TICKS (ACARI: IXODOIDEA) AND THEIR MEDICAL IMPORTANCE IN THE URBAN ENVIRONMENT

Abstract:
Ticks (Acari: Ixodoidea) are worldwide prominent pests as haematophagous parasites on humans and domestic animals. This paper emphasizing the central European situation, outlines the biology and the medical significance of four tick species which have often succeeded to colonize suburban environments, and describes the ecological circumstances of their occurrence. Tick species found in towns in central Europe are Argas reflexus (Argasidae), and Ixodes ricinus and I. hexagonus (Ixodidae). Rhipicephalus sanguineus, is occasionally transported unrecognized on pet dogs from southern countries to central Europe. A. reflexus was originally a Mediterranean species. Under central European conditions it lives exclusively in human buildings with nearby nesting feral pigeons. If the natural host is not available, humans are bitten. I. ricinus is the main European vector of Borrelia burgdorferi s.l. and the tick-borne encephalitis (TBE) virus. This tick penetrates into towns by colonizing new and old „green islands“ in the urban environment, where the microclimatic humidity requirements are met, especially in the permanent leaf-litter of forest stands. Transportation of ticks into towns takes place on mobile vertebrate hosts, probably mainly on birds. I. ricinus adults are exclusively found on mammals. The rarity of these animals in towns, suburban hedgehogs seem to be most important for adult tick feeding. Suburban I. ricinus populations are frequently infected with B. burgdorferi and sometimes also with TBE-virus. I. hexagonus parasitizes members of the Carnivora and hedgehogs and is common in suburban locations in central Europe. It spends its non-parasitic phases in the burrows/nests of its hosts. Bites in humans are rare, and it is a proven vector of both B. burgdorferi and TBE virus, and might support the establishment of these agents in the urban environment.