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Migratory passerine birds as reservoirs of Lyme borreliosis in Europe.
Umeå University, Faculty of Medicine, Molecular Biology (Faculty of Medicine). (Bergström)
Umeå University, Faculty of Medicine, Molecular Biology (Faculty of Medicine). (Bergström)
Umeå University, Faculty of Medicine, Clinical Microbiology, Infectious Diseases.
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2006 (English)In: Emerging Infectious Diseases, ISSN 1080-6040, Vol. 12, no 7, 1087-95 p.Article in journal (Refereed) Published
Abstract [en]

To define the role of birds as reservoirs and disseminators of Borrelia spirochetes, we characterized tick infestation and reservoir competence of migratory passerine birds in Sweden. A total of 1,120 immature Ixodes ricinus ticks were removed from 13,260 birds and assayed by quantitative polymerase chain reaction (PCR) for Borrelia, followed by DNA sequencing for species and genotype identification. Distributions of ticks on birds were aggregated, presumably because of varying encounters with ticks along migratory routes. Lyme borreliosis spirochetes were detected in 160 (1.4%) ticks. Borrelia garinii was the most common species in PCR-positive samples and included genotypes associated with human infections. Infestation prevalence with infected ticks was 5 times greater among ground-foraging birds than other bird species, but the 2 groups were equally competent in transmitting Borrelia. Migratory passerine birds host epidemiologically important vector ticks and Borrelia species and vary in effectiveness as reservoirs on the basis of their feeding behavior.

Place, publisher, year, edition, pages
2006. Vol. 12, no 7, 1087-95 p.
Keyword [en]
Animals, Bird Diseases/parasitology, Borrelia/classification, Disease Reservoirs, Europe/epidemiology, Lyme Disease/*epidemiology/microbiology, Passeriformes/*microbiology, Tick Infestations/veterinary, Ticks/microbiology
URN: urn:nbn:se:umu:diva-12902PubMedID: 16836825OAI: diva2:152573
Available from: 2008-01-08 Created: 2008-01-08 Last updated: 2011-01-11Bibliographically approved
In thesis
1. Biology of Borrelia garinii Spirochetes
Open this publication in new window or tab >>Biology of Borrelia garinii Spirochetes
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Lyme borreliosis is a tick-transmitted infectious disease. The causative agents are spiral-shaped bacteria and the most common sign of infection is a skin rash at the site of the tick bite. If not treated with antibiotics, the bacteria can disseminate and cause a variety of different manifestations including arthritis, carditis or neurological problems. The disease is a zoonosis and the bacteria are maintained in nature by different vertebrate reservoir host animals. In Europe, three different Borrelia genospecies cause Lyme borreliosis: B. burgdorferi, B. afzelii and B. garinii. The latter depends in part on birds as its reservoir host. B. garinii bacteria have been found in a marine enzootic infection cycle worldwide and also among terrestrial birds. This thesis suggests that passerine birds and seabirds constitute an important reservoir for B. garinii bacteria also with clinical importance. We have found bacteria very similar to Lyme borreliosis causing isolates in ticks infesting migrating passerine birds. The birds not only transport infected ticks, but are competent reservoir hosts, as measured by their ability to infect naïve ticks. Their role as a reservoir host is dependent on their foraging behavior, where ground-dwelling birds are of greater importance than other species. When comparing B. garinii isolates from Europe, the Arctic and North Pacific, and including isolates from seabirds, passerine birds, Ixodes ricinus ticks and Lyme borreliosis patients, we found that phylogenetic grouping was not necessarily dependent on geographical or biological origin. B. garinii from seabirds were very heterogeneous and found in all different groups. Therefore, the marine and the terrestrial infection cycles are likely to overlap. This was supported by the fact that B. garinii isolated from seabirds can establish a long-term infection in mice. Bacteria from the genospecies B. garinii are overrepresented among neuroborreliosis patients. Interestingly, many clinical B. garinii isolates are sensitive to human serum and have shown weak binding to the complement inhibitor protein factor H. By transforming a serum-sensitive B. garinii isolate with a shuttle vector containing the gene for the factor H binding protein OspE from complement-resistant B. burgdorferi, serum resistance could be increased. In addition, neurovirulent B. garinii strains recently isolated from neuroborreliosis patients were shown to express a factor H binding protein, not found in bacteria that had been kept in culture for a long time. This protein may contribute to the virulence of neuroborreliosis-causing B. garinii strains. When testing B. garinii isolates from Lyme borreliosis patients and seabirds for resistance to human serum, all members of the latter group were sensitive to even low levels of serum. This suggests that seabird isolates are not capable of infecting humans. In agreement with this, B. garinii isolated from seabirds do not appear to bind human factor H.

Place, publisher, year, edition, pages
Umeå: Molekylärbiologi (Medicinska fakulteten), 2008. 73 p.
Umeå University medical dissertations, ISSN 0346-6612 ; 1161
Borrelia garinii, Lyme borreliosis, birds, migration, reservoir host, complement, Ixodes ricinus, Europe, Asia, infection cycle
National Category
Biochemistry and Molecular Biology
urn:nbn:se:umu:diva-1578 (URN)978-91-7264-521-9 (ISBN)
Public defence
2008-03-28, Major Groove, 6L, Umeå, 09:00 (English)
Available from: 2008-03-14 Created: 2008-03-14 Last updated: 2011-10-27Bibliographically approved

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