Bridging of cryptic Borrelia cycles in European songbirds.
The principal European vector for Borrelia burgdorferi s.l., the causative agents of Lyme disease, is the host-generalist tick Ixodes ricinus. Almost all terrestrial host-specialist ticks have been supposed not to contribute to the terrestrial Borrelia transmission cycles. Through an experiment with blackbirds, we show successful transmission by the widespread I. frontalis, an abundant bird-specialized tick that infests a broad range of songbirds. In the first phase of the experiment, we obtained Borrelia-infected I. frontalis (infection rate: 19%) and I. ricinus (17%) nymphs by exposing larvae to wild blackbirds that carried several genospecies (Borrelia turdi, B. valaisiana, B. burgdorferi s.s.). In the second phase, pathogen-free blackbirds were exposed to these infected nymphs. Both tick species were able to infect the birds, as indicated by the analysis of xenodiagnostic I. ricinus larvae which provided evidence for both co-feeding and systemic transmission (infection rates: 10%-60%). Ixodes frontalis was shown to transmit B. turdi spirochetes, while I. ricinus transmitted both B. turdi and B. valaisiana. Neither species transmitted B. burgdorferi s.s. European enzootic cycles of Borrelia between songbirds and their ornithophilic ticks do exist, with I. ricinus potentially acting as a bridging vector towards mammals, including man.
Evolutionary Ecology Group, Department of Biology, University of Antwerp, Antwerp, Belgium.
Dieter
D
Heylen
Laboratory for Zoonoses and Environmental Microbiology, National Institute for Public Health and Environment (RIVM), Bilthoven, the Netherlands.
Aleksandra
A
Krawczyk
Center for Vector and Infectious Diseases Research, National Institute of Health Doutor Ricardo Jorge, Lisbon, Portugal.
Isabel
I
Lopes de Carvalho
Center for Vector and Infectious Diseases Research, National Institute of Health Doutor Ricardo Jorge, Lisbon, Portugal.
Maria Sofia
MS
Núncio
Laboratory for Zoonoses and Environmental Microbiology, National Institute for Public Health and Environment (RIVM), Bilthoven, the Netherlands.
Hein
H
Sprong
Center for Vector and Infectious Diseases Research, National Institute of Health Doutor Ricardo Jorge, Lisbon, Portugal.|MARE - Marine and Environmental Sciences Centre, Department of Life Sciences, University of Coimbra, Coimbra, Portugal.
Ana Cláudia
0000-0001-7833-4463
AC
Norte
D000818:Animals; D001715:Bird Diseases / Q000382:microbiology / Q000635:transmission*; D025065:Borrelia burgdorferi / Q000235:genetics / Q000254:growth & development* / Q000302:isolation & purification; D005060:Europe; D007303:Insect Vectors / Q000382:microbiology*; D018884:Ixodes / Q000382:microbiology*; D007814:Larva / Q000254:growth & development; D008193:Lyme Disease / Q000382:microbiology / Q000635:transmission*; D020308:Songbirds / Q000382:microbiology*