The extent of acaricide resistance in 1-, 2- and 3-host ticks on communally grazed cattle in the eastern region of the Eastern Cape Province, South Africa

Abstract

In order to determine the extent of acaricide resistance in the eastern region of the Eastern Cape Province 1-, 2- and 3-host ticks were collected from cattle at 59 dip-tanks over a period of 2 years. These ticks were tested for resistance against 3 compounds, namely amitraz, cypermethrin and chlorfenvinphos. The Shaw Larval Immersion Test detected emerging resistance to amitraz in Rhipicephalus (Boophilus) microplus at 2 dip-tanks and resistance at a 3rd. It also revealed resistance in this tick to cypermethrin at 1 dip-tank and emerging resistance to chlorfenvinphos at 8 dip-tanks and resistance at 2. Rhipicephalus evertsi evertsi was susceptible to amitraz and cypermethrin at all dip-tanks, but showed emerging resistance to chlorfenvinphos at 7 dip-tanks and resistance at 4. Rhipicephalus appendiculatus was susceptible to amitraz and chlorfenvinphos at all dip-tanks and demonstrated emerging resistance to cypermethrin at 1. With the exception of R. (B.) microplus, in which emerging resistance to amitraz was detected at 1 dip-tank by the Reproductive Estimate Test, all 3 tick species at all dip-tanks at which sufficient numbers of ticks had been collected were susceptible to the 3 acaracides in both the Egg Laying Test and the Reproductive Estimate Test. The localities at which acaricide resistance was recorded were mapped.