Footbath acaricide treatment to control cattle infestation by the tick Amblyomma variegatum

Previous studies have shown that about 90% of adult Amblyomma variegatum Fabricius (Acari: Ixodidae) picked up daily by grazing cattle are still attached to the inter-digital areas in the evening, when the animals return from pasture. It was therefore postulated that a targeted treatment, designed to kill the ticks attached to the feet, would limit infestation of the predilection sites. Footbaths filled with various pyrethroid formulations were used over 3 years, at the beginning of the rainy season (from mid-May to the end of July), to assess the efficacy of such a control method. It proved efficient in preventing the ticks from attaching to the predilection sites. Although five to 12 A. variegatum adults attached to each treated animal daily, and although the tick burden of the predilection sites of control cattle increased each day by four to 10 ticks, the average infestation of the predilection sites of treated cattle that were initially highly infested (over 100 ticks/animal) continuously decreased to reach a level of about 10-30 ticks/animal after 6-8 weeks of treatment. In herds with a lower initial tick burden (40-70 ticks/animal) this level was obtained within 2-3 weeks and the mean infestation subsequently remained consistently low. Footbath treatment carried out every other day during the adult peak infestation period should therefore greatly limit losses due to ticks. This method was appreciated by traditional livestock fanners, essentially because it is not time-consuming and because it requires only c. 200 mL aqueous formulation per animal at each passage. The cost of the acaricide needed to treat one animal during the peak infestation period was assessed at c. ¿ 0.20. This control method might also have an impact on some species of tsetse flies and mosquitoes, thereby contributing to trypanosomiasis and malaria control. (Résumé d'auteur