Evaluation of factors influencing tick bites and tick-borne infections: a longitudinal study

Bo Bødker Jensen*, Mie Topholm Bruun, Per Moestrup Jensen, Andreas Kristian Pedersen, Pierre Edouard Fournier, Sigurdur Skarphedinsson, Ming Chen

*Corresponding author for this work

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Background: Various tick-borne infections like borreliosis and rickettsiosis pose a health risk to humans in many parts of the world. We investigated seroprevalence of and seroconversion to Borrelia burgdorferi and Rickettsia spp. and relation to tick-bites, weather and clinical manifestations in Denmark. Methods: Blood donors were enrolled at the Hospital of Southern Jutland in June–July with follow-up November–February of 2018 and 2019. Blood samples were collected, and a questionnaire regarding tick bites, potential exposures and symptoms was completed at each visit. Samples were tested for presence of IgM and IgG antibodies directed against B. burgdorferi and Rickettsia spp. using R. helvetica and R. felis as antigens. Data were examined for correlation between tick bites, serological results, potential exposures and symptoms. Results: Two-hundred and fourteen (93 follow-ups) and 130 (38 follow-ups) blood donors were included in 2018 and 2019, respectively. The total borrelia seroconversion rate was 6.3% (CI 2.1–10.5), while the prevalence of IgM and IgG antibodies was 7.8% (CI 4.9–10.6) and 6.7% (CI 4–9.3), respectively. Seroconversion to Rickettsia spp. was detected in one participant. Tick bites and seroconversion were not significantly associated with the reported unspecific symptoms, but unspecific symptoms were common in the study population. There was no significant difference in number of tick bites or seroconversion/prevalence between seasons with highly alternating weather. Conclusions: Results suggest that weather conditions in an individual year have a limited impact. Anti-Borrelia-antibodies do not seem to persist in serum for several years. Rickettsiosis is of limited concern in Denmark. Graphic abstract: [Figure not available: see fulltext.]

Original languageEnglish
Article number289
JournalParasites and Vectors
Number of pages9
Publication statusPublished - 29. May 2021

Bibliographical note

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© 2021, The Author(s).


  • Borreliosis
  • Climate
  • Prevalence
  • Rickettsiosis
  • Seroconversion
  • Symptoms
  • Tick
  • Tick-borne infections


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