In vitro Acquisition and Retention of Low-Pathogenic Avian Influenza H9N2 by Musca domestica (Diptera: Muscidae)

Avian influenza virus (AIV) H9N2 emerged in the 1990s as an economically important disease in poultry and occasionally infects humans and other mammals. The aim of this study was to evaluate the acquisition and retention of H9N2 AIV on and within the house fly, Musca domestica (Linnaeus 1758), under laboratory conditions. In first experiment, 100 adult house flies were divided into control and treatment groups equally. Treatment group was fed with a meal containing H9N2 virus, while control group was supplied with an identical meal without virus. Fifteen minutes after exposure in each group, flies were washed twice to remove surface particles, disinfected and then homogenized for testing. The two external body surface washes and the homogenate samples were tested for H9N2 to distinguish exterior from interior viral load. Second experiment was performed likewise but five flies from each group were taken at 0, 6, 24, 48, 72, 96, and 120 h post-exposure. All samples were subjected to real-time reverse-transcription polymerase chain reaction (RRT-PCR) for detecting H9-Specific viral RNA. Results of the first experiment showed that viral RNA was detectable in both of external surface and homogenates samples. Second experiment revealed that persistence of H9N2 AIVs on external body surface and within the body of M. domestica were 24 and 96 h, respectively. Moreover, viral RNAs concentration declined during the time after exposure to AIV H9N2 either outside or within house flies. Overall, house fly was able to acquire and preserve H9N2 AIV experimentally, which may contribute the spread of virus among poultry farms.