A new study shows wild boar may be immunized against the most significant worldwide threat to the swine industry by a vaccine administered via their food. Published in Frontiers in Veterinary Science, it is the first report of a promising inoculation against African swine fever in wild boar. The study also provides evidence that this immunity can be passed on via contact with immunized individuals, but further studies are needed to examine exactly how this occurs, as well as the safety of repeated administration.

“African swine fever is of enormous concern to the pig industry,” says Jose Angel Barasona, a researcher at the VISAVET Health Surveillance Centre and co-author of this research. “Our study demonstrates the effectiveness of the first oral vaccine against this disease on Eurasian wild boar. Overall, we demonstrate that oral immunization of wild boar conferred 92% protection against a highly pathogenic strain of African swine fever, which is currently circulating in Asia and Europe.”

ASF affects more than 55 countries on three continents, including China, which contains nearly half of the world’s pig population. It is highly contagious and can be spread via contaminated feed and pork products, as well as shoes, clothes, vehicles, knives and equipment. Transmission can also occur by the movement of infected livestock and across wild boar populations. It is this latter form of infection that Barasona and his colleagues hope to prevent.

“Wild boar is the most severely affected by this virus in Europe and to date, none of the control measures have been effective,” Barasona says. “The importance of vaccinating wild boar was demonstrated during the 2000s when classical swine fever affected different European countries, and an oral vaccine was used to reduce the incidence of infection in the wild populations in Germany.”

The complex nature of the ASF virus, gaps in knowledge concerning infection and immunity, as well as technical difficulties, have hindered vaccine development. But in 2017, a wild boar in Latvia provided a breakthrough.

“Serum from a wild boar hunted in Rietumpieriga, Latvia, was confirmed as African swine fever virus positive at the EU reference laboratory in Madrid, Spain,” Barasona says. “This was a weakly virulent strain of the disease, which enabled us to produce a live vaccine. When we inoculated wild boar in our laboratories with this live strain, they showed no symptoms of this disease but produced antibodies against the virus, ultimately giving them protection against the more dangerous form.”

When tested, as well as proving its effectiveness against one of the most dangerous strains of ASF, it revealed an additional capability to immunize other wild boar through contact with orally vaccinated animals.

“The ‘shedding’ of this vaccine might help amplify vaccination coverage, reducing the need for expensive production and large-scale administration of vaccine in the field,” says Barasona.

This vaccine, which would be administered in bait to the wild animals, represents considerable progress in the control of ASF in the wild and, subsequently, at the domestic/wildlife interface. However, Barasona cautions more research is needed before it can be used widely.

“If the safety of the vaccine can be established, then it may help mitigate the uncontrolled spread of African swine fever across Europe and Asia, like the success so far in halting the spread of classical swine fever,” Barasona says. “Future studies should examine the vaccine’s safety following repeated administration, the process of ‘shedding’ and its genetic stability during passage from one animal to another.”

Source: Frontiers in Veterinary Science, which is solely responsible for the information provided, and wholly owns the information. Informa Business Media and all its subsidiaries are not responsible for any of the content contained in this information asset.