|Ulricke-Lietze, Verena - UNIVERSITY OF FLORIDA|
|Boucias, Drion - UNIVERSITY OF FLORIDA|
Submitted to: Journal of Medical Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 1, 2007
Publication Date: January 15, 2008
Citation: Geden, C.J., Ulricke-Lietze, V., Boucias, D.G. 2008. Seasonal prevalence and transmission of salivary gland hyperplasia virus of house flies, Musca domestica L. (Diptera:Muscidae). Journal of Medical Entomology. 45(1):42-51. Interpretive Summary: House flies are important pests associated with animals and humans and transmit a wide array of disease organisms. Efforts to manage flies have traditionally relied on chemical insecticides, but flies have become resistant to most insecticides and there is increasing public demand to reduce pesticide use around animals that are used in the production of meat, milk and eggs. Most biological control research on flies has concentrated on targeting fly pupae with parasitic wasps. In contrast, efforts to manage adult flies has been restricted to pathogenic fungi, with mixed results. In this paper, scientists at the University of Florida and USDA-ARS’s Center for Medical, Agricultural and Veterinary Entomology (Gainesville, FL) report on a novel viral disease of adult flies. Fly collections made on four dairy farms during a two-year survey demonstrated the infections to present year-round, and high infection rates were strongly correlated with high fly densities. In the laboratory, healthy flies became infected after they fed on food that was collected from the field and from lab food that was contaminated by infected flies. Various testing approaches confirmed that flies do not acquire the infection before they become adults. Infected flies were calculated to deposit 100 million virus particles per hour when they are feeding.
Technical Abstract: A survey (2005-2006) of house fly (Musca domestica L.) populations on four Florida dairy farms demonstrated the presence of flies with acute symptoms of infection with salivary gland hyperplasia (SGH) virus on all farms. Disease incidence varied among farms (farm averages, 0.5-10.1%) throughout the year, and showed a strong positive correlation with fly density. Infections were most common among flies that were collected in a feed barn on one of the farms, especially among flies feeding on wet brewers grains (maximum 34% SGH). No infections were observed among adult flies reared from larvae collected on the farms, nor among adults reared from larvae that had fed on macerated salivary glands from infected flies. Infected female flies produced either no or small numbers of progeny, none of which displayed SGH when they emerged as adults. Healthy flies became infected after they fed on solid food (a mixture of powdered milk, egg, and sugar) that had been contaminated by infected flies (42%) or after they were held in cages that had previously housed infected flies (38.6%). Healthy flies also became infected after they fed on samples of brewers grains (6.8%) or calf feed (2%) that were collected from areas of high fly visitation on the farms. Infection rates of field-collected flies increased from 6% to 40% when they fed exclusively on air-dried cloth strips soaked in a suspension of powdered egg and whole milk. Rates of virus deposition by infected flies of food were estimated by qPCR at approximately 100 million virus copies per fly per hour. Electron microscopy revealed the presence on enveloped virus particles in the lumen of salivary glands and on the external mouthparts of infected flies.