ASFV vaccine candidate tested in wild boar

An article published in Frontiers in Veterinary Science describes the experimental vaccination of wild boar against African swine fever virus (ASFV). Oral immunization of wild boar with a non-haemadsorbing, attenuated ASFV of genotype II conferred 92% protection against challenge with a virulent ASF virus isolate (Arm07).

“African swine fever is of enormous concern to the pig industry,” said Dr. Jose Angel Barasona, a researcher at the VISAVET Health Surveillance Centre in Madrid 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.”

Vaccine development has been hindered by ASFV genetic complexity, gaps in knowledge concerning ASFV infection and immunity, lack of development of neutralizing antibodies, and technical difficulties such as the lack of stable cell lines.

In a previous study, experimental infection of domestic pigs with a weakly virulent, non-haemadsorbing ASFV strain, isolated in 2017 from a hunted wild boar in Latvia (Lv17/WB/Rie1) provided complete protection against a virulent haemadsorbing ASFV genotype II, suggesting the potential use of Lv17/WB/Rie1 as a live attenuated vaccine.

“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 reports. “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 a virulent strain of ASFV, the vaccine candidate 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,” explains Barasona.

The vaccine would be administered in bait to the wild animals. However, Barasona cautions more research is needed before it can be used.

“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. 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.”

Article: Barasona, J.A., Gallardo, C., Cadenas-Fernández, E., Jurado, C., Rivera, B., Rodríguez-Bertos, A., Arias, M., Sánchez-Vizcaíno, J.M. (2019) First Oral Vaccination of Eurasian Wild Boar Against African Swine Fever Virus Genotype II. Frontiers in Veterinary Science, 6:137, doi: 10.3389/fvets.2019.00137