Acaricide resistance in Rhipicephalus appendiculatus Neumann, Amblyomma Variegatum (Fabricius) and Boophilus decoloratus (Koch) in Southern and Central Provinces of Zambia

Acaricide resistance tests were conducted on 14-21 days old larvae of Rhipicephalus appendiculatus Neumann, Amblyomma variegatum (Fabricius) and Boophilus decoloratus (Koch), using the Food and Agriculture Organization (FAO) Acaricide Resistance Test Kit, and acaricide test papers prepared locally according to the FAO method. Engorged female ticks for larval production were collected from different localities in the Southern and Central (including Lusaka) Provinces of Zambia. The lowest LC50(%) values obtained from sets of data for each tick species were used to calculate resistance factors (RF).The range of LC50(%) values for R. appendiculatus and for B. decoloratus in brackets using the FAO Kit were: cypermethrin, 0.025-0.30 (0.03-0.045), coumaphos, 0.13-0.60, dioxathion, 0.20-0.60 (0.35-0.60), diazinon, 0.03-0.13 (0.015-0.06) and dieldrin, 0.08-0.30. For local papers values were: cypermethrin, 0.026-0.260 (0.012-0.056), chlorfenvinphos, 0.02-0.08 (0.012-0.12), dioxathion, 0.062-0.47 (0.03-0.50) and deltamethrin, 0.005-0.015 (0.004-0.011). For A. variegatu/n values with the FAO Kit and values with local papers in brackets were: dioxathion, 0.15-0.26 (0.032-0.32), cypermethrin, 0.03-0.082 (0.01-0.084), dieldrin, 0.05-0.32 and chlorfenvinphos (0.011-0.052). These results indicated that cattle ticks in the Southern and Central Provinces of Zambia are developing resistance to acaricides. B. decoloratus in the commercial sector and R. appendiculatus in the traditional sector showed resistance to a number of acaricides whereas Amblyomma variegatum showed resistance to dieldrin and dioxathion. Boophilus decoloratus from the traditional sector were however, relatively susceptible. The observed pattern of resistance is attributed to a number of factors such as the frequency of acaricide application, cattle management and type of cattle and other agricultural and ecological factors.
Although cypermethrin and dioxathion were the only acaricides which were both in the FAO Kit and locally prepared test papers, results obtained showed some agreements between the two types of test papers. From the results, it is possible to identify resistance using local papers on the same lines as would be with the FAO papers.
Since chemical control of ticks is the most practical method of controlling ticks and tick-borne diseases in Zambia, the usage of acaricides should be carefully monitored to avoid development of multiple resistance in tick populations. Although locally prepared papers have their limitations, it is important to note that they may be a useful tool in enabling economically poor countries like Zambia to detect early resistance in ticks in the absence of the standardised FAO Resistance Test Kit. An integrated approach to tick control involving less use of acaricides is discussed.