Millins C1,2,
Gilbert L3,
Johnson P4,5,
James M6,7,8,
Kilbride E4,
Birtles R9,
Biek R4,5.
- 1Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, Scotland. Caroline.Millins@glasgow.ac.uk.
- 2The
Boyd Orr Centre for Population and Ecosystem Health, University of
Glasgow, Glasgow, Scotland. Caroline.Millins@glasgow.ac.uk.
- 3James Hutton Institute, Craigiebuckler, Aberdeen, Scotland.
- 4Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, Scotland.
- 5The Boyd Orr Centre for Population and Ecosystem Health, University of Glasgow, Glasgow, Scotland.
- 6Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen, UK.
- 7Division of Applied Medicine, University of Aberdeen, Aberdeen, UK.
- 8Present Address: Food Standards Scotland, Aberdeen, Scotland.
- 9School of Environment and Life Sciences, University of Salford, Salford, UK.
Abstract
BACKGROUND:
Cases
of Lyme borreliosis, a vector-borne zoonosis caused by bacteria in the
Borrelia burgdorferi (sensu lato) species group, have increased in
recent years in Europe. Knowledge of environmental factors associated
with abundance of the tick vector Ixodes ricinus and the pathogen B.
burgdorferi (s.l.) is of interest to understand responses to
environmental changes, predict variation in risk and to inform
management interventions.
METHODS:
Nineteen
woodland sites across Scotland were surveyed in 2012 for B. burgdorferi
(s.l.) infection in questing I. ricinus nymphs (n = 200 per site), deer
abundance and vegetation. Climatic factors were extracted for each
site. Six additional sites were surveyed for questing nymphs in both
2012 and 2013 (n = 200 per site and year) to test for variation in B.
burgdorferi (s.l.) prevalence between years.
RESULTS:
The
mean prevalence of B. burgdorferi (s.l.) across 19 sites was 1.7% (95%
CI: 1.4-2.2%; range 0-6%), all four genospecies known to be present in
the UK were detected: B. garinii, B. afzelii, B. burgdorferi (sensu
stricto) and B. valaisiana. A higher prevalence of B. burgdorferi
(s.l.), higher densities of nymphs and higher densities of infected
nymphs were found at sites with warmer climates, estimated with growing
degree-days. No association between infection prevalence in nymphs and
woodland type (semi-natural mixed vs coniferous) or deer density was
found. At six sites sampled in 2012 and 2013, there was a significant
increase in B. afzelli prevalence at two sites and a decrease in B.
garinii prevalence at one site.
CONCLUSIONS:
This
study highlights challenges for the prediction of risk of Lyme
borreliosis, reflecting the sensitivity of both pathogen and vector
ecology to habitat, host and climatic factors. Significant changes in
the prevalence of individual genospecies at sites monitored across time
are likely to be due to variability in the host community composition
between years. Our results indicate the importance of monitoring dynamic
variables such as reservoir host populations as well as climate and
habitat factors over multiple years, to identify environmental factors
associated with Lyme borreliosis risk.
KEYWORDS:
Borrelia burgdorferi; Host community; Ixodes ricinus; Risk prediction; Spatial heterogeneity
