STATUS OF ACETYLCHOLINESTERASE MEDIATED ORGANOPHOSPHATE RESISTANCE IN CATTLE TICK, RHIPICEPHALUS MICROPLUS (ACARI: IXODIDAE)

Ticks, the haematophagus ectoparasites with worldwide distribution especially in tropical and sub-tropical regions, severely affect health and productivity of animals. Different classes of chemical acaricides like organochlorines, organophosphates, formamidines, synthetic pyrethroids and macrocyclic lactones are currently used for controlling the tick infestations. The continuous and indiscriminate treatments often leads to acaricide resistance, environmental pollution and residues in meat and milk products. Organophosphate (OP) compounds were initially introduced as a replacement to organochlorines as they were non-persistent and did not accumulate in the fat tissues. The global scenario of OP resistance development in cattle tick, Rhipicephalus microplus has been summarized in the present review. The various resistance mechanisms against OPs in R. microplus include target site modification in the acetylcholinesterase (AChE), and carboxylesterase (CE) gene, as well as metabolic detoxification.