Systemic activity of a benzimidazoline compound in cattle against ticks and biting flies

Abstract

A benzimidazoline compound [4-nitro-2-(1,1,2,2-tetrafluoroethyl)-6-(trifluoromethyl)-1H-benzimidazol-2-, 01, sodium salt] referred to as EL-979 showed systemic acaricidal and insecticidal activity in cattle against 2 tick species, Amblyomma maculatum (Gulf Coast tick) and Dermacentor variabilis (American Dog tick) and adult Stomoxys calcitrans (stable flies). Larvae of black blow fly ( Phormia regina) were fed serum collected from treated calves. A complete kill of larvae was obtained with a serum level of 3 parts per million (p.p.m.) of EL-979. Intravenous infusion at the rate of 0.25 mg kg −1 per day for 12 days provided a concentration of EL-979 in the blood of approximately 5 p.p.m. In A. maculatum this blood level prevented feeding in larvae and molting in nymphs, reduced numbers of females successfully feeding and prevented larvae production. D. variabilis adults were not as susceptible to a blood level of 5 p.p.m., but the number of feeding larvae and molting nymphs were reduced. Complete mortality of adult S. calcitrans occurred with repeated feedings of a 5 p.p.m. blood level. Fly control of 80% was found with 2.3 p.p.m. multiple feeds. Calf sera with a concentration range of 16–20 p.p.m. killed all flies which took a single feeding.