Detection of ivermectin resistance and its mitigation in Rhipicephalus (Boophilus) microplus of Jammu region
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Date
2022-01-25
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Sher-e-Kashmir University of Agricultural Sciences & Technology of Jammu (J&K)
Abstract
Status of ivermectin resistance was studied in 16 isolates of Rhipicephalus (Boophilus) microplus collected from 7 districts of Jammu region using Larval Immersion Test (LIT). The regression graphs of probit mortality of tick larvae plotted against log values of concentrations of ivermectin were utilized for the determination of slope mortality, lethal concentrations (LC50 and LC95) and resistance factor (RF). Based on the RF values obtained, resistance level was categorized as I, II, III and IV. Out of these 16 isolates examined, 15 were found resistant against ivermectin. Level II resistance was detected in eleven isolates, whereas four isolates (Doda, Sumbli, Kishtwar and Bhaderwah) exhibited level I resistance. Only one isolate (Padder) was found susceptible. Effect of two (MK-571 and Cyclosporin-A) ATP-binding cassette (ABC) transport inhibitors on the efficacy of ivermectin against R. (B.) microplus was studied. Pre-exposure to a single pre-determined sub-lethal concentration of these two synergists has led to reduction in LC50 values of ivermectin in different field isolates of R. (B.) microplus. MK-571 showed the highest increase in toxicity against ivermectin in the field isolates of R. (B.) microplus. The highest synergistic factors for MK-571 and Cyclosporin-A, were recorded in RS Pura isolate (2.51 and 1.78, respectively), whereas the lowest value was found for Kishtwar isolate (1.7 and 1.23, respectively). Efficacy of extracts (acetone, chloroform and ethanol) of hull of Juglans regia and rhizomes of Curcuma longa were tested against unfed larvae of R. (B.) microplus using LIT. For J. regia, based on LC50 values, the highest acaricidal activity was observed in ethanolic extract (LC50 of 1.43%) as compared to chloroform (1.52%) and acetone (1.22%). Among the three extracts of C. longa used, the highest acaricidal activity was observed in ethanolic extract with LC50, LC90, LC95 and LC99 values calculated as 2.43, 9.12, 13.26 and 26.77%, respectively.