Accumulation and persistence of flea larvicidal activity in the immediate environment of cats treated with imidacloprid

To investigate the persistence of flea larvicidal activity in the immediate environment of cats treated with imidacloprid, eggs of the cat flea Ctenoc ephalides fells fells Bouche (Siphonaptera: Pulicidae), from untreated dono r cats, were incubated on samples of fleece blanket taken from the floor of cages used by treated or untreated cats for a total of 10 or 20 6-h period s over 2-4 weeks, respectively. Sufficient imidacloprid accumulated during these periods to reduce the emergence of adult fleas by 94.7-97.6% when the blankets were tested after 18 weeks' storage at room temperature. A typica l laundry procedure (washing with detergent at 50 degreesC and low temperat ure tumble drying) removed this biological activity. Unwashed control blank ets did not support the flea life-cycle as effectively as washed blankets o r a sand substrate.