Mj. Hubbard et al., DISTRIBUTION OF BORRELIA-BURGDORFERI SL SPIROCHETE DNA IN BRITISH TICKS (ARGASIDAE AND IXODIDAE) SINCE THE 19TH-CENTURY, ASSESSED BY PCR, Medical and veterinary entomology, 12(1), 1998, pp. 89-97
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.