Cold-stress response of engorged females of Rhipicephalus sanguineus.

We investigated the effect of prolonged exposure to low temperature on engorged females of Rhipicephalus sanguineus. Five groups of two females (F1-F5) were maintained at 8 ± 2°C, 70 ± 10% RH, and 24 h scotophase, for 15, 30, 45, 60 and 75 days. One group was maintained in the incubator (26 ± 1°C, 70 ± 10% RH, and 24 h scotophase) as control. The results show that egg hatch rate, longevity and reproductive fitness of engorged females of R. sanguineus are negatively correlated with the duration of exposure to low temperature, whereas preoviposition period was positively correlated with exposure to the cold. This shows that the engorged female ticks are sensitive to prolonged exposure to low temperature, and it may explain why females of this tick species are not reproductively active during winter. Our results confirm that temperature is a major limiting factor for the establishment of stable R. sanguineus populations in cold temperate regions of Europe.