Deltamethrin resistance in Rhipicephalus sanguineus and Rhipicephalus (Boophilus) microplus tick population in Kerala

The study evaluated deltamethrin resistance in Rhipicephalus sanguineus and Rhipicephalus (Boophilus) microplus tick populations of Kerala in India, using larval packet test (LPT). Dose response data were analysed by the probit method, the LC50 and LC95 of deltamethrin against ticks were determined by applying regression equation analysis to the probit-transformed data of mortality. In R. sanguineus, 50 per cent of isolates were found resistant at discriminating dose (600 ppm) by larval packet test. The p value obtained upon regression analysis was < 0.05 and was considered as significant. A majority of R. (B.) microplus were found to be susceptible to deltamethrin. However, these susceptible isolates survived doses which were twice the recommended doses (1.25 ppm – 100 ppm). The p value of isolates except isolate 1 and 5 were < 0.05 and statistically significant. The results highlight acaricide resistance to be one of the reasons for the alarming prevalence of tick-borne haemoparasites in Kerala and demand urgent interventions to ameliorate the resistance by alternate control strategies.