakov, Omsk Research Institute of Natural Foci Infections, 644080, prospect Mira, 7 Omsk, Russia.
nicolay{at}rudakov.omsk.su
Ann. N.Y. Acad. Sci. 990: 12-24 (2003).
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 udnerstood. 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.
