Disease dynamics and persistence of Musca domestica salivary gland hypertropy virus infections in laboratory house fly (Musca domestica) populations.

Authors: LIETZE, VERENA-ULRIKE - University Of Florida; Geden, Christopher - Chris; Doyle, Melissa; BOUCIAS, DRION - University Of Florida

Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/25/2011
Publication Date: 1/1/2012
Citation: Lietze, V., Geden, C.J., Doyle, M.A., Boucias, D.G. 2012. Disease dynamics and persistence of Musca domestica salivary gland hypertropy virus infections in laboratory house fly (Musca domestica) populations. Applied and Environmental Microbiology. 78(2):311-317.

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 recent years a promising new biological control agent for adult flies has been discovered, salivary gland hypertrophy virus (SGHV). Female flies infected with the virus do not produce any eggs, and infected males do not compete well with healthy males. One of the goals of the research team studying the virus is to determine whether release of infected flies would result in disease spread and collapse of wild fly populations. In this paper, scientists at USDA-ARS’s Center for Medical, Agricultural and Veterinary Entomology (Gainesville, FL) and the University of Florida (Gainesville) examined virus transmission in fly populations after introducing infected flies of different sexes and at different proportions of infected:uninfected flies. Regardless of the starting ratios, infection rates over time reached an equilibrium level of about 10% infection, and males were more susceptible to infection than females. The results demonstrate that sustained releases of infected flies would be necessary to keep infection levels high in field populations of flies.

Technical Abstract: Past surveys of feral house fly populations have shown that Musca domestica salivary gland hypertrophy virus (MdSGHV) has a world-wide distribution with an average prevalence varying between 0.5% and 10%. How this adult-specific virus persists in nature is unknown. In the present study, experiments were conducted to examine short-term transmission efficiency and long-term persistence of MdSGHV in confined house fly populations. Transmission from virus-infected to healthy flies in small populations of 50 or 100 flies ranged from an average 3% to 24% and did not vary between three tested isolates that originated from different continents. Introduction of an initial proportion of 40% infected flies into fly populations did not result in epizootics. Instead, long-term observations demonstrated that MdSGHV-infection levels declined over time resulting in a 10% infection rate after passing through ten filial generations. In all experiments, transmission efficiency was significantly higher to male flies than to female flies and might be explained by male-specific behaviors that increase contact with viremic flies and/or virus-contaminated surfaces.