title: First report of ivermectin resistance in field populations of Rhipicephalus (Boophilus) microplus (Acari: Ixodidae) in Punjab districts of India.
abstract: The larval immersion test (LIT) was used on the progenies of Rhipicephalus (Boophilus) microplus collected from four districts of the Punjab state, India to test the resistance to ivermectin. The regression graphs of probit mortality of larval ticks plotted against log values of increasing concentrations of ivermectin were utilized for the determination of slope of mortality, lethal concentration for 50%(LC50), 95%(LC95), resistance ratios (RR50, RR95) and the resistance levels (RL). Values of the coefficient of determination (R(2)) for LIT ranged from 0.900 to 0.978, and the RR50 and RR95 values against ivermectin ranged from 2.97 to 8.85 and 2.42 to 8.47, respectively, indicating resistance status in all field isolates. On the basis of RR values, three field isolates (BAT, GUR, HOS) showed level II, whereas PTK isolate showed presence of level I resistance status against ivermectin. This appears to be the first report of ivermectin resistance in R. (B.) microplus from Punjab, India.
authors.affiliation: Department of Veterinary Parasitology, College of Veterinary Science, Guru Angad Dev Veterinary and Animal Sciences University, Ludhiana 141004, India. Electronic address: nirbhayksingh@yahoo.co.in.
authors.forename: Nirbhay Kumar
authors.initials: NK
authors.lastname: Singh
authors.affiliation: Department of Veterinary Parasitology, College of Veterinary Science, Guru Angad Dev Veterinary and Animal Sciences University, Ludhiana 141004, India.
authors.forename: Harkirat
authors.initials: H
authors.lastname: Singh
authors.affiliation: Department of Veterinary Parasitology, College of Veterinary Science, Guru Angad Dev Veterinary and Animal Sciences University, Ludhiana 141004, India.
authors.lastname: Jyoti
authors.affiliation: Department of Veterinary Parasitology, College of Veterinary Science, Guru Angad Dev Veterinary and Animal Sciences University, Ludhiana 141004, India.
authors.forename: Mranalini
authors.initials: M
authors.lastname: Prerna
authors.affiliation: Department of Veterinary Parasitology, College of Veterinary Science, Guru Angad Dev Veterinary and Animal Sciences University, Ludhiana 141004, India.
authors.forename: Shitanshu S
authors.initials: SS
authors.lastname: Rath
mesh_terms: D000818:Animals; D000977:Antiparasitic Agents / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004351:Drug Resistance; D005260:Female; D007194:India; D007559:Ivermectin / Q000494:pharmacology*; D048494:Rhipicephalus / Q000187:drug effects*
chemical_list: D000977:Antiparasitic Agents; D007559:Ivermectin
keywords: Ivermectin; Punjab; Resistance; Rhipicephalus (Boophilus) microplus