New publication: Lyme neuroborreliosis and bird populations in northern Europe
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.
Proceedings of the Royal Society B.
Published online: 29 May 2019
* Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biosciences, University of Oslo, Oslo, Norway.
See the publication webpage for full author information.