Treatment of Trombicula autumnalis infestation in dogs and cats with a 0.25 per cent fipronil pump spray.

To evaluate the efficacy of fipronil in controlling trombiculid infestations, 18 dogs and three cats infested with Trombicula autumnalis larvae were treated monthly from examination to the end of the Trombicula season (range one to four months) with a 0.25 per cent fipronil spray applied to the whole body, with particular emphasis on the feet, face, ears, perineum and tail. No other antiparasite measures were used. Follow-up was by clinical examination and telephone interview until the end of the Trombicula season (range one to four months). No adverse effects were seen. Monthly treatment controlled trombiculids in 15 dogs. In two dogs localised pedal reinfestations were controlled with additional local application of fipronil to the feet every 14 days. In one dog therapy was of no benefit. In the three cats, treatment was initially effective, but generalised infestations recurred after seven to 10 days. Fipronil is a safe and effective treatment for trombiculid infestations in dogs. Residual activity lasts for 14 to 30 days. Further studies are required to examine the apparent short duration of efficacy in cats.