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Proc Biol Sci. 2019 May 29;286(1903):20190759. doi: 10.1098/rspb.2019.0759. Epub 2019 May 29.

Lyme neuroborreliosis and bird populations in northern Europe.

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1 Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biosciences, University of Oslo , PO Box 1066, Blindern, 0316 Oslo , Norway.
2 Evolutionary Ecology Group, Department of Biology, University of Antwerp , Universiteitsplein 1, 2610 Wilrijk , Belgium.
3 Interuniversity Institute for Biostatistics and Statistical Bioinformatics, Hasselt University , Diepenbeek , Belgium.
4 Department of Ecology and Evolutionary Biology, Princeton University , Princeton, NJ , USA.
5 Lista Bird Observatory , 4563 Borhaug , Norway.
6 Department of Food, Water, Zoonotic and Vector-borne Infections, The Norwegian Public Health Institute , PO Box 4404, Nydalen, 0403 Oslo , Norway.
7 Norwegian Veterinary Institute , PO Box 750, Sentrum, 0106 Oslo , Norway.


Many vector-borne diseases are transmitted through complex pathogen-vector-host networks, which makes it challenging to identify the role of specific host groups in disease emergence. Lyme borreliosis in humans is now the most common vector-borne zoonosis in the Northern Hemisphere. The disease is caused by multiple genospecies of Borrelia burgdorferi sensu lato bacteria transmitted by ixodid (hard) ticks, and the major host groups transmit Borrelia genospecies with different pathogenicity, causing variable clinical symptoms in humans. The health impact of a given host group is a function of the number of ticks it infects as well as the pathogenicity of the genospecies it carries. Borrelia afzelii, with mainly small mammals as reservoirs, is the most common pathogen causing Lyme borreliosis, and it is often responsible for the largest proportion of infected host-seeking tick nymphs in Europe. The bird-borne Borrelia garinii, though less prevalent in nymphal ticks, is more likely to cause Lyme neuroborreliosis, but whether B. garinii causes disseminated disease more frequently has not been documented. Based on extensive data of annual disease incidence across Norway from 1995 to 2017, we show here that 69% of disseminated Lyme borreliosis cases were neuroborreliosis, which is three times higher than predicted from the infection prevalence of B. garinii in host-seeking ticks (21%). The population estimate of migratory birds, mainly of thrushes, explained part of the annual variation in cases of neuroborreliosis, with a one-year time lag. We highlight the important role of the genospecies' pathogenicity and the host associations for understanding the epidemiology of disseminated Lyme borreliosis.


Lyme borreliosis; birds; epidemiology; genospecies; host populations; tick-borne diseases

[Available on 2020-05-29]

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