Prevalence of tick-borne pathogens in questing Ixodes ricinus ticks in urban and suburban areas of Switzerland

Parasit Vectors. 2017 Nov 9;10(1):558. doi: 10.1186/s13071-017-2500-2.

Abstract

Background: Throughout Europe, Ixodes ricinus transmits numerous pathogens. Its widespread distribution is not limited to rural but also includes urbanized areas. To date, comprehensive data on pathogen carrier rates of I. ricinus ticks in urban areas of Switzerland is lacking.

Results: Ixodes ricinus ticks sampled at 18 (sub-) urban collection sites throughout Switzerland showed carrier rates of 0% for tick-borne encephalitis virus, 18.0% for Borrelia burgdorferi (sensu lato), 2.5% for Borrelia miyamotoi, 13.5% for Rickettsia spp., 1.4% for Anaplasma phagocytophilum, 6.2% for "Candidatus Neoehrlichia mikurensis", and 0.8% for Babesia venatorum (Babesia sp., EU1). Site-specific prevalence at collection sites with n > 45 ticks (n = 9) significantly differed for B. burgdorferi (s.l.), Rickettsia spp., and "Ca. N. mikurensis", but were not related to the habitat type. Three hundred fifty eight out of 1078 I. ricinus ticks (33.2%) tested positive for at least one pathogen. Thereof, about 20% (71/358) were carrying two or three different potentially disease-causing agents. Using next generation sequencing, we could detect true pathogens, tick symbionts and organisms of environmental or human origin in ten selected samples.

Conclusions: Our data document the presence of pathogens in the (sub-) urban I. ricinus tick population in Switzerland, with carrier rates as high as those in rural regions. Carriage of multiple pathogens was repeatedly observed, demonstrating the risk of acquiring multiple infections as a consequence of a tick bite.

Keywords: "Candidatus Midichloria mitochondrii"; "Candidatus Neoehrlichia mikurensis"; Anaplasma; Babesia; Borrelia; Ixodes ricinus; NGS; Rickettsia; Tick-borne encephalitis virus; Urban.

MeSH terms

  • Anaplasma phagocytophilum / isolation & purification
  • Anaplasma phagocytophilum / pathogenicity
  • Animals
  • Babesia / genetics
  • Babesia / isolation & purification
  • Babesia / pathogenicity
  • Bacterial Infections / epidemiology
  • Bacterial Infections / transmission
  • Borrelia / genetics
  • Borrelia / isolation & purification
  • Borrelia / pathogenicity
  • Borrelia burgdorferi / genetics
  • Borrelia burgdorferi / isolation & purification
  • Borrelia burgdorferi / pathogenicity
  • Encephalitis Viruses, Tick-Borne / genetics
  • Encephalitis Viruses, Tick-Borne / isolation & purification
  • Encephalitis Viruses, Tick-Borne / pathogenicity
  • Ixodes / microbiology*
  • Ixodes / virology*
  • Prevalence
  • Reverse Transcriptase Polymerase Chain Reaction
  • Rickettsia / genetics
  • Rickettsia / isolation & purification
  • Rickettsia / pathogenicity
  • Suburban Population
  • Switzerland
  • Urbanization
  • Virus Diseases / epidemiology
  • Virus Diseases / transmission