Vol. 12, Special Issue 8 (2023)

Author(s):
Jayalakshmi Jaliparthi, Udaya Kumar Manchukonda, Sreenivasamurthy G and Kalyani Putty

Abstract:
In Telangana, the ixodid tick Rhipicephalus microplus has developed resistance against synthetic pyrethroids, organophosphates and other acaricides. However, no cases of Amithraz resistance have been reported in this state despite of its heavy use. The modified Drummond Adult Immersion Test was utilized to determine the level of resistance to Amithraz in specimens collected from various areas of Telangana State, India. The regression graphs of probit mortality of Rhipicephalus microplus plotted against log values of Amithraz concentration was utilized for the determination of slope, lethal concentration 50%, 95% and resistance factor. The LC₅₀ and LC₉₅ values of adult immersion test against Amithraz was 116.5, 182.8, 94.56, 64.8, 100.2, 134.7 ppm and 655.1, 1353.5, 553.9, 1326.8, 1463.1, 1288.9 ppm in Rangareddy, Mahaboobnagar, Nizamabad, Warangal, Karimnagar, Khammam district isolates, respectively. Amithraz resistance was evaluated on the basis of a resistance factor (RF), which is the proportion of LC50 field ticks to susceptible ticks. In this study, all 6 isolates from different districts were susceptible to Amithraz showing resistance factor in the range of 0.39 to 1.1. The data generated in this study may be useful to the veterinarians of Telangana state in formulating effective tick control strategies.