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  Development Cycle

The common castor-bean tick (Ixodes ricinus) spends most of its life free-living on the ground or among vegetation.

The ticks are characterized by a comparatively long life cycle, lasting several years, during which the infecting virus may be maintained from one developmental stage of the tick to the next. Hence ticks act as highly efficient reservoirs of flaviviruses. Many tick-borne flaviviruses are transmitted vertically, from adult to offspring, although the frequency is too low to maintain the viruses solely in the tick population. Instead, the survival of tick-borne flaviviruses is dependent on horizontal transmission, both from an infected tick to a susceptible vertebrate host and from an infected vertebrate to uninfected ticks feeding on the animal.

Copulation usually takes place on a host prior to blood feeding. Following copulation, the female spends six to eleven days feeding on blood and during subsequent months deposits 500 to 5,000 eggs in several places in the loose top layer of the soil. Several weeks later, larvae measuring 0.61.0mm hatch from the eggs. Unlike the subsequent developmental stages (nymph and imago) larvae only have three pairs of legs, no stigmata, and no sexual openings.

In each stage of development (larva, nymph, and imago) ticks have to feed at least once on a vertebrate host before they can develop into the next stage. Male ticks do not feed on blood, but take only a small amount of tissue fluid during a short feed. Larvae feed on
a host for two to five days before they drop off and moult into nymphs. These feed on a vertebrate host again for two to seven days and metamorphose into adults (imagos).

The duration of the developmental cycle of one tick generation from egg to oviposition by a fertilized female, varies according to the literature between six months and eight years. The average time in Central Europe is thought to be two years, although in adverse environmental conditions each stage of development may take longer.


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