Seasonal variations in detecting Borrelia burgdorferi sensu lato in rodents from north eastern Austria.

Austria is well known as an endemic area of Lyme borreliosis. To assess the annual variation of rodent populations that may host agents of Lyme borreliosis we collected rodents in northeastern Austria. Life traps were set out every six weeks during a year consecutively in one each of the three different zones (Hohenau, Ernstbrunn, Vienna Woods) that cover the main habitat characteristics of small mammals in northeastern Austria. Rodents were collected and identified. Samples of heart, urine bladder and brain were removed under aseptic conditions for cultivation of borrelia. Samples of heart muscle were additionally used for molecular detection of borrelia by Real-Time polymerase chain reaction. PCR was performed with borrelia universal primers and with species-specific primers. 938 mice were caught, most frequently Apodemus flavicollis (44%), followed by Clethrionomys glareolus (35%), Microtus arvalis (9%), A. sylvaticus (7%) and Mus musculus (6%). Significant differences were seen in the total number of catch per area (Hohenau, Ernstbrunn, Vienna Woods equal 10:9:2) and in the distribution of the various rodent species in the respective areas. Borrelia strains were grown from only 65 (7%) animals, and more frequently isolated from bladder wall than from heart muscle, and only once from brain. Heart specimens of 223 animals were positive by borrelia PCR (24%), most frequently of the rodent species A. flavicollis (43%) and C. glareolus (38%). Borrelia afzelii was most frequently identified, followed by B. burgdorferi sensu stricto, B. garinii and by mixed infection of B. afzelii with B. burgdorferi sensu stricto. B. garinii was most frequently detected in heart samples of A. sylvaticus (about 20%). In about 3% of PCR positive samples the identification of one of the three mentioned genospecies of borrelia could not be ascertained with the test panel used. The results confirm the rodent species A. flavicollis, A. sylvaticus, M. arvalis and C. glareolus as reservoir animals for B. afzelii, B. garinii and B. burgdorferi sensu stricto, agents of Lyme borreliosis. Notable is the salient presence of B. garinii in heart specimens of A. sylvaticus.