Ticks are economically important ectoparasites of domestic and wild animals and are considered to be second worldwide to mosquitoes as vectors of human pathogens. Current control methods for ticks, based primarily on the use of
acaricides, have had limited efficacy in the reduction of
tick infestations and the use of
acaricides is often accompanied by serious drawbacks, including selection of
acaricide-resistant ticks and environmental contamination. Development of improved
vaccines against
tick infestations offers a cost-effective and environmentally sound control method. Commercial
vaccines currently marketed for control of cattle ticks have been effective in field studies when used in concert with integrated control strategies. However, new
antigens are needed to increase the efficacy of tick
vaccines. Although a limited number of protective
antigens against
tick infestations have been identified and characterized, discovery of new
antigens remains the limiting step for improving the efficacy of tick
vaccines. Recent technologies developed for gene discovery, including expression library immunization and evaluation of expressed sequence tags, show promise for rapid, systematic and global
antigen screening and should provide a comprehensive approach to selection of candidate
vaccine antigens. Design of future tick
vaccines should target multiple tick species, as well as interfere with the transmission of pathogens.