Validation of the in-vitro efficacy of selected illicit pesticides used for controlling acaricide resistant ticks in Western Uganda
Mutesasira, Jesse Mukisa
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Tick and Tick-borne Diseases (TBD) cause serious economical losses to livestock production in Uganda. Various strategies are used in tick control but acaricides are the most common. Due to factors such as wrong dilution, poor application and irrational use of acaricides, multi-acaricide resistance has emerged in central and western Uganda. As a result farmers are reported to be using crop pesticides where acaricides have failed to kill ticks. A cross sectional study was carried out to screen ticks for multi-acaricide resistance, determine their susceptibility to selected agro chemicals. It also involved determination of the LC50 and LC95 of these agrochemicals in order to validate their efficacy in multi-acaricide resistant tick control. Ticks that were resistant to at least two of the classes of acaricides were considered in the study. Rhipicephalus appendiculatus and Rhipicephalus (Boophilus) decoloratus ticks were identified from the total ticks collected from Kabarole and Kiruhura districts in western Uganda to be used for Larval Pack Test (LPT) method. The Multi Acaricide Resistant Ticks were then tested with X01, found to contain Acetaprimid 30% w/v and X02 containing Metrifonate 45% w/v for tick susceptibility. Having shown susceptibility, serial dilutions were done so as to determine the LC50 and LC95. The lowest concentration found to be killing the ticks was at 0.03mg/ml for X01 and 4.5 x 10-39mg/ml for X02. The LC50 for XO1 was found to be 0.512mg/ml for Rhipicephalus appendiculatus and the mean LC50 for Rhipicephalus (Boophilus) appendiculatus was 3.92 x 10-16mg/ml. The LC95 was 18.44mg/ml and 0.04mg/ml for X01 and X02, respectively. The Diagnostic Doses (DD) for X01 and X02 for the tick larvae were 36.87mg/ml and 0.04mg/ml respectively with that of X01 being much higher than the DDs of the pre existing acaricides at recommended dosages, the reverse was found for X02. This calls for a need to rationally use the pre existing acaricides but in a rational manner instead of use of the agrochemicals for tick control which may posse greater toxicity risks which are not yet known.