Scientists from The Pirbright Institute are a step closer to developing a vital vaccine for African swine fever (ASF), a pig disease that the World Organisation for Animal Health (OIE) has warned could kill a quarter of the world’s pigs, partly due to the absence of a commercially available vaccine. Their study, published in Vaccines, showed that 100 percent of pigs immunised with the new vaccine were protected from a lethal dose of ASF virus (ASFV).

The team created what is known as a vectored vaccine by inserting eight strategically selected ASFV genes into a non-harmful virus, known as a vector. Vectors are used to deliver the genes to pig cells where they produce viral proteins that prime the pig immune system to rapidly respond to an ASF infection. The combination of eight virus genes protected pigs from severe disease after challenge with an otherwise fatal strain of ASFV, although clinical signs of disease did develop.

This is the first time that a vectored vaccine has shown a protective effect against ASF. Further development is needed, but if successful, this vaccine would enable the differentiation of infected animals from those that have received a vaccine (DIVA), which would allow vaccination programmes to be established without sacrificing the ability to trade.

ASF continues to spread across Eastern Europe and Asia, resulting in the death of over seven million pigs worldwide in 2019 and disrupting entire trade systems that are intertwined with the pork industry. Without a commercial vaccine, stringent biosecurity measures and the culling of susceptible animals are the only methods available to bring ASF under control.

Dr Chris Netherton, Head of Pirbright’s ASF Vaccinology Group, commented: “Demonstrating that our vaccine has the potential to fully protect pigs against ASF is a huge step in our vaccine development programme. We have already begun work to refine the genes included in the vaccine to improve its effectiveness and provide more protection.”

Christine Middlemiss, the UK’s Chief Veterinary Officer, said: “This is a very encouraging breakthrough and it means we are one step closer to safeguarding the health of our pigs and the wider industry’s role in global food supply from African swine fever.

“While there has never been an outbreak of African swine fever in the UK, we are not complacent and already have robust measures in place to protect against animal disease outbreaks.

“We will also continue to work closely with the UK pig sector to raise awareness of the risks and advise on maintaining high biosecurity standards.”