Blood-sucking ticks (Acarina,Ixodoidea) as an essential component of the urban environment

The problem of urban ticks has arisen from the increased rate of urbanization since WWII. Expansion of municipal boundaries encompasses adjacent territories, so that large areas of wilderness together with all their inhabitants get incorporated into city limits. Current strategies of biodiversity conservation include the creation of green corridors and other forms of connectivity between wilderness and urban areas as well as between green patches within cities. All this allows various mammals and birds to migrate from their native habitats into and between various parts of the cities and to establish permanent urban populations. Medium-sized and larger animals provide adult ticks with blood meal, thus creating suitable conditions for the establishment and persistence of tick populations. Independent tick populations can exist in urban forests, parks, private properties, old cemeteries, etc. Over the last decades, the tick populations that originated from those in natural habitats around the cities have become a permanent component of urban fauna. Among such ticks, the castor bean tick Ixodes ricinus is the most important species for European cities, while the deer tick I. scapularis is of great significance for the East Coast of the United States. The taiga tick I. persulcatus is the most important species for the Russian cities and towns within its range. All these and some other ticks aggressively attack humans and their pets inside cities. The tick species especially well adapted to urban life are those which can live and reproduce in buildings. The brown dog tick Rhipicephalus sanguineus (family Ixodidae), the pigeon ticks from the reflexus group of the genus Argas, and Ornithodoros ticks (family Argasidae), which form urban and semi-urban populations, are the main urban tick pests and vectors. House infestation by ticks can lead to human infection with tick-borne pathogens or severe allergic reactions. Some tick hosts, mammals as well as birds, maintain tick-transmitted pathogens and serve as competent reservoir hosts. Urban populations of these animals can participate in the circulation of some pathogens within cities. Thus, the enlargement of urban green areas followed by their population by wild mammals and birds create good opportunities for the establishment of urban populations of tick vectors with the resulting threat to the health of urban dwellers and their pets. At the same time, our understanding of the real scope and complexity of the problem of urban ticks is far from being sufficient. Finding the ways of protecting the environment without increasing the risk to human health in modern cities is a pressing and challenging problem of our time.