Scientists from The Pirbright Institute are a step closer in the race to develop a vital vaccine for African swine fever (ASF).

In their recent trial, published in Vaccines, 100% of pigs immunised with the new vaccine survived a lethal dose of ASF virus.

African swine fever

ASF causes fever, loss of appetite, vomiting and bloody diarrhoea in pigs and wild boar, with case fatality rates reaching 100%.

Major African Swine Fever outbreaks continue to spread across Eastern Europe, Asia and Africa, which in 2019 resulted in the death of nearly seven million pigs.

Without a vaccine or antivirals, the only way to prevent outbreaks is through biosecurity measures and the culling of susceptible animals.

The Pirbright team's vectored vaccine uses a non-harmful virus (the vector) to deliver eight strategically selected genes from the ASF virus (ASFV) genome into pig cells.

Once inside the cell, the genes produce viral proteins which primes the pig immune cells to respond to an ASF infection.

Trials showed that all pigs immunised with the vaccine were protected from severe disease after challenge with an otherwise fatal strain of ASFV, although some clinical signs of disease did develop.

Dr. Chris Netherton, head of Pirbright’s ASF Vaccinology Group, said: “It is very encouraging to see that the genes we have selected are able to protect pigs against ASF.

"Although the pigs showed clinical signs of infection after challenge with the virus, our study has shown for the first time that a vectored vaccine against ASF is a realistic possibility.”

The vaccine will also enable the differentiation of infected animals from those that have received a vaccine. This important feature allows vaccination programmes to be established without sacrificing the ability to trade.

“Our next step will be to uncover the mechanisms behind how the proteins produced by the virus genes stimulate the immune system so we can refine and add to those included in the vaccine to improve effectiveness” added Dr. Netherton.

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."

This research was funded by the Department for Environment, Food and Rural Affairs (Defra) and the Biotechnology and Biological Sciences Research Council (BBSRC), Part of UK Research and Innovation (UKRI).