3 research outputs found
Surveillance of Ixodes ricinus ticks (Acari: Ixodidae) in Iceland
Background: Ixodes ricinus is a three-host tick, a principal vector of Borrelia burgdorferi (s.l.) and one of the main
vectors of tick-borne encephalitis (TBE) virus. Iceland is located in the North Atlantic Ocean with subpolar oceanic
climate. During the past 3–4 decades, average temperature has increased, supporting more favourable conditions
for ticks. Reports of I. ricinus have increased in recent years. If these ticks were able to establish in a changing
climate, Iceland may face new threats posed by tick-borne diseases.
Methods: Active field surveillance by tick flagging was conducted at 111 sites around Iceland from August 2015 to
September 2016. Longworth mammal traps were used to trap Apodemus sylvaticus in southwestern and southern
Iceland. Surveillance on tick importation by migratory birds was conducted in southeastern Iceland, using bird nets
and a Heligoland trap. Vulpes lagopus carcasses from all regions of the country were inspected for ticks. In addition,
existing and new passive surveillance data from two institutes have been merged and are presented. Continental
probability of presence models were produced. Boosted Regression Trees spatial modelling methods and its
predictions were assessed against reported presence.
Results: By field sampling 26 questing I. ricinus ticks (7 males, 3 females and 16 nymphs) were collected from
vegetation from three locations in southern and southeastern Iceland. Four ticks were found on migratory birds at their
arrival in May 2016. A total of 52 A. sylvaticus were live-trapped but no ticks were found nor on 315 V. lagopus carcasses.
Passive surveillance data collected since 1976, reports further 214 I. ricinus ticks from 202 records, with an
increase of submissions in recent years. The continental probability of presence model correctly predicts
approximately 75% of the recorded presences, but fails to predict a fairly specific category of recorded
presence in areas where the records are probably opportunistic and not likely to lead to establishment.
Conclusions: To the best of our knowledge, this study represents the first finding of questing I. ricinus ticks
in Iceland. The species could possibly be established locally in Iceland in low abundance, although no
questing larvae have yet been detected to confirm established populations. Submitted tick records have
increased recently, which may reflect an increase in exposure, or in interest in ticks. Furthermore, the
amount of records on dogs, cats and humans indicate that ticks were acquired locally, presenting a local
biting risk. Tick findings on migratory birds highlight a possible route of importation. Obtaining questing
larvae is now a priority to confirm that I. ricinus populations are established in Iceland. Further surveys on
wild mammals (e.g. Rangifer tarandus), livestock and migratory birds are recommended to better understand
their role as potential hosts for I. ricinus.Work was carried out under VectorNet, a European network for sharing data on the geographic distribution of arthropod vectors, transmitting human and animal disease agents (framework contract OC/EFSA/AHAW/2013/02-FWC1) funded by the European Food Safety Authority (EFSA) and the European Centre for Disease prevention and Control (ECDC). JM is also partly funded by the National Institute for Health Research Health Protection Research Unit (NIHR HPRU) in Environmental Change and Health at the London School of Hygiene & Tropical Medicine in partnership with Public Health England (PHE), and in collaboration with the University of Exeter, University College London, and the Met Office; and partly funded by the NIHR HPRU on Emerging Infections and Zoonoses at the University of Liverpool in partnership with PHE and Liverpool School of Tropical Medicine.Peer Reviewe