DISTRIBUTION OF BORRELIA-BURGDORFERI SL SPIROCHETE DNA IN BRITISH TICKS (ARGASIDAE AND IXODIDAE) SINCE THE 19TH-CENTURY, ASSESSED BY PCR

The distribution of Borrelia burgdorferi sensu lato, the Lyme borrelio sis agent, was surveyed in British ticks in the collection of the Natu ral History Museum, London. Alcohol-preserved specimens of eight speci es of ticks known to attack humans were studied: Ixodes ricinus, I. he xagonus, I. uriae, I. trianguliceps, Dermacentor reticulatus, Haemaphy salis punctata, Rhipicephalus sanguineus and Argas vespertilionis. The sample comprised all life stages and originated from a wide range of host species, collection dates (1896-1994) and geographical localities in England, Scotland and Wales. Borrelia burgdorferi s. l. DNA, detec ted by a polymerase chain reaction that targeted the outer surface pro tein A gene, was found in all eight species. The overall proportion of PCR-positive specimens ranged from 7.8% for I. hexagonus (mostly from mustelids and hedgehogs) to 98.3% for I. uriae (mostly from seabirds) . Borrelia burgdorferi s. l. DNA was found for the first time in the b at parasite A. vespertilionis (85.3%). The spirochaete is newly record ed in British populations of I. trianguliceps (97.4%, mostly from vole s, mice and shrews), D. rericulatus (12.5% from dog and man) and R. sa nguineus (30% from dogs and human dwellings). Of the four tick species with larvae available for testing, examples of I. ricinus, I. urine a nd A. vespertilionis were PCR positive, as were significantly more nym phs than adults of I. ricinus, I. hexagonus and A. vespertilionis. Ana lyses showed that B. burgdorferi s. l. has been consistently present i n British tick populations since at least 1897. Ticks positive for B. burgdorferi s. E. DNA were collected in all months of the year, throug hout Britain, and were found on a wide range of mammal and bird specie s. PCR positivity does not prove vector or reservoir competence, but t he use of archived material has demonstrated an extensive range of hos t-tick relationships involving B. burgdorferi s.l. in Britain for >100 years.