ABSTRACT
Ticks are haematophagous ectoparasites, and thus belong to parasitology. This chapter introduce ticks in general, emphasizing their mode of life and interrelations with their hosts. The life of an individual tick is characterized by a succession of ectoparasitic and free-living phases. All ticks' life cycles consist of four succeeding stages: the egg, the larva, the nymph(s) and the adult. A surprisingly wide variety of pathogens are transmitted by ticks. Among the metazoans transmitted by ticks one finds filarial helminths such as Acanthocheilonema and Macdonaldius. A natural transmission focus has been defined as the smallest area which permits sustaining the complete life cycle of a pathogen over longer periods of time. Except for a few species originating from dry areas, ticks are rather susceptible to low humidity and desiccation. Some species, e.g. I. ricinus, easily withstand temperatures as low as 5°C; pathogens present in such ticks, too, will remain viable for several days after collection of the ticks.
