Volume influence of a fipronil pour-on formulation on the effectiveness against Ctenocephalides felis felis and Rhipicephalus sanguineus in dogs
ABSTRACT. Silva D.D., Lambert M.M., Rocha C.N.C., Santos R.R., Magalhães V.S., Correia T.R., Grisi L. & Scott F.B. [Volume influence of a fipronil pour-on formulation on the effectiveness against Ctenocephalides felis felis and Rhipicephalus sanguineus in dogs.] Influência do volume de uma formulação pour-on de fipronil na eficácia sobre Ctenocephalides felis felis e Rhipicephalus sanguineus em cães. Revista Brasileira de Medicina Veterinária, 35(Supl.2):90-94, 2013. Programa de Pós-Graduação em Ciências Veterinárias, Instituto de Veterinária, Anexo 1, Universidade Federal Rural do Rio de Janeiro, BR 465 Km 7, Seropédica, RJ 23897-970, Brasil. E-mail: firstname.lastname@example.org This study aimed to evaluate the immediate and residual efficacy of different volumes of a pour-on formulation of fipronil in control of Ctenocephalides felis felis and Rhipicephalus sanguineus in dogs, keeping, however, the recommended dose of the active ingredient. For this purpose, 24 dogs were divided into four groups: control, which remained untreated and treated groups A, B and C, treated with pour-on solutions containing 10.7%, 5.3% and 1.8% fipronil, respectively. The volume of solution applied to the animals of groups A, B and C was respectively 1.34 ml, 2.68 ml and 5.36 ml, so that everyone received equivalent doses of the phenylpyrazole. Each dog was infested two days before treatment and weekly after the same 100 samples of non- fed adult C. felis felis and 50 non- fed adults of R. sanguineus, keeping for both, equal sex ratio . The evaluation of immediate efficacy occurred two days after treatment and residual efficacy assessments were performed weekly, always 48 hours after infestation. To this purpose, we proceeded to the removal and counting of fleas and ticks, by manual grooming and/or by “comb- test” method and the calculations of efficacy effected using the Abbott’s formula. The volume of 5.36 mL of fipronil solution applied in dogs offer protection against reinfestation by R. sanguineus superior to 90% for 28 days, higher than volumes of 1.34 ml and 2.68 ml, which were effective for a period of 21 days. Residual efficacy above 95% against C. felis felis was obtained up to 35 days for the three tested volumes. Despite fleacide efficacy less than 95% obtained in the 42º day after the treatment by all tested volumes, the 2.68 mL and 5.36 mL volumes presented superior than 1.34 ml volume. It is concluded that the increased volume of topically solution of fipronil applied in dogs, maintaining the recommended dose of the active ingredient, increased its residual efficacy against C. felis felis and R. sanguineus.