Seasonal Prevalence of Lyme Disease Spirochetes in a Heterothermic Mammal, the Edible Dormouse (Glis glis)

In Europe, dormice serve as competent reservoir hosts for particular genospecies of the tick-borne agent of Lyme disease (LD) and seem to support them more efficiently than do mice or voles. The longevity of edible dormice (Glis glis) and their attractiveness for ticks may result in a predominance of LD spirochetes in ticks questing in dormouse habitats. To investigate the role of edible dormice in the transmission cycle of LD spirochetes, we sampled skin tissue from the ear pinnae of dormice inhabiting five different study sites in south western Germany. Of 501 edible dormice, 12.6% harbored DNA of LD spirochetes. Edible dormice were infected most frequently with the pathogenic LD spirochete Borrelia afzelii. The DNA of B. garinii and B. bavariensis was detected in ca. 0.5% of the examined individuals. No spirochetal DNA was detectable in the skin of edible dormice until July, 6 weeks after they generally start to emerge from their obligate hibernation. Thereafter, the prevalence of spirochetal DNA in edible dormice increased during the remaining period of their 4 to 5 months of activity, reaching nearly 40% in September. Males were more than four times more likely to harbor LD spirochetes than females, and yearlings were almost twice more likely to be infected than adults. The seasonality of the prevalence of LD spirochetes in edible dormice was pronounced and may affect their role as a reservoir host in respect to other hosts.