The role of pheasants (Phasianus colchicus) as hosts for ticks (Ixodes ricinus) and Lyme disease spirochaetes (Borrelia burgdorferi) in southern England

The quantitative role of pheasants, Phasianus colchicus, as hosts for the tick, Ixodes ricinus, the principal vector of the Lyme disease spirochaete, Borrelia burgdorferi, was examined in a British woodland focus of Lyme borreliosis. Questing ticks exhibited a unimodal pattern of activity in spring and summer, but some nymphs and adults fed on hosts through the autumn and winter. Pheasants supported mainly nymphal ticks and peak infestation levels occurred during April, when the median burdens were 43.0 nymphs/male and 4.5 nymphs/female. Calculations of the tick carrying capacity of pheasants compared with that of wood mice, Apodemus sylvaticus, bank voles, Clethrionomys glareolus, and grey squirrels, Sciurus carolinensis, revealed that wood mice fed the most larvae throughout the year, with squirrels feeding important numbers in summer, and that pheasants and squirrels fed large numbers of nymphs during spring-autumn. These data suggest that pheasants are important in maintaining the transmission of Lyme disease spirochaetes in lowland woods in the UK. The exclusion of roe deer, Capreolus capreolus, from woodland by fencing remained an effective means of reducing tick densities despite the fact that pheasants had unrestricted access to such areas.