PECULIARITIES OF CADMIUM-TOLERANT POPULATIONS OF IXODES TICKS: SPECIFICITY OF THEIR MICROBIOCENOSES, IMMUNITY AND VECTOR CAPACITY

摘要

The appearance and prevalence of exoskeleton anomalies in Ixodes ticks chosen as markers of anthropogenic press allows to reveal their distribution and the rate of occurrence in Russia and several Western European countries. Chemical analyses show theappearance of anomalies as being related to the accumulation of heavy metal ions, first of all cadmium which prevails in specimens and is known as changing tick metabolism. Cdconcentrations are 1.5-2 times higher in anomalous ticks than in normal ones,cadmium supposedly suppressing tick immunity. To provide indirect evidence of this, microflora of anomalous and normal ticks has been compared, with 73 hungry tick females collected in April 2003 and 2004 in a focus of tick-borne diseases near St. Petersburg, Russia screened micro-biologically. A study of "vulgar" microflora in both parts of the Ixodes persulcatus Schulze population shows the whole microbiocenosis of anomalous and normal ticks as being quite different. Microflora of Gram-negative and Gram-positive bacteria, bacilli, cocci and fungi appears to be much richer in anomalous ticks than in normal ones (47 versus 28 species). Only 14 (of 61) species representing the "vulgar" microflora are coincided in both groups of ticks. Not more than 4 species of microorganisms are present per normal tick, whereas one tick with exoskeleton anomalies can contain 5, 6 or even 7 species simultaneously. Only in anomalous ticks do the cocci of the genus Staphylococcus and the fungi of the genus Penicillum absolutely prevail. Staphylococci are known as active stimulants of lysozyme and defensin production, both the main tools of the tick immune system. Scarcity of these cocci and fungi in normal ticks and their abundance in anomalous ones, as well as the great prevalence of multi infections in anomalous ticks are accepted as markers of their immune system suppression. Revised (6,169 adult ticks screened using PCR; 1996-2000) data concerning the prevalence of tick-borne multi infections (such as mixtures of Borrelia, Ehrlichia, Anaplasma, Babesia or tick-borne encephalitis virus) confirm that exoskeleton anomalies represent external markers of cadmium accumulation, increased tick vector capacity and dan-gerousness. Analysis of anomalous tick microflora supports this observation as well, because only among anomalous tick numerous phyto- or zoo-pathogenic bacteria and, especially, fungi have been revealed, which can be very dangerous for man with an immune system suppressed by any factor or associated disease.