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Ticks Tick Borne Dis. 2019 Sep 22:101303. doi: 10.1016/j.ttbdis.2019.101303. [Epub ahead of print]

Emerging tick-borne pathogens in the Nordic countries: A clinical and laboratory follow-up study of high-risk tick-bitten individuals.

Author information

1
Department of Bacteria, Parasites and Fungi, Statens Serum Institut, Artillerivej 5, 2300 Copenhagen, Denmark; Department of Virus and Microbiological Special Diagnostics, Statens Serum Institut, Artillerivej 5, 2300 Copenhagen, Denmark; Department of Clinical Microbiology, Rigshospitalet, Blegdamsvej 9, 2100 Copenhagen, Denmark. Electronic address: luoc@ssi.dk.
2
Division of Medical Microbiology, Department of Clinical and Experimental Medicine, Linköping University, 58183 Linköping, Sweden; Department of Clinical Microbiology, County Hospital Ryhov, Sjukhusgatan, 55305 Jönköping, Sweden.
3
Clinic of Infectious Diseases, Linköping University Hospital, 58185 Linköping, Sweden.
4
Division of Medical Microbiology, Department of Clinical and Experimental Medicine, Linköping University, 58183 Linköping, Sweden; Department of Clinical Microbiology, County Hospital Ryhov, Sjukhusgatan, 55305 Jönköping, Sweden; Department of Clinical Microbiology, Linköping University Hospital, 58185 Linköping, Sweden.
5
The Åland Group for Borrelia Research, Åland Central Hospital, Doktorsvägen 2, 22110 Mariehamn, Åland, Finland.
6
Department of Virus and Microbiological Special Diagnostics, Statens Serum Institut, Artillerivej 5, 2300 Copenhagen, Denmark.
7
Department of Bacteria, Parasites and Fungi, Statens Serum Institut, Artillerivej 5, 2300 Copenhagen, Denmark; Department of Virus and Microbiological Special Diagnostics, Statens Serum Institut, Artillerivej 5, 2300 Copenhagen, Denmark; Department of Science and Environment, Roskilde University, Universitetsvej 1, 4000 Roskilde, Denmark.
8
Division of Infectious Medicine, Department of Clinical and Experimental Medicine, Linköping University, 58183 Linköping, Sweden.

Abstract

Despite the presence of several microorganisms, other than Borrelia burgdorferi sensu lato (Bbsl) and TBE virus, in Ixodes ricinus ticks from the Nordic countries, data is lacking on their pathogenic potential in humans. In this study, we wanted to investigate the aetiology and clinical manifestations of tick-transmitted infections in individuals seeking medical care following a tick-bite. The sampling frame was participants of a large-scale, prospective, multi-centre, follow-up study of tick-bitten volunteers recruited in Sweden, Finland and Norway in the years 2007-2015. Participants who sought medical care during the three-month follow-up period and from whom blood samples were collected during this healthcare visit (n = 92) were tested, using PCR, for exposure to spotted fever group (SFG) Rickettsia spp., Anaplasma phagocytophilum and Babesia spp. Moreover, 86 of these individuals had two serum samples, collected three months apart, tested serologically for six tick-borne microorganisms. The selected organisms - Bbsl, SFG rickettsiae, Anaplasma phagocytophilum, TBE virus, Babesia microti and Bartonella henselae - have all been detected in field-collected ticks from the Nordic countries. Medical records were reviewed and questionnaires were completed to determine clinical manifestations. We found Lyme borreliosis to be the most common tick-transmitted infection as seen in 46 (54%) of the 86 participants with available medical records. Among the 86 participants with paired sera, serological or molecular evidence of recent exposure to other microorganisms than Bbsl could be demonstrated in eight (9%). Five participants (6%) exhibited serological evidence of recent concomitant exposure to more than one tick-borne microorganism. Clinical presentations were mild with one exception (TBE). In conclusion, our data suggest a low risk of infection with tick-borne microorganisms, other than Bbsl, in immunocompetent tick-bitten persons from the examined regions, a low occurrence of co-infection and mostly mild or no overt clinical signs of infection in immunocompetent persons exposed to the studied agents.

KEYWORDS:

Co-infections; Emerging infections; Public health; Tick-borne pathogens; Tick-transmitted infections; Vector-borne infections

PMID:
31631052
DOI:
10.1016/j.ttbdis.2019.101303
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