TICK-BORNE BORRELIOSES PATHOGEN IDENTIFICATION IN IXODES TICKS (ACARINA, IXODIDAE) COLLECTED IN ST. PETERSBURG AND KALININGRAD BALTIC REGIONS OF RUSSIA

Two isolated Baltic seashore populations of Ixodes ticks were studied as vectors of different Borrelia genospecies in Russia by using darkfi eld microscopy and modified polymerase chain reaction (PCR). In the Ka linigrad region (Kurish Spit. forests near the settlements of Lesnoye and Rybachy), 788 Ixodes ricinus (L.) adults and nymphs were collected by nagging and studied Ip darkfield microscopy during 1995-1996. Ther e were 88 darkfield microscopy positive specimens (11.2%) of which 69 were also analyzed by PCR. Borrelia afzelii tend B. garinii were found individually and together in ticks. In this region, on the Kurish Spi t, 7 patients with tick; borrelioses were observed: 2 in the Russian p art of Spit and 5 in the Lithuanian par?. A significant difference was found between Borrelia prevalence during the spring and fall peaks of tick abundance. Specimens that were darkfield microscopy positive pre vailed in the fall (25.15%) in comparison with the spring peak (7.3%). The number of specimens with identified genospecies prevailed in the spring: 22 out of 35 versus 4 out of 31 in the fall. Among 29 PCR posi tive I. ricinus, 21 contained B. afzelii, 3 had B. garinii, and 2 had dual infection. In 1995, only B. afzelii infected specimens were obser ved. In the vicinity of St. Petersburg (the seashore of;he northern Gu lf of Finland, in forests near Lisy Nos, Morskaja) during 1992-1996, 3 1 patients with a tick-borne borrelioses were registered. We collected 487 Ixodes persulcatus Schulze by flagging and studied them by darkfi eld microscopy in 1995-1096 of which 144 ticks (29.6%) were darkfield microscopy positive. Sixty darkfield-positive specimens mere analyzed by PCR, and in 88.3% of cases genospecies were identified. B. afzelii and B. garinii were identified individually and together in ticks. In 1995, I. persulcatus with dual infection prevailed with 11 out of 21 ( 52.4% positive), whereas in 1996, most I. persulcatus ticks rs contain ed B., gn,garinii (81.2%). Dual infection was observed in 4 of 32 (12. 5%) ticks. Dual infections in I. persulcatus females increased within the seasonal peal; of tick activity as was observed in 1995 auld in 19 96. Many patients not only had erythema migrans, but also exhibited ea rly neurological symptoms that coincided with the number of tick vecto rs that had dual infections in June, indicating that these patients we re bitten by female ticks that had dual infections. A significant diff erence existed between levels of infection in I. ricinus and I. persul catus, with all 3 types of Borrelia infection observed 2 times more of ten in I. persulcatus than in I. ricinus and dual infection occurred i n I. persulcatus 3.7 times more often. It appeared that I. persulcatus is a much more dangerous vector of tick-borne borrelioses than I. ric inus.