RATE OF TICK-BORNE PATHOGEN PREVALENCE AND A RISK OF MAN MIX - INFECTION IN A RECREATIONAL ZONES OF ST. PETERSBURG MEGAPOLIS

Abstract:
In the recreational zone of St. Petersburg the regular collections of Ixodes persulcatus Schulze ticks were made during 1995-1998 within a tick activity season (April-July). Ticks were collected by flagging and their infection rates were estimated using darkfield microscopy for spirochetes, IFA methods for Borrelia and tick-borne encephalitis virus (TBEV) determination and PCR - for Borrelia and Ehrlichia species identification. The total number of the used ticks - 1,559. Spirochete prevalence oscillated between 26-36% during different seasons, near 80% of them were identified as Borrelia garinii or Borrelia afzelii. TBEV antigen contained 0.7-1.2% of specimens. The most epidemiologically important fact consists in the discover that mixt-infection is very typical for I. persulcatus vectors. 50% of TBEV infected specimens contained spirochetes; one among them contained virus, B. afzelii and B. garinii (neuroborrelioses agent) also. From 12.5 to 52% of Borrelia infected ticks contained B. garinii and B. afzelii. Most of dual infected ticks appeared in the middle of the vector seasonal activity period. Mixtinfected patients were bitten also within the middle or the second half of the season. Eight per cent of spirochete infected ticks contained at the same time Ehrlichia sp. There were dual infected specimens which contained B. garinii and Ehrlichia sp. Triple infected specimen, which contained both pathogenic Borrelia species (B. garinii and B. afzelii) and Ehrlichia sp. were discovered. All mentioned above facts strongly suggest that the risk of dual and even triple infection of man in the St. Petersburg vicinity is very probable and high enough.