A fast and efficient method has been developed and validated for the determination of fipronil in bovine plasma. Samples were subjected to solid-phase extraction (SPE) followed by reversed phase liquid chromatography (LC) separation, using acetonitrile/water (60:40 v/v) as the mobile phase with a flow rate of 1.0 mL/min and ultraviolet (UV) detection at 210 nm. Ethiprole was used as the internal standard (IS). The method was found to be linear over the range 5-500 ng/mL (r = 0.999). The limit of quantitation (LOQ) was validated at 5 ng/mL. The method was successfully applied to monitor plasma concentrations following subcutaneous administration of fipronil in cattle.

The objective of this study was to evaluate the efficacy of the synthetic pyrethroid alphamethrin in the control of Rhipicephalus sanguineus in dogs. In vitro tests with filter paper was done to nonengorged larvae, engorged larvae, nonengorged nymphs, engorged nymphs and nonengorged adults of R. sanguineus, given respectively a LC50 of 3,63; 4,79; 5,87; 10,01 and 11,19 ppm and a LC90 respectively of 13,17; 17,65; 29,37; 37,32 and 42,99 ppm. Different concentrations of alphamethrin was used in engorged females of R. sanguineus and the concentration of 300 ppm showed the most Reproductive Efficiency percentual (ER) (100%). In vivo tests in six dogs artificially infested with 500 nonengorged larvae, 100 nonengorged nymphs and 30 non engorged adults of R. sanguineus, given 86,2; 100 and 100% of mean efficacy respectively to larvae, nymphs and adults.