Page 219 - The Veterinary Laboratory and Field Manual 3rd Edition

188 Susan C. Cork and Mani Lejeune

Figure 3.40 Typical tick life cycle. (A) Adult male
and (B) female mate, (C) the female takes a large
blood meal and lays her eggs in the environment.
(D) A larva develops from each egg, (E) this feeds
and moults to form a nymph. The nymph feeds and
moults to form an adult (A or B).

Figure 3.41 Life cycle of a three-host tick (for example, some Rhipicephalus sp., Ixodes sp.). These ticks can
feed on three individual hosts separated by long periods in the vegetation where moulting to the next stage
of the life cycle and egg laying occurs. Unfed ticks appear flat but when fed the abdominal area expands to
5–10 times the original size. Feeding at each stage may take a few days to several weeks. Females mate
once and take an enormous meal before detaching to die after laying eggs in the vegetation. In most cases
the aim of tick control is to kill the adult females before they detach and contaminate the environment with
eggs. Adult males tend to remain on the host for several matings. It is often easier to identify the species
of adult male specimens versus adult females due to the excessive engorgement of the females (see
text). (A) Engorged females lay eggs off the host in long grass. Eggs hatch when conditions are favourable
(that is, suitable temperature and level of humidity). (B) Larvae emerge and cluster on grass to infect the
first host (C). (D) Engorged larvae moult off the host to form the nymph stage. (E) Nymphs attach to
the next available host which may be a different species of mammal or bird. (F) Engorged nymphs moult
off the host and emerge as adult ticks. (G) Adult male and female ticks mate and attach to the next host.
The female engorges and detaches into the environment where she lays her eggs.

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