Published online by Cambridge University Press: 10 July 2009
The results are presented of a survey of the resistance to acaricides of strains of economically important ticks from the cattle-raising areas of Kenya in 1970–75. Larval progeny of ticks collected in the field were subjected to an immersion test to determine their resistance status to toxaphene and dioxathion. The proportions of samples of the three major species shown to be resistant to or tolerant of toxaphene were Boophilus decoloratus (Koch) 99·3%, Rhipicephalus evertsi evertsi Neum. 77·3% and R. appendiculatus Neum. 62·5 %. A large proportion of the relatively few samples of R. pulchellus (Gerst.) were also resistant to toxaphene, but few resistant samples of Amblyomma variegatum (F.) and Haemaphysalis leachii leachii (Aud.) were collected, and only one sample of Hyalomma (H. marginatum rufipes Koch) was tolerant of toxaphene. None of these species was resistant to dioxathion. Organophosphorus resistance was noted in one species only, R. sanguineus (Latr.), collected from the suburbs of Nairobi.