A prospective study on the incidence of Borrelia burgdorferi sensu lato infection after a tick bite in Sweden and on the Åland Islands, Finland (2008-2009).
Lyme borreliosis (LB) is a common and increasing tick-borne disease in Europe. The risk of acquiring a Borrelia infection after a tick bite is not fully known. Therefore, we investigated the incidence of Borrelia infection after a bite by a Borrelia-infected tick and if the Borrelia load and/or the duration of tick-feeding influenced the risk of infection. During 2008-2009, ticks and blood samples were collected from 1546 tick-bitten persons from Sweden and the Åland Islands, Finland. Follow-up blood samples were taken 3 months after the tick bite. The duration of tick feeding was microscopically estimated and Borrelia was detected and quantified in ticks by real-time PCR. Anti-Borrelia antibodies were detected in sera using ELISA tests and immunoblot. Five percent (78/1546) of the study participants developed Borrelia infection (LB diagnosis and/or seroconversion) after a tick bite (45% bitten by Borrelia-infected ticks and 55% bitten by uninfected ticks). Of these, 33 developed LB (whereof 9 also seroconverted) while 45 participants seroconverted only. Experience of non-specific symptoms was more frequently reported by Borrelia-infected participants compared to uninfected participants. All who seroconverted removed "their" ticks significantly later than those who did not. The Borrelia load in the ticks did not explain the risk of seroconversion. Regional and sex differences in the Borrelia seroprevalence were found. The risk of developing a Borrelia infection after a bite by a Borrelia-infected tick is small but increases with the duration of tick feeding.
Medical Microbiology, Department of Clinical and Experimental Medicine, Linköping University, 581 85 Linköping, Sweden.
Peter
P
Wilhelmsson
Infectious Diseases, Department of Clinical and Experimental Medicine, Linköping University, 581 85 Linköping, Sweden; Clinical Immunology, Department of Clinical and Experimental Medicine, Linköping University, 581 85 Linköping, Sweden. Electronic address: linda.fryland@liu.se.
Linda
L
Fryland
Medical Microbiology, Department of Clinical and Experimental Medicine, Linköping University, 581 85 Linköping, Sweden.
Pontus
P
Lindblom
Department of Infectious Diseases and Department of Clinical and Experimental Medicine, Linköping University, 581 85 Linköping, Sweden.
Johanna
J
Sjöwall
Division of Infectious Diseases, Department of Clinical Microbiology, Umeå University, 901 85 Umeå, Sweden.
Clas
C
Ahlm
School of Health Science, Blekinge Institute of Technology, 371 79 Karlskrona, Sweden.
Johan
J
Berglund
Department of Infectious Diseases, Kalmar County Hospital, 381 95 Kalmar, Sweden.
Mats
M
Haglund
Department of Clinical Microbiology, Division of Medical Services, Ryhov County Hospital, 551 85 Jönkoping, Sweden.
Anna J
AJ
Henningsson
Department of Communicable Disease Control and Prevention, Region Västra Götaland, Skaraborg Hospital, 541 85 Skövde, Sweden.
Peter
P
Nolskog
The Åland Group for Borrelia Research, Mariehamn, Åland, Finland.
Marika
M
Nordberg
The Åland Group for Borrelia Research, Mariehamn, Åland, Finland.
Clara
C
Nyberg
Department of Internal Medicine, Hässleholm Hospital, 281 38 Hässleholm, Sweden; Department of Clinical Sciences, Lund University, 221 00 Lund, Sweden.
Katharina
K
Ornstein
The Åland Group for Borrelia Research, Mariehamn, Åland, Finland.
Dag
D
Nyman
Clinical Immunology, Department of Clinical and Experimental Medicine, Linköping University, 581 85 Linköping, Sweden.
Christina
C
Ekerfelt
Infectious Diseases, Department of Clinical and Experimental Medicine, Linköping University, 581 85 Linköping, Sweden; Department of Infectious Diseases and Department of Clinical and Experimental Medicine, Linköping University, 581 85 Linköping, Sweden.
Pia
P
Forsberg
Medical Microbiology, Department of Clinical and Experimental Medicine, Linköping University, 581 85 Linköping, Sweden; Department of Clinical Microbiology, Division of Medical Services, Ryhov County Hospital, 551 85 Jönkoping, Sweden.
Per-Eric
PE
Lindgren
D000368:Aged; D000907:Antibodies, Bacterial / Q000097:blood*; D015748:Borrelia burgdorferi Group / Q000302:isolation & purification*; D005260:Female; D005387:Finland / Q000453:epidemiology; D006801:Humans; D062312:Islands; D008193:Lyme Disease / Q000097:blood / Q000453:epidemiology / Q000635:transmission*; D008297:Male; D008875:Middle Aged; D013548:Sweden / Q000453:epidemiology; D064927:Tick Bites
D000907:Antibodies, Bacterial
Asymptomatic infection; Bacterial load; Borrelia burgdorferi sensu lato; Lyme borreliosis; Tick bite; Tick-feeding