ENZYMATIC DETOXIFICATION MEDIATED DELTAMETHRIN RESISTANCE IN HYALOMMA ANATOLICUM (ACARI: IXODIDAE) POPULATIONS OF WESTERN PUNJAB

Resistance status against deltamethrin was assessed in Hyalomma anatolicum ticks collected from seven districts of western zone, Punjab, India using Larval Packet Test (LPT). The regression graphs of probit mortality of larval ticks plotted against log values of increasing concentrations of deltamethrin were utilized for the determination of slope of mortality, lethal concentration for 50% (LC50) and 95% (LC95) with 95% confidence interval (CI), and resistance ratios (RR50 and RR95). The LC50 and LC95 values ranged from 2.36–18.72 and 19.28–59.9 ppm in various field isolates whereas, in susceptible ticks (Fazilka isolate) were 1.47 and 9.33 ppm, respectively. The values of RR50 and RR95 ranged from 1.60 to 12.73 and 2.06 to 6.42, respectively, confirming the resistance status of all field populations. On the basis of RR50 values, level I resistance status was recorded in three field isolates and level II in four isolates. Esterase profile of the tick larval extracts using native PAGE, revealed 5 bands of esterase activity designated EST-1 to EST-5. Inhibitory tests recognized EST-1 and EST-2 as acetylcholine esterases, EST-3, EST-4 and EST-5 as carboxylesterases. Quantitative analysis of general esterase activity revealed a range of 3.249 ± 0.31 to 4.523 ± 0.59 and 1.747 ± 0.11 to 2.296 ± 0.20 µmol/min/mg protein for α and β-esterase activity, respectively in different field isolates whereas, glutathione-S-transferase (GST) activity was in range of 0.0127 ± 0.0007 to 0.0289 ± 0.0017 mM/mg/min. A strong correlation was recorded between the resistance ratios against deltamethrin and enzyme ratios (∝- esterase and GST) of various field isolates of H. anatolicum indicating their possible role in resistance development.