Imported Hyalomma Ticks in The Netherlands 2018-2020

Abstract

Background: Ticks of the genus Hyalomma, which are vectors for several tick-borne diseases, are occasionally found in areas outside their endemic range including northern parts of Europe. The objective of this study was to analyse adult Hyalomma ticks that were recently found in The Netherlands. Methods: Hyalomma ticks were morphologically identified. Cluster analysis based upon sequence data (cox1 barcoding) for molecular identification and pathogen detection was performed. Additionally, a cross-sectional survey among horses was conducted to actively search for Hyalomma ticks in summer 2019. Analysis of temperature was done to assess the possibility of i) introduced engorged nymphs moulting to adults and ii) establishment of populations in The Netherlands. Results: Seventeen adult Hyalomma ticks (one in 2018, eleven in 2019, five in 2020) were found by citizens and reported. Fifteen ticks were detected on horses and two on humans. Twelve were identified as H. marginatum, one as H. rufipes and four, of which only photographic images were available, as Hyalomma sp. No Crimean-Congo Hemorrhagic Fever virus or Babesia/Theileria parasites were detected. One adult tick tested positive for Rickettsia aeschlimannii. In the cross-sectional horse survey, no Hyalomma ticks were found. Analysis of temperatures showed that engorged nymphs arriving on migratory birds in spring were able to moult to adults in 2019 and 2020, and that cumulative daily temperatures in The Netherlands were lower than in areas with established H. marginatum populations. Conclusions: Our results show that Hyalomma ticks are regularly introduced in The Netherlands as nymphs and these are able to develop to the adult stage under the Dutch weather conditions. Vigilant citizens can notify Hyalomma adult ticks, especially when attached to horses. Only one human pathogen, Rickettsia aeschlimannii, was found in one of the ticks. The risk of introduction of tick-borne diseases via Hyalomma ticks on migratory birds is considered to be low.

Ornithological and molecular evidence of a reproducingHyalomma rufipespopulation under continental climate in Europe

“…However, birds usually carry immature ticks, larvae and nymphs of Hyalomma species [5], therefore in case of these thermophilic ticks, another crucial prerequisite prior to establishment is the ability of nymphs detaching from birds to molt to adults. This was already reported for both Hyalomma marginatum and Hyalomma rufipes from several countries north of the Mediterranean Basin, as exemplified by the UK [6] and the Netherlands [7] in western Europe, or Hungary in central Europe [8]. Consequently, Hyalomma adults might also overwinter [9], increasing the chances for future establishment of permanent, reproductive populations.…”

Emergence of Hyalomma marginatum and Hyalomma rufipes adults revealed by citizen science tick monitoring in Hungary

“…Hyalomma often parasitize large domesticated mammals in their adult stages, as was previously known (Hornok & Horváth, 2012;Uiterwijk et al, 2021). It would therefore be worthwhile next year for the program to target inspections of establishments affected in this respect.…”

“…Unfed adult Hyalomma ticks tolerate the cold months well, with the most critical period being late summer and autumn due to the heat sensitivity of engorged nymphs (Uiterwijk et al, 2021;Valcárcel et al, 2020). Thus, it is not the cold winter but the cold autumn that is critical in shaping the geographical spread of Hyalomma species.…”

“…rufipes were retrieved in Hungary (Hornok & Horváth, 2012). The adults of both tick species have recently been detected the Czech Republic (Hubálek et al, 2020;Lesiczka et al, 2022;Rudolf et al, 2021), Germany (Chitimia-Dobler et al, 2019), Sweden (Grandi et al, 2020), the United Kingdom (Hansford et al, 2019;McGinley et al, 2021) and the Netherlands (Uiterwijk et al, 2021).…”

“…It is also a great advantage that a project can be carried out over a large geographical area for many years (MacPhail & Colla, 2020). This approach has been successfully used in searching for the emergence of Hyalomma adults in several European countries (Grandi et al, 2020;Lesiczka et al, 2022;Uiterwijk et al, 2021).…”