Ticks are important blood-feeding external parasites of mammals, birds and reptiles throughout the world, with however very different species of relevance regionally.
All stages of the tick developmental cycle (larva, nymph and adult) are parasitic on vertebrates.
It is suggested that both ixodid and argasid ticks have been in existence since the late Paleozoic to early Mesozoic eras (Hoogstraal and Kim, 1985).
Ticks are members of the same phylum (Arthropoda) of the animal kingdom as insects, however they are in a different class.
The subphylum Chelicerata includes the class Arachnida, which again contains several subclasses. The subclass Acari (syn. Acaria, Acarina, Acarida) includes ticks.
A characteristic of the Acarines is the extreme fusion of body segments, in contrast to the known three body segments head, thorax and abdomen in insects.
Taxonomy of ticks
|Subclass:||Acaria (Acari, Acarina, Acarida)|
|Order:||Anactinotrichidea (= Parasitoformes)|
|Suborder:||Ixodida (= Metastigmata)|
|Family||Ixodidae (Hard Ticks) |
Argasidae (Soft Ticks)
The Acari are subdivided into the order Parasitiformes and Acariformes.
The order Parasitiformes to which ticks belong have stigmatal pores on the podosoma part (leg-bearing portion) and free articulated coxae (Sonenshine, 1991).
Their suborder is Metastigmata, as their stigmen can be found behind coxa III or behind coxa IV. Its members are obligate blood-sucking parasites which have the following common features:
- Haller's organ - a complex sensory organ, on tarsus I
- Ventral toothed hypostome
- Chelicera of only two joints
- Peritreme around the stigmen
The order Metastigmata comprises three families: the Ixodidae (hard ticks), the Argasidae (soft ticks), and the Nuttalliellidae.
The Nuttalliellidae are represented only by a single species, Nutalliella namaqua; found in South and South-West Africa as a parasite of small mammals. Thus, the two tick families of relevance are Ixodidae (hard ticks) and Argasidae (soft ticks) (Pfister, 2006; Sonenshine, 1991).
The accurate identification of tick species is an important factor in the detection and diagnosis of tick-borne diseases and is a prerequisite for tick control (Cupp, 1991).