Ecology of the common marsupial tick (Ixodes tasmani Neumann) (Acarina : Ixodidae), in eastern Australia

Abstract

Ixodes tasmani is one of the most common and widespread of the Australian species of Ixodes and a vector of zoonotic rickettsial diseases. The tick was reared successfully in the laboratory; the entire life cycle was completed in 4 months. A diurnal rhythm of detachment from captive hosts (laboratory Rattus norvegicus) was observed for all stages and, combined with other evidence, suggests that I. tasmani is nidicolous. The prevalence and intensity of tick infestation on wild-caught, common brushtail possums (Trichosurus vulpecula), was least during the summer months. To investigate questing activity, laboratory-reared nymphs were held in enclosures in one sheltered (tree hollows) and three exposed (vegetation) microhabitats. Questing was continuous but at low intensity in tree hollows, and nocturnal and at an increased (higher) intensity in vegetation. The observed questing activity appeared to maximise host contact with T. vulpecula, which is nocturnal but retires by day to tree hollows. Field and laboratory observations suggest that the risk for humans of tick-bite from I. tasmani and consequent transmission of zoonotic diseases may be low compared with the risk from other tick species.