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SECTION 6 - TICKS
Intoduction
The most common vector-borne diseases in Europe are transmitted by ticks. Incidence of tick-borne diseases can be lowered by active public education campaigns, targeted at the times and places of greatest potential for encounter between humans and infected ticks.
Habitat
Ticks dwell predominantly in woodlands and meadows, and in association with animal hosts, with only limited colonization of human dwellings by a few species. The current trend towards urban spread into the countryside could potentially result in increases in transmission of tick-borne diseases.
Health Impact
The most common vector-borne diseases in both Europe and are transmitted by ticks. Lyme borreliosis ( LB), a tick-borne bacterial zoonosis, is the most highly prevalent. Other important tick-borne diseases include TBE (tick-borne encephalitis) and Crimean-Congo haemorrhagic fever in Europe and numerous less common tick-borne bacterial, viral, and protozoan diseases. There are several related species of Borrelia and they differ in clinical manifestations, ecology (for example, some have primarily avian and others primarily mammalian reservoirs), and transmission cycles.
Nuisance
Ticks are controlled for a variety of reasons, including nuisance prevention, commodity protection (to prevent cattle loss, for example) and protection against TBDs.
Habitat manipulation and urban design
Ticks have species-specific habitat requirements, often associated with habitats of hosts and the need to avoid desiccation. Therefore, habitats can be manipulated to make them unsuitable for ticks or to minimize encounters between ticks and people.
Suburban habitats associated with natural woodlands foster populations of black-legged ticks and castor-bean ticks, because these habitats are excellent for both immature and adult ticks and for vertebrate hosts suitable for all tick stages. Maintaining a short-clipped lawn and establishing barriers to prevent access to the woods can minimize human exposure to ticks in this environment. Mowing and burning vegetation in natural areas lowers tick numbers temporarily, but ticks reinfest treated areas as the vegetation grows back. Most ticks that are important to human health are rare in highly urbanized environments but exposure in parks and natural habitats can be minimized with appropriate design features, such as barriers between areas frequently used by people and natural patches, and pathways constructed through natural sites.
Host-centred methods
Domestic animals can be vaccinated to minimize tick attachment or to protect them against TBDs. Manipulation of host populations can also lower tick populations. Excluding deer can lower populations of deer ticks, and deer-proof fencing can contribute to a tick management programme.
Pesticide applications
Numerous pesticides are effective against ticks, and they are widely used to control ticks and TBDs. Acaricides can be broadcast for area control of ticks or can be targeted at host animals used by the ticks. Broadcast applications have the advantage that they can rapidly lower tick numbers, but timing, chemical distribution and formulation can profoundly influence the effectiveness of treatment. Most materials used for tick control are broadly toxic to arthropods, so broadcast applications can have substantial effects on non-target species.
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