August 6, 2024

 

Blowflies linked to bird flu spread in southern Japan, researchers find

Researchers from Kyushu University have identified blowflies as potential carriers of the bird flu virus in southern Japan, revealing a new possible transmission route for the disease, Phys.org reported.

 

Their findings, published in Scientific Reports, suggest that innovative countermeasures are needed to control and prevent bird flu outbreaks in poultry farms.

 

Since 2020, bird flu has rapidly spread worldwide, causing millions of wild birds' deaths and the culling of over half a billion farmed birds globally. In Japan, where a single case of infection on a poultry farm necessitates the culling of the entire stock, the 2022–2023 winter season experienced a record 326 bird flu outbreaks, leading to the sacrifice of 17.7 million birds.

 

Some strains of bird flu have also crossed over to mammals, including cows, goats, dogs, and cats. Since March, an increase in cases among poultry and dairy workers, coupled with a high fatality rate, has raised significant concerns.

 

"Bird flu has been causing substantial damage to wildlife and the poultry industry and poses a significant risk to humans working closely with livestock. It's crucial to understand the virus's transmission routes to control and prevent outbreaks," explained Associate Professor Ryosuke Fujita of Kyushu University's Faculty of Agriculture, the study's first author.

 

The research focused on a wild crane colony in Izumi city, Kagoshima Prefecture, in southern Japan. During the winter, a peak season for bird flu, thousands of cranes migrate to this area, where their dense population makes them vulnerable to infection. In the 2022/23 winter, 1,600 out of 10,000 cranes in the colony died from bird flu.

 

"We were notified about the infected cranes and had to act quickly," said Fujita. Together with his colleagues, Fujita set traps at various locations around Izumi city to collect blowflies. "We focused on the blowfly species Calliphora nigribarbis, which is active in winter and attracted to decaying flesh and faeces, making it a prime suspect for spreading the virus," he added.

 

The team collected 648 blowflies, finding that 14 carried the bird flu virus. Most virus-positive blowflies were collected near the crane colony.

 

"Although 14 blowflies may seem small, this represents a 2.2% prevalence in blowflies, which is a significant percentage compared to other insect-borne diseases," Fujita explained. Genetic testing confirmed that the blowflies carried the same virus strain infecting the crane colony.

 

Unlike birds and mammals, where the virus replicates internally, blowflies ingest the virus from infected birds or waste, with the virus remaining infectious for up to two days. Blowflies can travel at least 2 km daily, making it feasible for them to reach nearby poultry farms or other wild bird populations within a 4-kilometer range.

 

The researchers suggest that blowflies could contaminate surfaces, food, and water sources, with healthy birds becoming infected through direct contact with these sources or by ingesting adult or larval blowflies.

 

In Japan, where closed farming systems are often used to control infections and maximise production, countermeasures aimed at eliminating blowflies can be implemented relatively easily, helping protect farmers from severe financial damage.

 

"By keeping areas clean and using fly control methods, such as fine nets or insecticides, we can reduce the risk of virus spread to indoor poultry farms. However, controlling blowflies in outdoor farms in other countries and wild bird populations may be logistically impossible," Fujita said.

 

Having identified that blowflies carry the virus, Fujita and his colleagues are collaborating with the government to capture blowflies in quarantined sites around infected poultry farms, hoping to find definitive evidence that blowflies are causing these outbreaks.

 

The research team is also developing new tools that use artificial intelligence to assess and predict the potential risks of vector insects. "By combining advanced technologies with on-the-ground research, we can better understand and control the spread of bird flu and other insect-borne diseases, ultimately safeguarding animal and human health," concluded Fujita.

 

-      Phys.org