Effect Of The Type And Dosage Of Acaricides On Re-Infestation Rates Of Ticks On Field-Grazing Cattle

ABSTRACT Tick infestation of cattle remains one of the major constraints to cattle production in Africa. Reduction of ticks should, therefore, enhance cattle production which is critically needed to ensure economic and food security. In the current study, 59 farmers were interviewed about the types of pesticides available for routine pest control on their farms. There were different types of acaricides commercially available for use in Ghana and the addition of new types from different companies is growing rapidly. The results also revealed the three leading types of acaricides; Milbitraz, Eraditick, and Amiraz, which were popular among farmers. There was overwhelming evidence of the uncontrolled use of different acaricides against ticks. Tick species were most likely exposed to the commonly used active ingredients in acaricides namely, amitraz, representing the amidine group and pour-ons from the cypermethrin group. The results also showed that Eraditick was the most preferred among amitraz-based formulations, representing the predominant acaricides on all cattle farms. Overall, farmers in Ghana used different methods of tick control. However, strategic acaricide application, via spraying with the knapsack sprayer was the preferred method for resource-poor farmers. The strengths (toxicity) of the most commonly used active ingredients of products were tested in a dose-dependent fashion against ticks feeding on cattle by comparing 1) the number of dead ticks and 2) time of re-infestation. Generally, the killing activity of the prototypical non-systemic emulsifiable concentrate was thrice faster than the cypermethrin group referred to as the “pour-ons.” Specifically, spraying with Eraditick resulted in clearance of >50% of the population of targeted ticks within 24 hours as compared with 72 hours required by either Cypertop or Zerotick. There was no difference in the toxicity between the use of higher concentrations and the recommended dose of the manufacturer (p=0.814) because increasing ix the dosage of acaricides did not result in a corresponding increase in the number of dead ticks. Notably, 70% of farmers used 1-3 types of acaricides, in rotation or simultaneously. However, complete tick clearance was not achievable even with a combination of two or more amitraz-based formulations. From the current study, the re-infestation rate of tick species ranged from 10 ticks/day to 30 ticks/day. Regardless of the number of types and dosage of different non-systemic acaricides tested, the re-infestation time of ticks to cattle occurred within 7 days, post-application. On the contrary, the results have demonstrated the possibility of combining the acaricidal effects of the emulsifiable concentrate-based acaricide (Eraditick) with pour-on based (Cypertop) to improve toxicity in tick populations. This combination was able to kill >80% of tick species as compared to 50-60% using the traditional acaricides alone. It equally achieved a near-zero clearance of ticks within 6 days of application that was impossible with the other alternative pairings. Notably, this chemical association consistently cleared all ticks from different groups of animals and delayed re-infestation with new ticks for over 14 days. The huge difference in the acaricidal strength has a significant effect on both the time it takes to clear the existing ticks and the re-infestation rates of new ticks to the previously treated cattle. Altogether, results from the current study are big findings that could transform the way we control livestock ticks. This could reduce the cost of producing animals and improve livelihoods by reducing poverty among cattle farmers.