The potential of house flies to act as a vector of avian influenza subtype H5N1 under experimental conditions

WANARATANA, S.; PANYIM, S.; PAKPINYO, S.

The objective of the present study was to determine the potential for house flies (Musca domestica L.) (Diptera: Muscidae) to harbour the avian influenza (AI) H5N1 virus. Laboratory‐reared flies were experimentally fed with a mixture containing the AI virus. Exposed flies were washed with brain–heart infusion broth and followed by 70% alcohol before preparation of whole fly homogenate. The homogenate was inoculated into six 10‐day‐old embryonated chicken eggs (ECEs). Allantoic fluids were collected to determine the virus using the haemagglutination (HA) test, reverse transcription‐polymerase chain reaction (RT‐PCR) or quantitative real‐time RT‐PCR (RRT‐PCR). In the first experiment, ECEs that were inoculated with the 50 AI virus exposed fly homogenates died within 48 h and HA and RT‐PCR were positive for AI virus. In the second experiment, ECEs that were inoculated with only one fly died with positive HA test and RT‐PCR. In the last experiment, a group of exposed flies was collected at 0, 6, 12, 24, 36, 48, 72 and 96 h post‐exposure. Fly homogenates of each time point were tested by virus titration in ECEs and RRT‐PCR. Virus titres declined in relation to exposure time. Furthermore, RRT‐PCR results were positive at any time point. The present study shows that the flies may harbour the AI virus and could act as a mechanical vector of the AI virus.