By Grace Wairimu

Pig farmers could be facing another challenge in the fight against African Swine Fever, with researchers finding that flies may provide a further route for the virus to reach pigs, explaining how the virus reaches some farms despite strict measures that limit the movement of animals, people, and equipment.

Scientists began investigating stable flies (Stomoxys calcitrans) after African Swine Fever outbreaks occurred on some farms where common sources of infection did not fully explain how the virus spread.

Researchers at Denmark’s National Veterinary Institute found that stable flies could be another possible way African swine fever reaches pigs in a study published in Transboundary and Emerging Diseases.

Earlier research showed that stable flies can pick up African Swine Fever virus after feeding on infected blood and carry it for a period of time afterwards, raising questions about whether they could help move the virus between animals.

The researchers then tested whether pigs could become infected after eating flies that had previously fed on blood infected by the virus. The study involved 12 pigs divided into three groups. Some received infected blood directly, while others ate either crushed infected flies or whole flies hidden in feed.

The pigs that ate the infected flies developed African Swine Fever, with laboratory tests later confirming the virus in their blood. They showed signs of the disease including fever, loss of appetite, and depression.

The findings do not mean that flies are behind every African Swine Fever outbreak. Instead, they show that blood-feeding flies could be one possible way the virus reaches pigs.

For farmers, the research adds fly control as another step that can help reduce African Swine Fever risks.

Farmers can reduce fly risks by removing manure regularly, keeping pig housing clean, managing waste areas, and limiting flies from entering pig shelters through measures such as insect screens.