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Title: Effects of Ivermectin on the Susceptibility of Culicoides Sonorensis (Diptera: Ceratopogonidae) to Bluetongue and Epizootic Hemorrhagic Disease Viruses

Author
item REEVES, WILL
item NOL, PAULINE - USDA VETERINARY SERVICE
item MILLER, MYRNA
item JONES, GUINEVERE - UNIVERSITY OF WYOMING

Submitted to: Journal of Vector Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/3/2009
Publication Date: 6/8/2009
Citation: Reeves, W.K., Nol, P., Miller, M.M., Jones, G.Z. 2009. Effects of Ivermectin on the Susceptibility of Culicoides Sonorensis (Diptera: Ceratopogonidae) to Bluetongue and Epizootic Hemorrhagic Disease Viruses. Journal of Vector Ecology. Vol 34: 161-163.

Interpretive Summary: Ivermectin is one of the most frequently used antiparasitic drugs in the livestock industry. It is toxic to insects and other invertebrates. The mortality of biting midgesthat feed on livestock treated with ivermectin ranges from 0% to almost 99%. There is no data on the effects of ivermectin on the susceptibility of biting midges to bluetongue or epizootic hemorrhagic disease viruses. We drew blood from sheep and elk and then injected same sheep with 400 µg/kg ivermectin and elk with 200 µg/kg of ivermectin and an anti-liver fluke drug. A second blood draw was made 24 hours post treatment. We fed control and treated blood mixed with bluetongue or epizootic hemorrhagic disease viruses to biting midges, held them for 12 days, and ascertained viral infection rates. Treating sheep with 400 µg/kg ivermectin reduced infection rate of biting midges with bluetongue virus by 50%, however treating elk with 200 µg/kg of ivermectin and an anti-liver fluke drug had no effect on epizootic hemorrhagic disease viruse infection rate. We also tested the toxicity of 200 µg/kg ivermectin treatment in ponies to biting midges. There was no significant control of biting midges with this treatment.

Technical Abstract: Ivermectin is one of the most frequently used antiparasitic drugs in the livestock industry. It is toxic to insects, because it can hyperpolarize their nerve and muscle cells and increases cellular membrane permeability to chloride ions, which leads to muscular paralysis. The mortality of Culicoides spp. feeding on livestock treated with ivermectin ranges from 0% to almost 99%. There is no data on the effects of ivermectin on the susceptibility of Culicoides sonorensis to bluetongue or epizootic hemorrhagic disease viruses. We drew blood from sheep and elk and then injected sheep with 400 µg/kg ivermectin and elk with 200 µg/kg of ivermectin and clorsulon. A second blood draw was made 24 hours post treatment. We fed control and treated blood mixed with bluetongue or epizootic hemorrhagic disease viruses to midges, held them for 12 days, and ascertained infection rates. Treating sheep with 400 µg/kg ivermectin reduced infection rate of C. sonorensis with BTV by 50%, however treating elk with 200 µg/kg of ivermectin and clorsulon had no effect on EHDV infection rate. We also tested the toxicity of 200 µg/kg ivermectin treatment in ponies to C. sonorensis. There was no significant control of C. sonorensis with this treatment.