ARS | Publication request: Musca domestica Salivary Gland Hypertrophy Virus, a Globally Distributed Insect Virus that Infects and Sterilizes Female Houseflies

Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 7, 2009
Publication Date: February 1, 2010
Citation: Prompiboon, P., Lietze, V., Denton, J., Geden, C.J., Steenberg, T., Boucias, D.G. 2010. Musca domestica Salivary Gland Hypertrophy Virus, a Globally Distributed Insect Virus that Infects and Sterilizes Female Houseflies. Applied and Environmental Microbiology. 76(4):994-998.

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 have been restricted to pathogenic fungi, with mixed results. In this paper, scientists at the University of Florida, USDA-ARS’s Center for Medical, Agricultural and Veterinary Entomology (Gainesville, FL), and the University of Aarhus (Denmark) report on a novel viral disease of adult flies. This virus, called SGHV, infects the salivary glands of adult flies and renders them sterile. Virus collections were made from a wide range of locales (multiple locations in the US, Thailand, Denmark, and the Virgin Islands) and compared for infectivity and genetic similarity. The isolates varied in their virulence and were genetically distinct but there was no evident genetic marker that correlated with virulence. The results indicate that further exploration may reveal superior isolates for use in fly management programs.

Technical Abstract: The house fly, Musca domestica, is a cosmopolitan pest of livestock and poultry that is of economic, veterinary, and public health importance. Populations of M. domestica are naturally infected with salivary gland hypertrophy virus (MdSGHV), a non-occluded dsDNA virus that inhibits egg production in infected females and is characterized by salivary gland hypertrophy (SGH) symptoms. MdSGHV has been detected in house fly samples from North America, Europe, Asia, the Caribbean and the Southwestern Pacific. In this study, house fly samples were collected from various locations and dissected to observe SGH symptoms, and the infected gland pairs were collected for MdSGHV isolation and amplification in laboratory-reared house flies. Geographic differences among the isolated MdSGHVs were examined by biological and molecular approaches. The virulence of these geographic MdSGHV isolates was evaluated by per os treatments of newly emerged and 24-h-old house flies. Results showed that infectivity varied among the different isolates but was not correlated to viral copy numbers per infected gland pair equivalent as estimated by quantitative PCR. In all cases 24-h-old flies displayed a resistance to oral infection that was significantly greater than that displayed by newly eclosed adults. Approximately 600-bp nucleotide sequences from each of five open reading frames encoding DNA polymerase and four per os infectivity factor proteins (p74, pif-1, pif-2, and pif-3) were selected for phylogenetic analyses. Nucleotide sequences from 15 different geographic isolates showed polymorphism that correlated with geographic source. The variation observed in biological activity does not correspond to genotypic variation.