Multiple vaccine candidates in the works for African swine fever

For years, researchers have been working to develop a safe, effective, and commercially available vaccine for African swine fever as it continues to spread in Russia and most of Europe and Asia, including China. Millions of pigs have been depopulated around the globe because of this highly contagious, deadly disease that affects both domestic and feral pigs and has no cure. But there is some hope.

Recently, the agriculture secretary of the Philippines, William Dar, said the first trials of an ASF vaccine candidate were being conducted on 10 farms. Vietnam’s deputy minister of agriculture and rural development, Phung Duc Tien, said Vietnam plans to produce and commercialize an ASF vaccine in the third quarter of this year.

In addition, an ASF vaccine candidate developed by researchers at the Harbin Veterinary Research Institute at the Chinese Academy of Agricultural Sciences have reportedly seen promising results in clinical trials conducted on 3,000 pigs.

Indoor swine facility
The successful development of safe and effective modified live vaccines represents a new frontier in protecting swine from African swine fever.

More than 35 countries are now impacted by the disease, including the Dominican Republic and Haiti, which reported their first confirmed ASF cases in 2021. In China, outbreaks since August 2018 have killed millions of pigs, with estimates from the American Society for Microbiology suggesting the losses were as high as 225 million pigs.

The successful development of safe and effective live attenuated vaccines represents a new frontier in protecting swine from ASF.

“Developing a live attenuated virus vaccine is a complex process depending on a variety of factors, and it could take several years to develop and license a vaccine for ASF,” said Christina Lood, senior director of sustainability and innovation communications at Zoetis.

Scientists at the University of Connecticut and the U.S. Department of Agriculture have developed a new ASF live attenuated vaccine. This candidate was licensed for commercial development by Zoetis in September 2019.

Dr. Guillermo Risatti, professor of pathobiology at UConn’s College of Agriculture, Health, and Natural Resources and director of the Connecticut Veterinary Medical Diagnostic Laboratory, collaborated with USDA Agricultural Research Service scientists Dr. Manuel Borca and Douglas Gladue, PhD, to develop the vaccine candidate, called ASFV-G-ΔMGF. The CVMDL is one of UConn Extension’s active service centers that works with federal and state veterinary agencies to enhance disease surveillance and response.

The ARS previously announced in May 2021 that Drs. Borca and Gladue had developed the ASFV-G-∆I177L vaccine candidate. The candidate does not rely on live pigs and their cells for vaccine production, which allows for the production of an ASF vaccine on a commercial scale.

Building on that work, researchers from Zoetis and the Friedrich Loeffler Institute in Germany conducted trials of ASFV-G-ΔMGF, also a live attenuated vaccine, in edible bait for wild boars and intramuscular injection for domestic pigs. According to UConn, both routes demonstrated efficacy against ASF.

Lood of Zoetis said the studies demonstrated that this is a promising candidate. She said: “However, more research is needed to better understand safety aspects. Finding the right balance between efficacy and safety is the essential and most challenging aspect of live attenuated vaccines.”