Mapping and monitoring tick (Acari, Ixodida) distribution, seasonality, and host associations in the United Kingdom between 2017 and 2020

Abstract

Tick-borne disease risk is intrinsically linked to the distribution of tick vector species. To assess risk and anticipate disease emergence, an understanding of tick distribution, host associations, and seasonality is needed. This can be achieved, to some extent, using passive surveillance supported by engagement with the public, animal health, and public health experts. The Tick Surveillance Scheme (TSS) collects data and maps tick distribution across the United Kingdom (UK). Between 2017 and 2020, 3720 tick records were received and 39 tick species were detected. Most records were acquired in the UK, with a subset associated with recent overseas travel. The dominant UK acquired species was Ixodes ricinus (Ixodida: Ixodidae, Linnaeus), the main vector of Lyme borreliosis. Records peaked during May and June, highlighting a key risk period for tick bites. Other key UK species were detected, including Dermacentor reticulatus (Ixodida: Ixodidae, Fabricius) and Haemaphysalis punctata (Ixodida: Ixodidae, Canestrini & Fanzago) as well as several rarer species that may present novel tick-borne disease risk to humans and other animals. Updated tick distribution maps highlight areas in the UK where tick exposure has occurred. There is evidence of increasing human tick exposure over time, including during the COVID-19 pandemic, but seasonal patterns remain unchanged.

Keywords: Ixodes ricinus; Lyme borreliosis; citizen science; mapping; public health; recording.

FIGURE 1

Number of records received by the UK Tick Surveillance Scheme (TSS) during 2005–2020, separated by tick species (includes data from Jameson & Medlock,  and Cull et al., 2018). The * represents two records of Hyalomma ticks acquired in the UK.

FIGURE 2

Number of records received by the UK TSS every 2 weeks per month during 2017–2020, separated by tick species.

FIGURE 3

Number of records of Ixodes ricinus on humans (dark blue), dogs (light blue), and cats (grey) received by the TSS between 2005 and 2020.

FIGURE 4

Predicted number of Ixodes ricinus records on humans (dark blue), dogs (light blue), and cats (grey) in 2010–2016 and 2017–2020. Solid lines represent the predicted number of records. Shaded areas represent 95% confidence intervals.

FIGURE 5

Distribution of records of Ixodes ricinus in the UK mapped at 10 km resolution. Grids with I. ricinus presence reported between 2005 and 2016 only are light grey. Those in dark grey had records during 2010–2016, and 2017–2020 and represent persistent reporting of this species in these areas. Grids in blue have records of I. ricinus reported for the first time during 2017–2020 and may indicate new areas of distribution. Contains Ordnance Survey data © Crown copyright and database right 2022. Contains National Statistics data © Crown copyright and database right 2022.

FIGURE 6

Distribution of records of Ixodes hexagonus, Dermacentor reticulatus, and Haemaphysalis punctata in the UK mapped at 10 km resolution. Grids with presence reported between 2005 and 2016 only are light grey. Those in dark grey had records during 2010–2016, and 2017–2020, and represent persistent reporting of this species in these areas. Those in blue have records reported for the first time during 2017–2020 and may indicate new areas of distribution. Contains Ordnance Survey data © Crown copyright and database right 2022. Contains National Statistics data © Crown copyright and database right 2022.

FIGURE 7

Origin of ticks imported into the UK on travelling cats (grey), dogs (light blue), and humans (dark blue) reported to the TSS between 2017 and 2020 (includes data from (Gillingham et al., ; Hansford et al., 2018). Dots on the map may represent one or more records and are not the exact locations where ticks were acquired (they are at country centroids where possible). A a, Amblyomma Americanum; A h, Amblyomma hebraeum; A t, Amblyomma triguttatum; D a, Dermacentor auratus; D m, Dermacentor marginatus; D r, Dermacentor reticulatus; D v, Dermacentor variabilis; H e, Haemaphysalis elliptica; H t, Haemaphysalis tibetensis; Hy a, Hyalomma aegyptium; Hy l, Hyalomma lusitanicum; Hy t, Hyalomma truncatum; I he, Ixodes hexagonus; I ho, Ixodes holocyclus; I r, Ixodes ricinus; I s, Ixodes scapularis; R a, Rhipicephalus appendiculatus; R g, Rhipicephalus gertrudae; R s, Rhipicephalus sanguineus s.l.; R t, Rhipicephalus turanicus. This map was produced using ArcMap 10.5.1 and contains data from Esri, HERE, Garmin, © OpenStreetMap contributors, and the GIS User Community.