Page 71 - TBE_Book_V2_2019

Chapter 3: Transmission / Natural cycle

Adult females have 4 pairs of legs, and other shelters used by their hosts), and tend
spiracles, a genital aperture, and porose areas to be more host-specific. 7,14 Many Ixodes
14
on the dorsal surface of the basis capituli species are nidicolous. The main vectors of
(Figures 2a and 2b). Males have 4 pairs of legs, TBEV, I. ricinus and I. persulcatus are exophilic
the scutum covers the entire dorsal surface, and exceptional both in terms of the variety of
and hard sclerotized plates cover the ventral hosts they use as well as the habitats they
18
body surface of some species (Figures 2c and occupy.
2d). Ixodes males have the whole ventral view
covered with a total of 7 ventral plates. Host-finding behavior

Types of hard ticks Ixodid ticks’ host-seeking behavior is under
the control of different abiotic factors that
Ixodid ticks fall into 2 behavioral groups with differ according to the region. In temperate
respect to their habitat selection. Exophilic or and sub-polar regions, seasonal activity is
non-nidicolous ixodid ticks occur in the open mainly regulated by ambient temperature,
environment and are associated, depending changing photoperiod, and incident solar
on the species, with forests, savannahs, energy, and in the more temperate regions,
second-growth areas of scrub and brush, tick activity is often controlled by saturation
grassy meadows, semi-desert, or desert areas. deficit and relative humidity, with long-term
14
Such species are usually not host-specific. dry conditions being adverse for survival.
Nidicolous or endophilic ixodid ticks live in or Those species involved in the transmission of
near the nests of their hosts, are adapted to TBEV tend to quest passively or ambush their
highly specialized environments (crevices or hosts by climbing onto weeds, grasses, or

Figure 1

The life-cycle of Ixodes ricinus. The dotted arrows indicate potential transmission to humans. ©Nina Littwin

66