High prevalence of Borrelia burgdorferi s.l. in the European red squirrel Sciurus vulgaris in France.

The European red squirrel (Sciurus vulgaris) has long been suspected to be a reservoir host of the agents of Lyme borreliosis, in particular B. burgdorferi sensu stricto (s.s.). However, very few data support this hypothesis. Hereafter, we investigated the infections with B. burgdorferi genospecies in road-killed red squirrels collected across France. We also characterized the diversity of hard tick species collected from a subsample of hosts. DNA of B. burgdorferi genospecies were detected and identified from PCR products in ear biopsies using reverse line blot hybridization. Variation in prevalence was investigated accord-ing to biogeographic areas (Mediterranean, Atlantic, Continental, and Alpine), season, sex, relative age, and body mass from 273 squirrels collected 2003­2010. Among the 746 identified tick specimens, no adult was observed, 63% were nymphs, and 37% were larvae all belonging to the species Ixodes ricinus except one nymph identified as I. trianguliceps. Overall, no squirrels of Mediterranean origin and no unweaned juveniles were found infested by hard ticks. Only season explained variation in I. ricinus abundance on squirrels, with more ticks present in spring to summer than in autumn to winter. Squirrels of Mediterranean origin (n = 20) were not found infected with B. burgdorferi sensu-lato (s.l.), which is almost certainly related to the low occurrence of I. ricinus in this region. Based on individuals analyzed in the other regions of France, 11.5% (n = 26) unweaned young harboured B. burgdorferi s.l., which indicates that infection occurred already in the nest. In adults (n = 227), the prevalence of infection with B. burgdorferi s.l. was 27.3%, with 18.9% B. burgdorferi s.s., 11.9% B. afzelii, and 3.5% B. garinii. The season and the body mass, sex, and geographic origin of adults had no effect on the frequency of infection. Infection prevalence of S. vulgaris is among the highest found in rodents in Europe, particularly for B. burgdorferi s.s. supporting the hypothesis that sciurids are particularly suitable hosts for this genospecies.

Macroparasite community of the Eurasian red squirrel (Sciurus vulgaris): poor species richness and diversity.

The Eurasian red squirrel (Sciurus vulgaris) is the only naturally occurring tree squirrel throughout its range. We aim at improving current knowledge on its macroparasite fauna, expecting that it will have a poor parasite diversity because in species that have no sympatric congeners parasite richness should be lower than in hosts sharing their range with several closely related species, where host-switching events and lateral transmission are promoted. We examined gastro-intestinal helminth and ectoparasite communities (excluding mites) of, respectively, 147 and 311 red squirrel roadkills collected in four biogeographic regions in Italy and France. As expected, the macroparasite fauna was poor: we found five species of nematodes and some unidentified cestodes, three fleas, two sucking lice and two hard ticks. The helminth community was dominated by a single species, the oxyurid Trypanoxyuris (Rodentoxyuris) sciuri (prevalence, 87%; mean abundance, 373 ± 65 worms/host). Its abundance varied among seasons and biogeographic regions and increased with body mass in male hosts while decreased in females. The most prevalent ectoparasites were the flea Ceratophyllus (Monopsyllus) sciurorum (28%), whose presence was affected by season, and the generalist tick Ixodes (Ixodes) ricinus that was found only in France (34%). All the other helminths and arthropod species were rare, with prevalence below 10%. However, the first record of Strongyloides robustus, a common nematode of North American Eastern grey squirrels (S. carolinensis), in two red squirrels living in areas where this alien species co-inhabits, deserves further attention, since low parasite richness could result in native red squirrels being particularly vulnerable to parasite spillover.