Esterase and glutathione S-transferase levels associated with synthetic pyrethroid resistance in Hyalomma anatolicum and Rhipicephalus microplus ticks from Punjab, India

Larval packet test was used for assessment of resistance status against cypermethrin and deltamethrin in Hyalomma anatolicum and Rhipicephalus microplus from various districts of Punjab (India). Among the various field isolates of H. anatolicum susceptible status was recorded against cypermethrin in all isolates, whereas against deltamethrin resistance status (level I-III) was recorded. In R. microplus lower resistance levels (I-II) were recorded against cypermethrin in comparison to deltamethrin (level I-IV). Quantitative analysis of general esterase activity revealed a range of 4.21 +/- 0.46 to 6.05 +/- 0.55 and 2.23 +/- 0.23 to 2.66 +/- 0.24 mu mol/min/mg protein for alpha- and beta-esterase activity, respectively, in different field isolates of H. anatolicum and the increase in comparison to susceptible was not significant (P > 0.05). In contrast to H. anatolicum, the a-and b-esterase activity in all field isolates (except Jalandhar) of R. microplus was higher (range of 3.89 +/- 0.26 to 10.85 +/- 0.47 and 1.75 +/- 0.08 to 5.87 +/- 0.29 lmol/min/mg protein, respectively) (P < 0.001). The glutathione-S-transferase (GST) activity in field isolates of H. anatolicum and R. microplus was in the range of 0.01 +/- 0.001 to 0.03 +/- 0.001 and 0.02 +/- 0.0003 to 0.03 +/- 0.001 mM/mg/min. The enzyme ratios (alpha-and beta-esterase and GST) and RR95 against deltamethrin of H. anatolicum isolates were correlated (P < 0.05), whereas in R. microplus only alpha-and beta-esterase and RR50 against deltamethrin were correlated (P < 0.05).