Susceptibility of some East African Strains ofRhipicephalus appendiculatusto Cholinesterase Inhibiting Acaricides

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Abstract
On the basis of dosis mortality tests on larvae of Rhipicephalus appendiculatus in acaricide impregnated filter packets provisional baseline data were determined to enable detection of changes in susceptibility to cholinesterase inhibiting acaricides. Homogeneous resistant material from three resistant strains was tested simultaneously with susceptible strains from Muguga (Kenya), Mbeya and Mwanza (Tanzania). For each strain the concentration of active material dissolved in oil, able to produce mortality response in half the population (LC50 value) was determined. The LC50 values obtained for both the susceptible and organochlorine resistant strains were almost identical and in accordance with data from workers in Australia obtained with susceptible Boophilus microplus. These data for ten acaricides, bromophos-ethyl, carbaryl, carbophenothion, chlorfenvinphos, chlorpyriphos, coumaphos, diazinon, dimethoate, dioxathion and quintiofos characterising and revealing possible types of resistance are of major practical importance in view of increasing use of these compounds in East Africa and elsewhere, and the spread of confirmed cases of organochlorine resistance in East Africa.