Blowflies carrying bird flu have been found in southern Japan, raising concerns about a potential new transmission route by which the virus can spread.
In a new study published in the journal Scientific Reports, researchers from Kyushu University collected 648 blowflies, which are known for their attraction to decaying flesh and feces, from a wild crane colony in Izumi City. They discovered that 14 of these blowflies were carrying the virus.
“While 14 blowflies may seem like a low number, this represents a prevalence in blowflies of 2.2 percent, which is a huge percentage compared to other diseases spread by insects,” Ryosuke Fujita, the study’s first author and an associate professor at Kyushu University’s Faculty of Agriculture, said in a statement.
In winter, the peak season for bird flu, thousands of cranes migrate to the Izumi City area, where their dense populations make them particularly vulnerable to infection. During the winter of 2022–2023, 1,600 cranes out of a colony of 10,000 died from bird flu.
Scientists deployed traps at various locations around Izumi City to capture blowflies, and genetic testing confirmed that they carried the same virus strain infecting the crane colony.
“We were notified about the cranes being infected and we had to act quickly,” Fujita said.
“We were particularly interested in one species of blowfly, Calliphora nigribarbis, as, unlike other fly species, they are active in winter, coinciding with the peak season of bird flu. This, along with their attraction to the flesh and feces of animals, makes them a prime suspect for spreading the virus.”
The researchers believe that as blowflies move from place to place, they could contaminate surfaces, food sources and water sources. Healthy birds may then become infected through direct contact with these contaminated sources or by ingesting adult or larval blowflies.
Since 2020, bird flu has spread rapidly across the globe, resulting in the deaths of millions of wild birds and the culling of over half a billion farmed birds worldwide.
