A Clear and Present Danger: Tick-borne Diseases in Europe

Paul Heyman; Christel Cochez; Agnetha Hofhuis; Joke van der Giessen; Hein Sprong; Sarah Rebecca Porter; Bertrand Losson; Claude Saegerman; Oliver Donoso-Mantke; Matthias Niedrig; Anna Papa


Expert Rev Anti Infect Ther. 2010;8(1):33-50. 

In This Article

Tick Species in Europe

Ticks are members of the phylum Arthropoda. The subphylum Chelicerata includes the class Arachnida, which on its own contains several subclasses.[17,18] The subclass Acari includes ticks. There are two main families of ticks, the Ixodidae (hard ticks), and Argasidae (soft ticks).[19] The most prevalent European tick species are summarized in Box 1. An excellent book on European tick species by Paul D Hillyard is available.[20] There is evidence that both ixodid and argasid ticks have been in existence since the late Paleozoic era up to the early Mesozoic era. Antecedent forms evolved as obligate external parasites of smooth-skinned reptiles during the late Paleozoic era.[3] Ticks are blood-feeding external parasites of mammals, birds and reptiles throughout the world.[21] Approximately 850 tick species have been described worldwide.[18] Both ixodid and argasid ticks are important vectors of disease-causing microorganisms in humans and animals throughout the world.[22] The family Ixodidae is by far the largest, and medically and economically the most important family, with 13 genera and approximately 650 species. Ticks transmit the widest variety of pathogens of any blood sucking arthropod, including bacteria, rickettsiae, protozoa and viruses.[17] Ixodid ticks have three distinct life stages. Larvae that emerge from the egg are distinguished from later stages (nymph and adult) by possessing only six legs instead of eight. After obtaining a blood meal from a vertebrate host, larvae moult to the nymphal stage, nymphs feed and moult to the next and final adult stage. After feeding once more, the adult female hard ticks lay one batch of a few thousand eggs and dies. The average lifespan of each stage is approximately 8–12 months.[17,23] Only one blood meal is taken during each of the three life stages. The time to completion of the entire lifecycle may vary from less than 1 year in tropical regions to three or more years in the temperate regions, where certain stages may enter a prolonged diapause until hosts become available again.[18] Many hard ticks survive for several months without feeding given favorable environmental conditions. Most Ixodidae have retained their preferences for mammals and birds. Ticks of the genera Amblyomma are most commonly found infesting reptiles.[24,25]