Flies Impacting Livestock, Poultry and Food Safety

Non-Technical Summary:<br/>
House fly is a major vector of numerous food pathogens (e.g., Escherichia coli); and, it has already been suggested that the fly crop is the major reservoir for the pathogen and also that this is where horizontal transmission of antibiotic resistance occurs. The salivary glands of most flies involved in vectoring pathogens are also involved in pathogen transmission and their nutrient and pathogen uptake while feeding. We know very little about those factors involved in the regulation of both crop filling and emptying. At the same time, we know even less about the effect of various pathogens on salivary gland regulation. By better understanding of how these two essential organ systems are regulated, we will obtain a better picture to explore how control strategies can be directed at interfering with the normal regulation of these two organ system. Ultimately, non-traditional control strategies will be developed that rely on interfering with the function of these two systems, which are so essential to the fly. Thus, compromised longevity, pathogen vectoring, and/or reproductive development of the flies can be interfered with resulting in death, abnormal flight ability, and/or reduced fecundity.
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Approach:<br/>
A survey of poultry, dairy and pig farms in Massachusetts will be conducted to compare infection rates of house fly by the salivary gland hypertrophy virus. Once completed, the data should give us some information about the types of foods adult house flies are feeding on and why any differences in infection rates are observed. Adult flies will be sampled during the summer months, quickly frozen, returned to the laboratory where they will be kept frozen until dissected and examined for the salivary gland hypertrophy virus. This study may be also conducted by using PCR on large samples of flies from each type of animal facility. The virus will be maintained at low temperature and removed and used to infect non-infected flies maintained in the laboratory fly room. Both salivary glands and crops of the 3 flies will be used to test various pharmacological agents to study their effect on crop contractions, thus regurgitation and/or passing of the crop contents, which include various pathogens. These effects will be video recorded and contraction rates determined for comparison effects of the agents. Both TEM and SEM studies will be conducted on both the salivary and crop organ systems to help better understand the effect of the pathogenic salivary gland virus on these structures and also to help elucidate the involvement of either nervous or exogenous chemical control.
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Progress:<br/>
2007/10 TO 2012/09<br/>
OUTPUTS: At the moment, the product(s) produced have been shared only with selected individuals of the multistate project, either by emails or by my going to their institution and presenting a seminar (USDA lab. and Dept. of Entomology in Gainesville, Fl and Dept. of Entomology at Riverside, Calif.).
<br/>PARTICIPANTS: Dr. Chris Geden of the USDA lab. in Gainesville, Fl., has been involved with the salivary gland part of this project and also has sent us house fly pupae for our colony. Drs. V. Leitze and D. Boucias, both of the dept. of Entomology at the Univ. of Florida have sent us virus for infecting house flies. They have also read reports and made comments.
<br/>TARGET AUDIENCES: The target audience for the research at the moment includes members of the multistate project interested in novel and new ways of controlling house fly as a major pest of humans/domestic animals.
<br/>PROJECT MODIFICATIONS: One of the most important finds to date is that the crop now serves as a major storage organ for the deadly strain of E. coli and, it is in this organ that horizontal transmission of antimicrobial resistance takes place. To better understand the importance of the crop in maintaining and, its involvement for vectoring this most important food pathogen, a new approach is being taken to look at the crop as an area where the food pathogens form biofilms (i.e., the adult house fly crop as a site for biofilm formation).
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IMPACT: Comparison of the salivary glands of viral infected and non-infected house fly, Musca domestica. 1. A technique was developed to access the production of saliva by the two types of glands and preliminary results show that viral infected salivary glands do not produce any, or little saliva, compared to non-infected glands. This may affect the impact the virus has on biologically controlling house fly adults. Physiological mechanisms controlling crop contractions and movement of fluids into and out of the gland 1. It was demonstrated that serotonin (a neurohormone)stimulates pump 4 of the crop organ system while stimulating pump 4, which is involved in moving fluids out of the crop and forward into either the midgut for digestion or out of the mouth as regurgitation. 2. It was also demonstrated that various channel blockers are able to shut down crop activity and, this in turn could have an impact on normal digestion and/or the process of regurgitation.