Ticks of the genus Hyalomma mainly live in afrotropical and palearctic regions.
H. marginatum is a vector for some pathogens of medical and veterinary importance like Crimean Congo Hemorrhagic Fever (CCHF) and West Nile virus as well as Rickettsia aeschlimannii, Babesia caballi and Theileria annulata. H. rufipes is the most widespread Hyalomma species in Africa and also known as a vector for the CCHF virus, Rickettsia spp., Anaplasma marginale and Babesia occultans. It is assumed that larvae and nymphs of both tick species are regularly imported by migrating birds to Europe. However, due to current climatic conditions these Hyalomma larvae and nymphs do not develop to adult animals and do not establish permanent populations in Central Europe.

In 2018, ten H. marginatum and eight H. rufipes specimens have been found in various regions of Germany (Federal States of Baden-Wuertemberg, Hesse, Rhineland-Palatine, Lower Saxony and Schleswig-Holstein). An additional seventeen ticks have been identified as Hyalomma based on photos (Chitimia-Dobler et al., 2019). All reported and confirmed tick findings were in western Germany along the main western migratory route of birds from West Africa via Spain and France to Scandinavia. 2018 was the warmest and second driest year in Germany since the beginning of weather recording in 1881 favoring the development of imported Hyalomma nymphs to adult animals.

Tests for the CCHF virus, Coxiella burnetii (the agent of Q fever), Coxiella-like organisms, Babesia spp. and Theileria spp. revealed negative. However, nine ticks were tested positive for rickettsiae using a pan-Rick PCR test and by further analyses R. aeschlimannii has been identified. R. aeschlimannii is a member of the spotted fever group and is an important human pathogen. Six of seven ompA1 sequences obtained from the German samples showed to be 100% identical to strains from different areas of the world (Russia, Israel, Spain, Portugal, Turkey), while one sample was identical to a sequence found in Senegal.

In parallel to the investigations by Chitimia-Dobler et al., 2019), nineteen Hyalomma ticks found in various Federal States in Germany have been analyzed by Hagedorn (2019) for the presence of Anaplasma phagocytophilum, Borrelia burgdorferi, Babesia spp., Candidatus Neoehrlichia mikurensis and Rickettsia spp., but none of these pathogens could be identified in the nineteen ticks.

In 2018, adult Hyalomma ticks have not only been found in Germany. In October 2018, a male H. marginatum tick was removed from a horse in the State of Lower Austria. In this tick, R. aeschlimannii could be identified, but no other pathogen (Duscher et al., 2018).

In the context of Hyalomma ticks being imported by migrating birds to Central Europe, it should be noted that recently, the CCHF virus has been identified in a H. rufipes nymph collected from a bird (Saxicola rubetra) on the island of Ventone, Italy, in April 2017 (Mancuso et al., 2019).

So far this year, six Hyalomma ticks have been found in Germany, five from a horse farm in North Rhine-Westphalia and one tick from a horse in Lower Saxony (Universität Stuttgart-Hohenheim, 2019). It is suspected that these ticks have overwintered in Germany. Overwintering of Hyalomma ticks does not automatically mean that this tick genus has established itself in Germany, because it is difficult for male and female ticks to find each other for copulation at such a low population density. However, as five Hyalomma ticks have been found at one horse farm, this makes it possible that a discrete population arises in a given area.

While many or even countless larvae and nymphs of Hyalomma ticks may be imported yearly by migrating birds to Germany and other Central European countries and Scandinavia, these usually do not develop to adult ticks because of unfavorable climatic conditions for this tick genus. 2018 was an uncommonly dry and hot year in Central Europe, such that living conditions for Hyalomma became excellent and nymphs could develop to adult ticks. It seems that adult Hyalomma ticks have overwintered in Germany, and now the question arises, if Hyalomma can establish itself at least in some regions of Germany with a mild climate, or if the occurrence of adult Hyalomma ticks in 2018 remains a singular phenomenon.

Chitimia-Dobler et al.
Imported Hyalomma ticks in Germany in 2018
Parasit. Vectors 2019; 12:134, DOI: 10.1186/s13071-019-3380-4

Duscher et al.
Adult Hyalomma marginatum tick positive for Rickettsia aeschlimannii in Austria, October 2018
Euro Surveill. 2018; 23 (48):pii=1800595.

Hagedorn, D.
Fund von Zecken der Gattung Hyalomma in Deutschland
(Discovery of ticks of the genus Hyalomma in Germany)
Epid. Bull. 2019; 7:70-71, DOI: 10.25646/5893

Mancuso et al.
Crimean-Congo Hemorrhagic Fever virus in tick from migratory bird, Italy
Emerg. Infect. Dis. 2019, in press, DOI: 10.3201/eid2507.181345

Universität Stuttgart-Hohenheim
Tropische Zecken: Neu eingewanderte Art überwintert erstmals in Deutschland
(Tropical ticks: Newly immigrated species overwintered for the first time in Germany)
Pressemitteilung (press release) 11. 06. 19

Author: Dr. Michael Bröker

Michael Bröker is a microbiologist/biochemist by training. He has more than 35 years of experience in the field of biotechnology and vaccinology while working for various pharmaceutical companies. He also worked as curator and expert in committees of foundations, scientific boards and associations as well as for companies.

Compiled: June 2019

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