Losses in livestock production due to ectoparasite infestations exceed $2.26 billion annually. Over 50 species of ectoparasites infest cattle throughout the United States. The horn fly, Haematobia irritans (L.), is the most important and widespread of the five to six major pest species of pastured cattle in the southern region. Results from the examination of production traits from cattle under ectoparasite burdens have been variable, ranging from no effect to significant reductions in weight gains. Because of this inconsistency, specific physiological and nutritional responses in cattle infested or not infested with horn flies have been examined. Data have shown significant differences in nitrogen retention, blood cortisol concentrations, vital signs, water consumption, and urine production. Implications are that total energy balance is altered when an animal is exposed to ectoparasite infestations, thereby resulting in decreased productivity.

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The in vivo metabolism of topically applied 14C-permethrin was determined for adults of pyrethroid-resistant and -susceptible horn flies, Haematobia irritans (L.) at 1, 2, and 6 h after treatment. At 1 and 2 h after treatment, resistant horn flies had significantly higher internal levels of radioactivity (permethrin plus metabolites) compared with adults of the susceptible strain. Analysis of the internal extracts by thin-layer chromatography indicated no differences in the levels of permethrin. However, significantly higher levels of metabolites that co-chromatograph with 3-(2'- or 4'-hydroxyphenoxy)benzyl (1RS) cis/trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane carboxylate at 1 and 2 h after treatment and (1RS) cis/trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane carboxylic acid at 1 h after treatment. These results demonstrate that an enhanced penetration and metabolism are present during the early phases of permethrin intoxication. Enhanced metabolism may contribute to the ability of resistant horn flies to survive in the presence of pyrethroids.

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The possible presence of sand flies (Diptera: Psychodidae) among colonies of Gunnison's prairie dogs, Cynomys gunnisoni Baird, was investigated on or near ranches with histories of vesicular stomatitis (VS) in domestic livestock in the mid-Rio Grande River Valley, NM, and west-slope region of Colorado. Sampling was conducted at six locations, three in each region, using three methods: standard down-draft suction/light traps, up-draft suction/light traps (both supplemented with CO2), and burrow-emergence traps. Two male and four female sand flies, Lutzomyia apache, Young and Perkins were recovered from prairie dog colony and sand-sagebrush association habitats on a cattle ranch in Socorro County, NM. Sand flies were captured only in up-draft suction/light traps. This record is of interest for the following reasons: (1) sand flies have not been reported from the Rio Grande River Valley of New Mexico, (2) sand flies are biological vectors of VS viruses in other areas, (3) the mid-Rio Grande River Valley has been a focus of VS virus activity in domestic livestock during recent outbreaks, and (4) the source of vesicular stomatitis viruses that infect livestock in the western United States is unknown, but may involve introductions of virus from Mexico or an endemic cycle maintained by vector insects.