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Title: Suppression of mosquito (Diptera: Culicidae) and black fly (Diptera: Simuliidae) blood feeding from hereford cattle and ponies treated with permethrin

item Schmidtmann, Edward
item Bobian, Ronald

Submitted to: Journal of Medical Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/1/2001
Publication Date: 9/1/2001
Citation: Schmidtmann, E.T., J. Lloyd, R.J. Bobian, R. Kumar, J.W. Waggoner, W.J. Tabachnick,and D. Legg. 2001. Suppression of mosquito (Diptera: Culicidae) and black fly (Diptera: Simuliidae) blood feeding from hereford cattle and ponies treated with permethrin. Journal of Medical Entomology. 38(5):728-734.

Interpretive Summary: We tested the repellency of several commercially available synthetic pyrethroid insecticides against the blood-feeding of mosquitoes and black flies from cattle and ponies. The products tested, which contained permethrin as the active ingredient, are commonly used as insecticides and have U.S. registrations for use on domestic livestock. We treated animals and then compared the blood-feeding rates of insects between treated and non-treated animals at selected times after treatment. The results show that blood-feeding by mosquitoes was reduced by 79 - 88 % after four days, and 61 - 68 % after 11 days. Blood feeding by black flies was suppressed from 96 -99 % after 4 days and 30 - 87% after 11 days. Similar high levels of repellency were found when ponies were treated with a wipe-on formulation. Thus the data show that the synthetic pyrethroid insecticide permethrin provides effective protection against the blood-feeding of western species of mosquitoes and black flies for up to a week after treatment. We further estimated the benefits of using synthetic pyrethroid treatments to protect animals from insects infected with a pathogen using a predictive model that was based on 1) levels of blood feeding, 2) insect infection rates and 3) levels of repellency. The model indicates that treatment with permethrin, and possibly other synthetic pyrethroid products, can be an effective method for helping to protect livestock from pathogenic viruses carried by insects.

Technical Abstract: The blood-feeding of mosquitoes and black flies from Hereford cattle and ponies treated with commercial formulations of permethrin was evaluated using an animal enclosure trap sample system that allowed comparison of insect blood-feeding levels between treated and non-treated animals. Blood-feeding of both Aedes dorsalis and A. melanimon from heifers treated with pour-on concentrate and whole body spray treatments was reduced significantly by 79 % and 88 % at four days post-treatment, with apparent but not significant reductions of 61 % and 68 % at 11 days post-treatment. Black fly, Simulium bivittatum and S. griseum, blood feeding was reduced significantly by 96 % and 99 % at four days post-treatment, but apparent reductions of 30 % and 87 % at 11 days post-treatment were not significant. Blood feeding of S. bivittatum from ponies treated with a permethrin fly wipe was reduced significantly by 98 % and 99 % at one and seven days post-treatment, respectively. No evidence of treatment-induced mortality was observed for recently blood-fed female mosquitoes or black flies captured from treated animals and held for 24 h. The potential benefit of using permethrin to protect livestock from insect-transmitted pathogens was estimated with a model based on level of host attack, pathogen infection rate in the vector, and suppression of blood feeding. Suppression of blood-feeding by 90 % can be expected to prevent the exposure of a host to a pathogen for up to10 days at 1,000 insect feedings per day when the vector population infection rate is one insect per 1,000. If insect feedings are lower (100 per day) and the insect infection rate remains at one per 1,000, protection can be expected for 100 days. In contrast, a 90 % suppression of blood-feeding will provide protection for less than one day at 1,000 feeding per day and a vector infection rate of one insect per 100.