This study deals with the ecology of Lyme borreliosis in Europe.
The relationships between Borrelia burgdorferi sensu lato
spirochetes, Clethrionomys and Apodemus rodent reservoirs
and the Ixodes ricinus tick vector were investigated during 16
consecutive months in an enzootic area in Switzerland. Cultivation of ear
skin biopsies was used to isolate spirochetes from
C. glareolus, A. sylvaticus, A. flavicollis
and Glis glis. Borrelia infection was more frequently
observed in Clethrionomys
than in Apodemus. Tick xenodiagnosis was used to determine the
infectivity of rodents. The infection rate in ticks fed on
Clethrionomys was higher than that in ticks fed on Apodemus,
but Apodemus yielded more infected ticks than Clethrionomys
because of a better tick moulting success. Xenodiagnostic ticks were placed
into BSK medium to obtain isolates. Isolates
from rodents and rodent-feeding ticks were all identified as B. afzelii.
The follow-up of the infectivity status of repeatedly
recaptured rodents clearly demonstrated that these hosts remained infective
for ticks during winter till the following spring.
Comparing C. glareolus and A. sylvaticus, each rodent
species showed different host infection, different host infectivity
and contributed differently to the moulting success of feeding ticks. These
factors influence differentially the pattern of
transmission of B. afzelii from Clethrionomys voles and
Apodemus mice to I. ricinus ticks.