AN AVIAN RESERVOIR (TURDUS-MERULA) OF THE LYME BORRELIOSIS SPIROCHETES

The reservoir competence of passerine birds for the Lyme borreliosis s pirochetes was studied in an enzootic focus in Switzerland. Skin aspir ates and skin biopsies were used to isolate Borrelia spirochetes from Turdus species. B. burgdorferi sensu late was isolated and/or PCR-dete cted in BSK medium containing skin biopsy or skin aspirate from 5 blac kbirds (T. merula) and one song thrush (T. philomelos). Seven isolates were obtained from 3 different blackbirds. Either B. garinii or Borre lia from the genomic group VS116 was found in bird skin samples. Mixed infection occurred in 2 cases. Tick xenodiagnosis was used to determi ne whether blackbirds transmitted Borrelia to ticks. Five xenodiagnose s were performed on 3 different blackbirds. Borrelia DNA was detected in BSK medium inoculated with xenodiagnostic ticks from all the passer ines tested. Isolates cultured from xenodiagnostic ticks were obtained from 2 blackbirds. Isolates belonged to group VS116 (n = 10) and to B . garinii (n = 1). Our study has shown that Turdus sp. are infected by B. garinii and by Borrelia from group VS116 and that blackbirds are i mplicated as reservoirs for these 2 genomic groups of Borrelia, as the y transmit living borreliae to ticks. An association seems to exist be tween birds and Borrelia VS116, and to a lesser extent, B. garinii, si milar to the association existing between small rodents and B. afzelii . Our observations emphasize the fact that different enzootic cycles m aintain Lyme borreliosis spirochetes in nature.