In Britain, grey squirrels (Sciurus curolinensis Gmelin) and pheasants (Phasianus colchicus Linnaeus) are important hosts of larvae and nymphs of Ixodes ricinus L., the principal F.uropean vector of the Lyme disease spirochaete, Borrelia burgdorferi sensu lalo, T о test whether squirrels are competent hosts of B. burgdorferi s. I., three females were trapped in the wild and then held in captivity. Following treatment, each animal was exposed to uninfected xenodiagnostic I. ricinus ticks. Squirrel A (an adult) which was inoculated experimentally with B. burgdorferi s.l., transmitted the infection to xenodiagnostic ticks. In contrast, squirrel В (a juvenile that was not inoculated)-showed no evidence of infection. Xenodiagnostic ticks that fed on control squirrel С (an adult) became infected and subsequently transmitted the infection experimentally to an uninfected hamster. The results indicated that squirrel С had a disseminated infection acquired in the wild and which persisted for at least 11 weeks. These data clearly demonstrate that grey squirrels are amplifying and reservoir hosts of B. burgdorferi s.l. The strain associated with squirrels was related to the B. afzelii genotype. Two observations implicated pheasants in a similar role; (i) a high prevalence of infection in engorged larvae collected from trapped pheasants, and (ii) the detection of B. burgdorferi s.l. (В. garinii genotype) in the wattle of 1/10 pheasants using PCR. Xenodiagnostic experiments similar to those undertaken with the squirrels are needed to confirm the role of pheasants in the transmission cycle of Lyme disease spirochaetes.
The European hedgehog, Erinaceus europaeus Linnaeus, 1758, is a common host of Ixodes ricinus L. and I. hexago-nus Leach, vectors of the Lyme disease spirochaete, Borrelia burgdorferi sensu iato. To investigate whether hedgehogs are reservoirs for li- burgdorferi, hedgehogs were captured in a suburban area suitable for both tick species and in an urban area where /. ricinus is absent. The infection status of the hedgehogs was determined by xenodiagnosis using I. ricinus and I. hexagonus larvae. /. hexagonus and/or I. ricinus were found on all hedgehogs (n = 8) from the suburban area. In contrast, only I. hexagonus was infesting animals (n = 5) from the urban area. A total of 12/13 hedgehogs harboured B. burgdorferi infected ticks. Xeno-diagnostic I. ricinus and I. hexagonus larvae that fed on hedgehogs became infected. The results clearly show that European hedgehogs are reservoir hosts of the Lyme disease spirochetes. DNA of B. burgdorferi sensu stricto, В. garinii and В. afzelii was detected in culture from ear biopsy and needle aspiration material and characterized by using a genospecies-specific PCR assay. One hedgehog presented a mixed infection of the skin with fi. burgdorferi sensu stricto and fi. garinii. This study also identifies an enzootic transmission cycle in an urban area involving E europaeus and /. hexagonus. The close association of /. hexagonus with the burrows of its hosts mean that the risks of contact between /. hexagonus and humans may be low.