Phenotypic resistance to ivermectin in Hyalomma anatolicum populations from north-western state of Punjab, India.

Hyalomma anatolicum is a multi-host ixodid tick species that significantly contributes to the spread of pathogens, posing economic and health challenges for livestock populations. This study assessed the acaricide resistance status to ivermectin in H. anatolicum field populations from north-western state of Punjab, India by larval immersion test. Dose-mortality response was analysed using probit transformation of percent mortality and logarithmically transformed drug concentrations, and lethal concentration (LC50, LC90 and LC99) and resistance ratio values were determined. Bioassay results revealed resistance status against ivermectin in all studied field isolates with RR50 values ranging from 8.87 to 95.22. The maximum value was recorded in MKS (RR50 = 95.22), followed by FKA (RR50 = 48.78) and minimum in BNN isolate (RR50 = 8.87). The findings highlight a concerning trend of resistance development in field isolates of multi-host cattle tick from Punjab state and thereby emphasizing the need for resistance management strategies, including integrated tick management practices, rotational use of acaricides and adoption of alternative control measures.