Antifeeding effect of several insecticidal formulations against Ctenocephalides felis on cats.

Evaluation of insecticidal activity of flea products is generally based on counting live fleas in the animal's coat 24 and 48 hours following artificial infestation. This approach, however, does not allow to specify whether the fleas have had the opportunity to bite and take a bloodmeal prior to their death. To address this question, 30 cats were alloted to six groups of five animals. Each cat was housed in a separate cage. At Day 0, each group of cats received a single treatment as follows: Group 1: spot-on application of imidacloprid: cats < 4 kg: 40 mg/cat, cats > or = 4 kg: 80 mg/cat (Advantage). Group 2: spot-on application of fipronil: 50 mg/cat (Frontline spot-on). Group 3: spray application of fipronil: 7.5 mg/kg b.w. (Frontline spray). Group 4: foam application of permethrin 40/60: 50 mg/kg b.w. (Defencat). Group 5: aerosol spray application of dichlorvos + fenitrothion: one second/kg b.w. (NuvanTop). Group 6: control group: cats were left untreated. One hour after treatment, each cat was infested with 50 unengorged young adult fleas, Ctenocephalides felis, deposited along the dorsal midline. One hour later, each cat was carefully combed using a fine-toothed comb (13 teeth/cm). Collected fleas were swatted to deteci blood in their abdomen. To the manufacturers respective product use instructions and efficacy claims, reeinfestations were made at Days 3, 7, 14 in all groups; at Days 21 and 30 in Groups 1, 2, 4, 6; at Days 35 and 42 in Groups 3 and 6. The cats were combed one hour after each reinfestation. The results indicate that the topical application of imidacloprid or fipronil does not prevent fleas from biting and feeding within the first hour after infestation prior to being killed while the topical application of dichlorvos/fenitrothion and permethrin let to a better than 80% decrease of the number of engorged fleas for three and seven days post treatment, respectively.