Dispersal of a blow fly, Calliphora nigribarbis, in relation to the dissemination of highly pathogenic avian influenza virus.

A mark-release-recapture study of the dispersal ability of blow flies, Calliphora nigribarbis, was conducted in Ikumo-Naka, Ato Town, Yamaguchi Prefecture, Japan in December 2004. A location where a fatal avian influenza outbreak had occurred 1 year previously was selected for the present study. A total of 3,884 C. nigribarbis were collected, 1,915 of which were marked and released from 4 different collection sites during 2 successive days. The recapture rate of the released C. nigribarbis ranged from 0.014 to 0.029 among the collection sites, and the overall recapture rate was calculated as 0.022. Based on the distance between the released site and the recaptured site, the dispersal rate of C. nigribarbis was estimated as 256 m/h on the 1st day and 179 m/h on the 2nd day of the experiment, and the maximum dispersal rate observed in this study was estimated as 500 m/h. Taking into account the active period of C. nigribarbis on a fine day (7 h/day), the distance traveled by C. nigribarbis within a day was estimated as 1,789 and 1,250 m/day on average for the 1st and 2nd days, respectively, and the maximum distance was 3,500 m/day. These results suggest that C. nigribarbis could play a role in the mechanical dissemination of avian influenza virus and spread of the outbreak in Japan.