Influence of sheep breed and application site on the efficacy of a flumethrin pour-on formulation against ticks.

The objectives of this study were to determine the influence of application site and sheep breed on the efficacy of a flumethrin (1% m/v) solution for the control of 'bont'-legged (Hyalomma spp.) and red-legged ticks (Rhipicephalus evertsi evertsi). This study was conducted from November 1996 to February 1997 on 3 farms in the southwestern Free State Province. Two trials were conducted on Dorper sheep and 2 on Merino sheep. For each specific application 30 sheep were selected and allocated to 3 groups of 10 animals each using randomisation through minimisation, with pre-treatment total tick count as only criterion. Groups consisted of an untreated control group, a group treated with 3 ml of a flumethrin (1% m/v) solution applied only to the anogenital region, and a group treated at a dose rate of 1 mf flumethrin (1% m/v)/5 kg host body mass. The total dose volume for animals in the last group was divided into 3 equal parts and applied to the brisket/axillae, groin and anogenital regions respectively. Animals grazed under extensive farming conditions and were infested by ticks that occurred naturally in the environment. Ticks were counted and removed weekly over a 6-week period. In all 4 trials, Rhipicephalus e. evertsi was the dominant tick species, followed, in 3 of the trials, by Hyalomma spp. Efficacy (%) of control against ticks for Dorper sheep, treated only on the anogenital region, was variable, ranging between 29.5 and 97%. In Merino sheep the efficacy values ranged between 23.1 and 90 %. The site-spcific (anogenital region) efficacy of control against ticks infesting Merino sheep was in general 100% or almost 100%. In Dorper sheep the efficacy values were >80 % for 3-5 weeks. The efficacy (%) of control against ticks for sheep treated on the brisket/axillae, groin and anogenital regions was always higher compared to sheep treated only on the anogenital region. In Dorper sheep, efficacy of control was >80 % for up to 4 weeks and in Merino sheep >80 % for 6 weeks.