Flies Impacting Livestock, Poultry and Food Safety

NON-TECHNICAL SUMMARY: Stable flies are economic pests of grazing beef and dairy cattle. Their presence is repsonsible for lowered weight gains, reduced milk production and lowered weaning weights. This project examines development, overwintering and dispersal of stable flies with the results incorporated into stable fly management strategies. This study may help explain why some cattle producers are experiencing stable fly problems early in the season.

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APPROACH: Starting in the summer of 2007 we will begin a nationwide survey of insecticide resistance in house flies, using both bioassays and genotyping of the alleles involved in insecticide resistance. We anticipate evaluating one class of insecticides each year starting with pyrethroids (permethrin and cyfluthrin). The general plan is for cooperators across the USA to collect house flies (by sweep net), and obtain detailed histories of insecticide use, from one to five facilities (dairy, poultry or hog) across their state. Files would be brought back to the laboratory and eggs would be collected. Emerging flies would be used for bioassays by the lab making the collections. To standardize and facilitate the bioassays, each lab will be provided (by J. Scott) with the insecticide, and with a detailed protocol for how to carry out the tests. Each lab making collections will be required to buy a limited number of glass jars (as specified in the protocol), acetone and pipettes. Pupae (~500) from field collected flies would be sent to Cornell Univ. for genotyping. J. Scott and D. Rutz will seek additional funds to cover the sequencing costs (estimated at $800 per site). Availability of these funds will determine the number of collections for which we are able to genotype (50-100) individuals.
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PROGRESS: 2007/01 TO 2007/12
OUTPUTS: To assess the impact of a 2007 WNV epizootic in an American white pelican colony Medicine Lake NWR in northeast Montana, counts of dead pre-fledged pelicans were being made twice weekly from July through mid-August. During a mid-July assessment, flies were observed feeding on moribund pre-fledges and were collected from the birds and identified as stable flies. A total of 1,291 stable flies (83% male, 17% female) were collected. Eight percent of the flies were blood fed (i.e., had visible blood in their abdomen). Flies without visible blood were pooled (60 pools each containing up to 20 flies) and assayed for WNV. Eighteen of 60 pools were positive for WNV. These findings were disseminated during a symposium (Vector-borne pathogens of Livestock and Wildlife) sponsored by the Society for Vector Ecology and at the annual conference of the Northwest Mosquito and Vector Control Association. PARTICIPANTS: Participants from Montana State University include Kristina Hale, Marni Rolston and Anya jackson. Partner organizations include Arbovirus Diseases Branch, Centers for Disease Control and Prevention, Fort Collins, CO. TARGET AUDIENCES: This study describes the increased risk of WNV transmission to personnel working with colonial nesting birds (i.e., wildlife biologists, refuge personnel) and the potential risk to the general public. PROJECT MODIFICATIONS: No major changes are considered at this time.
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IMPACT: 2007/01 TO 2007/12
This represents the first report of stable flies feeding on pelicans and first detection of a flavivirus in stable flies. Collaborative studies between USDA-ARS, CDC/CCID/NCZVED and MSU to determine vector potential of stable fly are underway.