title: Larvae of Ixodes ricinus transmit Borrelia afzelii and B. miyamotoi to vertebrate hosts.
abstract: BACKGROUND
  Lyme borreliosis is the most common tick-borne human disease and is caused by Borrelia burgdorferi sensu lato (s.l.). Borrelia miyamotoi, a relapsing fever spirochaete, is transmitted transovarially, whereas this has not been shown for B. burgdorferi (s.l). Therefore, B. burgdorferi (s.l) is considered to cycle from nymphs to larvae through vertebrates. Larvae of Ixodes ricinus are occasionally B. burgdorferi (s.l) infected, but their vector competence has never been studied.
  
  
  METHODS
  We challenged 20 laboratory mice with field-collected larvae of I. ricinus. A subset of these larvae was analysed for infections with B. burgdorferi (s.l) and B. miyamotoi. After three to four challenges, mice were sacrificed and skin and spleen samples were analysed for infection by PCR and culture.
  
  
  RESULTS
  Field-collected larvae were naturally infected with B. burgdorferi (s.l) (0.62%) and B. miyamotoi (2.0%). Two mice acquired a B. afzelii infection and four mice acquired a B. miyamotoi infection during the larval challenges.
  
  
  CONCLUSIONS
  We showed that larvae of I. ricinus transmit B. afzelii and B. miyamotoi to rodents and calculated that rodents have a considerable chance of acquiring infections from larvae compared to nymphs. As a result, B. afzelii can cycle between larvae through rodents. Our findings further imply that larval bites on humans, which easily go unnoticed, can cause Lyme borreliosis and Borrelia miyamotoi disease.
authors.affiliation: Laboratory of Entomology, Wageningen University, PO box 16, 6700, AA, Wageningen, The Netherlands. gilian.vanduijvendijk@wur.nl.
authors.forename: Gilian
authors.initials: G
authors.lastname: van Duijvendijk
authors.affiliation: Laboratory for Zoonosis and Environmental Microbiology, National Institute for Public Health and Environment (RIVM), Bilthoven, The Netherlands. elena.coipan@wur.nl.
authors.forename: Claudia
authors.initials: C
authors.lastname: Coipan
authors.affiliation: Center for Experimental and Molecular Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands. a.wagemakers@amc.uva.nl.
authors.forename: Alex
authors.initials: A
authors.lastname: Wagemakers
authors.affiliation: Laboratory for Zoonosis and Environmental Microbiology, National Institute for Public Health and Environment (RIVM), Bilthoven, The Netherlands. manoj.fonville@rivm.nl.
authors.forename: Manoj
authors.initials: M
authors.lastname: Fonville
authors.affiliation: Center for Experimental and Molecular Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands. j.i.ersoz@amc.uva.nl.
authors.forename: Jasmin
authors.initials: J
authors.lastname: Ersöz
authors.affiliation: Department of Medical Microbiology, Academic Medical Center, University of Amsterdam, Center for Experimental and Molecular Medicine, Amsterdam, The Netherlands. g.a.oei@amc.uva.nl.
authors.forename: Anneke
authors.initials: A
authors.lastname: Oei
authors.affiliation: Department of Parasitology and Zoology, Faculty of Veterinary Science, SzentIstvan University, Budapest, Hungary. FoldvariGabor@gmx.de.
authors.forename: Gábor
authors.initials: G
authors.lastname: Földvári
authors.affiliation: Center for Experimental and Molecular Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands. j.w.hovius@amc.uva.nl.
authors.forename: Joppe
authors.initials: J
authors.lastname: Hovius
authors.affiliation: Laboratory of Entomology, Wageningen University, PO box 16, 6700, AA, Wageningen, The Netherlands. willem.takken@wur.nl.
authors.forename: Willem
authors.initials: W
authors.lastname: Takken
authors.affiliation: Laboratory for Zoonosis and Environmental Microbiology, National Institute for Public Health and Environment (RIVM), Bilthoven, The Netherlands. hein.sprong@rivm.nl.
authors.forename: Hein
authors.initials: H
authors.lastname: Sprong
mesh_terms: D000818:Animals; D001898:Borrelia / Q000302:isolation & purification*; D004195:Disease Models, Animal; D018562:Disease Transmission, Infectious; D018884:Ixodes / Q000382:microbiology*; D007814:Larva / Q000382:microbiology; D008193:Lyme Disease / Q000635:transmission*; D051379:Mice; D012867:Skin / Q000382:microbiology; D013154:Spleen / Q000382:microbiology