PRESS RELEASE (2024/08/01)

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Tiny flyers with large impact: Blowflies carry bird flu virus
A new study from a wild bird colony in southern Japan reveals that blowflies are a potential means of bird flu
transmission.

Fukuoka, Japan – Researchers from Kyushu University have discovered that blowflies, a familyof flies strongly attracted to decaying flesh and feces, are carrying the bird flu virus in southern
Japan. Their findings, published in Scientific Reports, introduce a potential new route oftransmission for bird flu and highlight the need to develop new countermeasures to preventand control the disease in poultry farms.
Since 2020, bird flu has been spreading rapidly around the globe, leading to the death ofmillions of wild birds and the culling of more than half a billion farmed birds worldwide. InJapan, where a single case of infection on a poultry farm mandates the culling of the entire
stock, the 2022-2023 winter season saw a record-high of 326 outbreaks of bird flu, resulting
in the sacrifice of 17.7 million birds. Some strains of bird flu have also jumped to mammals,
including cows, goats, dogs, cats, and since March, an uptick of cases in poultry and dairy
workers, with a high fatality rate, has raised significant concern.
"Bird flu has been causing substantial damage to wildlife and the poultry industry, and also
holds great risk for humans who work closely with livestock. It’s therefore vital to understandhow the virus spreads and its potential routes of transmission to control and prevent
outbreaks," explains first author Associate Professor Ryosuke Fujita of Kyushu University’s
Faculty of Agriculture.
In this research, the scientists studied a wild crane colony in Izumi city, Kagoshima Prefecture,
in southern Japan. In winter, the prime season for bird flu, thousands of cranes migrate to thisarea, with their dense numbers making them vulnerable to infection. During winter 2022-2023,
1600 cranes out of colony of 10000 cranes died from bird flu.
"We were notified about the cranes being infected and we had to act quickly,” says Fujita.
Along with his colleagues, he set traps at different locations around Izumi city to collectblowflies. "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," adds Fujita.
The researchers collected 648 blowflies and discovered that 14 blowflies were carrying the birdflu virus. The majority of virus-positive blowflies were collected from the sample site closest tothe crane colony. "While 14 blowflies may seem like a low number, this represents aprevalence in blowflies of 2.2%, which is a huge percentage compared to other diseases spreadby insects,” explains Fujita. The research team also used genetic testing to confirm that theblowflies were carrying the same virus strain that has been infecting the crane colony.

Unlike birds and mammals which the virus infects and replicates inside, blowflies instead ingest
the virus from infected dead birds or their waste, with the virus maintaining infectivity for up
to two days. Blowflies are capable of flying at least 2 kms per day, so the researchers estimatethat is it feasible for them to reach nearby poultry farms or other wild bird populations within
a 4 km range. The researchers believe that as the blowfly moves from place to place, it could
contaminate surfaces, food sources and water sources, with healthy birds becoming infected
through direct contact with these contaminated sources, or by ingesting adult or larval
blowflies.
In Japan, where farmers often use closed farming systems instead of open spaces to control
infections and maximize production, countermeasures aimed at eliminating blowflies could be
implemented fairly easily, helping to protect farmers from severe financial damage.
"By keeping areas clean and using fly control methods, such as fine nets or insecticides, wecan reduce the risk of virus spread to indoor poultry farms. However, in outdoor farms in othercountries, and in wild bird populations, controlling blowflies may be logistically impossible,”says Fujita.
Having identified that blowflies carry the virus, Fujita and his colleagues are now collaboratingwith the government to capture blowflies in quarantined sites around infected poultry farms,
hoping to find definitive evidence that blowflies are causing these outbreaks. Fujita and hiscolleagues are also developing new tools that use artificial intelligence to assess and predictthe potential risks of vector insects. "By using advanced technologies alongside on-the-groundresearch, we can better understand and control the spread of bird flu and other insect-borne
diseases, ultimately safeguarding both animal and human health,” concludes Fujita.
###For more information about this research, see Fujita, R., Tachi, T., Hino, M. et al. Blowflies
are potential vector for avian influenza virus at enzootic area in Japan. Sci Rep 14, 10285(2024). https://doi.org/10.1038/s41598-024-61026-1
About Kyushu University
Founded in 1911, Kyushu University is one of Japan's leading research-oriented institutes ofhigher education, consistently ranking as one of the top ten Japanese universities in theTimes Higher Education World University Rankings and the QS World Rankings. Theuniversity is one of the seven national universities in Japan, located in Fukuoka, on the islandof Kyushu—the most southwestern of Japan’s four main islands with a population and landsize slightly larger than Belgium. Kyushu U’s multiple campuses—home to around 19,000
students and 8000 faculty and staff—are located around Fukuoka City, a coastal metropolisthat is frequently ranked among the world's most livable cities and historically known asJapan's gateway to Asia. Through its VISION 2030, Kyushu U will “drive social change withintegrative knowledge.” By fusing the spectrum of knowledge, from the humanities and arts
to engineering and medical sciences, Kyushu U will strengthen its research in the key areas ofdecarbonization, medicine and health, and environment and food, to tackle society’s mostpressing issues.

Fig. 1. Transmission of bird flu from infected wild birds to other wild birds or poultry via blowflies.

Fig. 2. Wild crane colony in Izumi City, Kagoshima, Japan. (Ryosuke Fujita, Kyushu University)

Fig. 3. The blowfly, a potential means of bird flu transmission. (Ryosuke Fujita, Kyushu University)[Contact]
Ryosuke Fujita, Associate Professor
Faculty of Agriculture, Graduate School of Bioresource and Bioenvironmental Sciences
Tel: +81-92-802- 4970
E-mail: r-fujita@agr.kyushu-u.ac.jp