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Flies Impacting Livestock, Poultry and Food Safety


Muscoid flies are among the most important pests in livestock and poultry production systems. Two species in particular, house fly (Musca domestica) and stable fly (Stomoxys calcitrans), are responsible for damage and control costs in excess of a billion dollars per year in the United States. Synanthropic flies are vectors of food associated pathogens such as Escherichia coli and Campylobacter coli. While filth flies are vectors of enteric disease organisms to humans, the extent to which these flies contribute to the maintenance and spread of pathogens within and between livestock operations and the community is unknown. Successful completion of this project will provide a better understanding of the interactions between livestock production systems and the life cycles of pestiferous flies. Exploitation of these interactions will provide economically feasible and environmentally friendly technology for reducing the impact of flies on livestock production and human health. The project will develop new control technologies for muscoid flies. These technologies will be disseminated to producers to reduce the abundance of muscoid flies thereby increasing the health and quality of livestock and reducing their economic impact. Objectives: 1)Characterize dispersal and population biology of stable flies and house flies, and develop monitoring methods for use in indoor and outdoor environments. 2)Establish extent of fly-borne dispersal of human and animal pathogens. 3)Improve management tactics for stable flies and house flies. Outputs: This project will produce standard protocols for use in studying stable fly and house fly biology, pathogen interactions and control. Collaborations facilitate studies involving migration, population genetics and insecticide resistance and foster the interdisciplinary research. Recommendations for reducing stable and house fly populations, controlling the spread of pathogens to humans and livestock and maintaining the effectiveness of the available insecticides will be developed and disseminated through extension and outreach programs. Research publications on stable fly and house fly biology, relationships to disease transmission and control strategies will be produced. Expected Outcomes or Project Impacts: This project will develop biological, chemical and cultural control strategies for stable and house flies. Strategies will reduce the impact of flies on livestock, producers and the neighboring residential areas. Models of fly population dynamics will permit producers to economically implement biological and cultural controls before populations reach levels necessitating chemical controls. Characterizing the epidemiology of pathogens will permit producers to develop fly control strategies for reducing food borne pathogens. Models of pathogen dissemination will provide planners with quantitative tools to assist in zoning decisions. The nationwide survey of insecticide resistance will provide critical information on the extent of our fly resistance problem nationwide and will also provide a solid scientific base on which to build cost effective and environmentally sound insecticide resistance management programs.

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NON-TECHNICAL SUMMARY: Two muscoid flies, the house fly (Musca domestica) and stable fly (Stomoxys calcitrans), are responsible for damage and control costs to the livestock and poultry industry in excess of a billion dollars per year in the US. The direct damage these flies inflict upon livestock, their presence as a byproduct of confined livestock and poultry operations has been repeatedly cited as a common nuisance, especially when the flies enter the vicinity of human habitations and urban environments. In spite of their ubiquitous presence, importance as pests, and association with diseases of humans and livestock, our knowledge of the biology of these species is seriously wanting and available control technologies remain inadequate. House flies are considered to be the #1 nuisance pest associated with dairy and other confined animal operations. These flies are capable of carrying more than 65 disease organisms that affect humans and animals such as Escherichia coli strain O157:H7. In poultry production, house flies can transmit Salmonella among flocks; and the spotting of eggs with fly specks, reduces the eggs' market value. Stable flies recently surpassed horn flies as the most important arthropod pest of cattle production. With their painful bites, they can reduce weight gains of cattle on finishing rations up to 20%. A USDA study conducted in TX estimated that stable flies caused $432 million dollars in losses to confined livestock, with pastured livestock not withstanding. In this project we look at the dispersal and population biology of stable flies and house flies, evaluating the movement and migration of these insects in the US. We will evaluate the role of these flies in the dissemination of common bacterial pathogens of livestock, poultry and humans. We will determine the risk associated with fly transport of pathogens from the farm to the neighboring community. Lastly we will develop novel pest management strategies for implementation in integrated pest management programs to reduce pest populations and reduce risk of contracting enteric diseases disseminated by flies.

APPROACH: Objective 1. Characterize dispersal and population biology of stable flies and house flies, and develop monitoring methods for use in indoor and outdoor environments. Standardized monitoring tools will be tested within animal housing facilities and outside animal housing facilities, as efficacy may vary between these environments. Objective 2. Establish extent of fly-borne dispersal of human and animal pathogens. Microbial isolation and detection methods will follow those used by Szalanski et al. 2004. Target organisms include Campylobacter, E. coli and Salmonella species. Samples from flies and livestock will be processed using enrichment broth and conditions to maximize growth. Cultures will be will be tentatively identified and stored at frozen for subsequent PCR testing. Positive cultures will be confirmed using PCR analysis (Szalanski et al. 2004). Conduct laboratory studies to isolate and incriminate flies in the dispersal of disease agents. Adult flies will be collected from beef farms and dairies. Collection devices will be placed near barns on study farms and on properties adjacent to farms (distances will be calculated from GPS coordinates for trap location). Individual flies will be tested using the methods developed by Owens and Szalanski (2005). Viability and reproduction of pathogens in flies will be examined by culturing fly isolates of specific bacteria and conducting laboratory studies on persistence or amplification. Objective 3. Develop house fly control and resistance management tactics. Novel insecticides will be used separately and in combination in broiler-breeder, turkey and dairy farms during the fly season to determine their efficacy in adult fly management. Collected flies will be tested for resistance to these insecticides at the beginning and at the end of the fly season. Rotation with other insecticides will be implemented in an attempt to minimize the development of resistance. New novel insecticides will be include in our studies. Conduct nationwide survey for insecticide resistance. 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. To standardize and facilitate the bioassays, each lab will be provided with the insecticide, and with a detailed protocol for how to carry out the tests. Field collected flies would be sent to Cornell Univ. for genotyping. Information dissemination. Information will also be disseminated to each states beef and dairy associations such as the Cattlemens Association, to beef cattle trade publications, extension assignments, scientific meetings and peer reviewed publications.

Watson, D. Wes
North Carolina State University
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