Improved vaccines and stronger surveillance are needed to combat African swine fever as it threatens pig populations around the world, say a team of researchers from The Pirbright Institute.
African swine fever (ASF) is one of the most serious diseases affecting pigs. It can kill almost all infected animals and has caused devastating losses for farmers, businesses and national economies across Europe, Asia and Africa.
Although there is no risk to human health, ASF outbreaks have a major impact on food production and livelihoods. As the disease continues to spread, researchers are working to develop vaccines that can help protect pigs and reduce its impact.
Writing a commentary in Emerging Microbes and Infections, the Pirbright scientists highlight both the progress made in African swine fever vaccine development and the challenges faced before vaccines can be used safely and effectively on a wider scale.
Hope from new vaccines
For many years, developing a vaccine against ASF proved extremely difficult because the virus is unusually large and complex. Recently, researchers have made significant progress with a type of vaccine known as a live attenuated vaccine. These vaccines use a weakened version of the virus that can stimulate an immune response without causing severe disease. Several of these vaccines have shown promising results, and three have now been licensed for use in Vietnam. They are considered an important step forward in the global fight against ASF.
Warthog (Phacochoerus africanus) in natural habitat, Kruger National Park, South Africa
The challenge of a changing virus
One of the biggest obstacles facing vaccine developers is the diversity of ASF viruses circulating around the world. Different strains of the virus can vary significantly, meaning a vaccine that works well against one strain may offer little protection against another.
Research shows current vaccines based on the most widespread strain, known as genotype II, provide strong protection against closely related viruses. However, they appear to offer limited protection against some other strains circulating in Africa and parts of Asia.
Scientists are particularly concerned about the emergence of hybrid ASF viruses, which contain genetic material from two different virus strains. These hybrids have already been detected in several Asian countries and are spreading in some regions.
"The effectiveness of a vaccine depends on how closely it matches the strains circulating in the field," said lead author Dr Ana Reis. "Good surveillance is essential to ensure the right vaccines are used in the right places."
Safety remains a priority
While live attenuated vaccines offer the greatest promise for controlling ASF, they also present challenges. Researchers are investigating strategies to reduce the persistence of vaccine viruses in animals and limit their spread to other animals. This would decrease the risk of the emergence of new viral variants.
Although these risks are considered manageable through careful testing and regulation, scientists say further improvements are needed to make vaccines safer and better suited for long-term use.
Looking to the future
The researchers say the next generation of ASF vaccines should aim to provide broader protection against multiple virus strains while maintaining high safety standards.
There is also growing interest in developing vaccines that allow authorities to distinguish between vaccinated animals and infected animals. This would help disease monitoring and support efforts to control outbreaks. Other vaccine approaches, including non-live vaccines, are also being explored. While these may offer safety advantages, they have not yet provided the level of protection needed for widespread use.
A global effort
International organisations, including the World Organisation for Animal Health (WOAH), the Food and Agriculture Organization of the United Nations (FAO) and the African Union, have emphasised the importance of continued investment in vaccine research, disease surveillance and biosecurity measures.
The authors say vaccines will play an increasingly important role in controlling African swine fever, but are not a standalone solution. Effective surveillance, strong biosecurity practices and continued scientific research will all be essential to stay ahead of a virus that continues to evolve.
As ASF spreads into new regions and new virus variants emerge, developing safer and more broadly effective vaccines remains one of the livestock sector's most urgent challenges.