Researchers at USDA’s Agricultural Research Service are experimenting with a virus that can prevent house flies from reproducing, thereby reducing the amount of foodborne bacteria spread by these insects. Scientists have discovered that when house flies are infected with the salivary gland hypertrophy virus, females stop producing eggs and males no longer mate, reported ARS’ Agricultural Research magazine.

Common House Fly (musca domestica), c/o Agricultural Research Service
“It’s a way of managing the fly population at the adult level by limiting its ability to reproduce,” said Entomologist Chris Geden of the Mosquito and Fly Unit at ARS’ Center for Medical, Agricultural and Veterinary Entomology (CMAVE). And when fewer flies are able to reproduce, fewer flies are available to carry harmful pathogens such as Salmonella or E. coli, which are harbored in animal feces, to human food sources. The question researchers are focusing on now is how to ensure a higher infection rate among flies exposed to the virus. Normally, the infection rate is low, at about 0.5 to 1 percent. Geden’s team at CMAVE partnered with researchers at the University of Florida and Aarhus University in Denmark to study two populations of house flies – one in Florida and one in Denmark. Both teams found that exposure to a mixture of infected flies and water produced the highest infection rate. When exposed to the virus this way, 56 percent of the flies in the Denmark study and 50 percent of the flies in the Florida study became infected. That’s compared to an infection rate of 37 percent detected at a SGHV “hot spot” at a dairy farm in Gilchrist, Florida. Geden explained how SGHV would be used during fly season to reduce the adult house fly population: “This is not an insecticide. It’s not something you would put out when people are complaining about flies at picnics and expect to get a fast reduction,” Geden told Agricultural Research. “This would be part of an integrated management program in which you would go out early in the year when natural fly populations are just beginning to increase, hit them with the virus to knock down their reproductive ability, and come back 2 to 3 weeks later and do it again.” This intervention is one of several being explored by scientists at CMAVE in Gainesville. In November of last year, Food Safety News reported on another technique being explored by the team – that one involving the use of a chemical that inhibits fly larvae from growing to adulthood.