The objective of the study was to evaluate through in vivo test, the efficacy and residual period of protection of 10% fipronil "top spot" for dogs with different Ctenocephalides felis felis burdens of infestations. For this, 24 Beagles were used, divided into four groups of six dogs each. The dogs of the control groups I and II were not treated, while the dogs of the treated groups I e II were treated with the formulation of 10% fipronil "top spot". The dogs of the control group I and treated group I were infested with 100 unfed C. felis felis and dogs of group control II and treated II one were infested with 300 unfed C. felis felis each. Infestations were performed on days -2, +5, +12, +19, +26, +33 and +40, and on days +2, +7, +14, +21, +28, +35 and +42 fleas were mechanical removed and counted for evaluation. Efficacy for treated group I on days +2, +7, +14, +21, +28, +35 and +42 was respectively 99.36%, 99.73%, 99.48%, 99.00%, 74.00%, 99.75%, 95.06% and 67.62%. The efficacy for the treated group II, evaluated on the same days, was respectively 100%, 100%, 100%, 100%, 99.91, 95.60% and 68.55%. Fipronil was effective in eliminating fleas on dogs until day +35. The statistical comparisons of the mean living fleas between control I group and treated I one showed significant differences (p≤0.05) for the challenges on all experimental days after treatment. Control II group and treated II one also showed significant differences (p≤0.05) for the challenges on all experimental days after treatment. Statistical analysis between treated group I and II showed no significant difference (p≥0.05) between the challenges on all experimental days. The challenges were finished on day 42, when the effectiveness of fipronil in treated groups I and II were lower than 70%. The tested product was effective in eliminating fleas on dogs until day + 35 with no more residual effect of protection when the animals were reinfested. There was no difference in efficacy levels between the groups infested with 100 and 300 specimens of C. felis felis throughout the experimental period
Phenylpyrazol; chemical control; fleas; Ctenocephalides felis felis; dogs.
