MANAGEMENT, CONTROL AND REGULATIONS

Management and control of LB may be directed against the vectors or the pathogen itself (see ⁽⁵⁴⁾ and ⁽⁵⁵⁾ for reviews). In humans, public education; personal protec­tion measures such as wearing protective clothing, check­ing one’s body daily for ticks (as early removal reduces the risk of infection), avoiding tick-infested areas, and apply­ing tick repellent is used to diminish risks of infection.

Individual protection of livestock and domestic animals is commonly achieved by use of topical acaricides. However, effective and long-lasting measures against I. ricinus and Borrelia sp. have to be directed against the natural habitats and the hosts of the ticks.

One major approach will be to manipulate tick habitats in order to expose the free-living ticks to low relative humidity and soil moisture by mechanical clearing of veg­etation, use of herbicides, intensive grazing by livestock, removal of leaf litter and controlled burns.

Another principal approach would be to protect natural hosts against ticks and/or borrelia. Treatment of hosts such as cervids with acaricides in automatic-application devices should be expected to cause a decline in the tick popula­tion by reducing the reproductive success of adult ticks. Experience from trials aimed at reducing the populations I. scapularis on white- tailed deer in USA point to this approach as safe, efficacious, economical and environmen­tally friendly⁽⁵⁶⁾. Application of acaricides to small mam­malian hosts through a baited box has the potential not only to impact tick abundance, but also to disrupt the transmission cycle of some borrelial genospecies.

A third approach would be to lower the populations of hosts, either by fencing or hunting. As deer feed such a large proportion of adult ticks, reduction of deer popula­tion is advocated to reduce reproductive success of I. ricinus. It remains unclear, however, how far a deer popula­tion must be reduced to impact the transmission dynamics of LB. It is important to emphasize that the number of questing ticks will increase in the first years after deer population reduction, as fewer deer remove adult ticks from the environment. Also, removal of a large, presum­ably reservoir-incompetent, host may cause more subadult ticks to feed on reservoir-competent hosts. If there is some kind of ecological competition between deer and a host­transmitting pathogenic LBS, a reduction in deer numbers may potentially cause an increase in risk of human disease. Management, habitat manipulation or management to reduce or possibly exclude small mammals, birds and/or lizards to control ticks and Borrelia has not been well studied, but in theory would be a logical approach in some circumstances.

There are currently no effective and widely applicable biological control methods available for the control of tick populations. Entomopathogenic fungi (Beauveria spp., Verticillum spp., Metarhizium spp.), nematodes (Mermith- idae, Heterorhabditidae, Steinernematidae) and parasitoid wasps (Ixodiphagus spp.) seem to be the most promising candidates. (See Hartelt and others, 2008⁽⁵⁷⁾, for a recent review). Bacteria (i.e. Bacillus thuringensis) have also been proposed as potential agents. Chemical control by area­wide use of pesticides has been shown to provide relatively consistent, highly effective short-term suppression of ticks. However, public acceptance of area applications of syn­thetic chemicals for tick control appears relatively low. An alternative approach would be to use tick pheromones and related chemicals. These potential tools could theoretically be applied to disrupt tick behaviour or reproduction without deleterious consequences for the environment, for example by attracting ticks to a toxicant or a baited decoy system.