The ticks are obligate, blood-feeding ectoparasites of vertebrates, particularly mammals and birds. Ticks are arachnids, in the sub-class Acari, closely related to the mites. They are usually relatively large and long-lived compared to mites, surviving for up to several years. During this time they feed periodically taking large blood meals, often with long intervals, spent off the host, between each meal. Since a large proportion of the life-cycle of most tick species occurs off the host, the habitat in which they live is of particular importance. The tick habitat must satisfy two main requirements: there must be a large enough concentration of host species for each of the developmental instars to locate a new host and a sufficiently high humidity for the ticks to maintain their water balance. In areas where the humidity is low, ticks resist desiccation by spending shorter periods questing for hosts. They also enter diapause at unfavourable times of the year. Dormancy is initiated by changes in day length and temperature.
Tick bites can be directly debilitating to domestic animals, causing mechanical damage, irritation, inflammation and hypersensitivity and, when present in large numbers, feeding may cause anaemia and reduced productivity. The salivary secretions of some tick species may cause toxicosis and paralysis. Ticks may also transmit a range of pathogenic viral, rickettsial and bacterial diseases to livestock. Hence, although the ticks are a relatively small order of only about 800 species, they are one of the most important groups of arthropod pests of veterinary interest.
Wall, R. & Shearer, D. (2001) Veterinary Ectoparasites: Biology, Pathology and Control. 2nd Edition, Blackwells Science Ltd, Oxford.
Pitts, K. & Wall, R (2003) Publication in press.