Se. Randolph et K. Storey, Impact of microclimate on immature tick-rodent host interactions (Acari : Ixodidae): Implications for parasite transmission, J MED ENT, 36(6), 1999, pp. 741-748
Rodents play a significant role in enzootic cycles of tick-borne pathogens,
notably, in the northern hemisphere, tick-borne encephalitis virus and Lym
e borreliosis spirochaetes. The relative numbers of nymphal and larval tick
s feeding on rodents are crucial variables in determining the probability o
f rodent infection and the degree of amplification of infection prevalence
in the tick population. Manipulation of the microclimate within quasinatura
l experimental arenas revealed that under increasingly dry conditions the n
umbers of unfed nymphal Ixodes ricinus L. questing in upper layers of the h
erbage decreased, whereas the rate of fat use and the numbers of nymphs fee
ding on small rodents, both increased. This is consistent with nymphs desce
nding to the moist lower vegetation layers for water replenishment, where t
hey would come into contact with small hosts. Very few larvae quested or fe
d on rodents under the dry conditions, but many more did so once the humidi
ty increased, suggesting that larvae escape desiccation by becoming quiesce
nt. The ratio of larvae to nymphs feeding on rodents thus increases with in
creasing humidity, contributing to the seasonal and geographical variation
in disease transmission dynamics.