The first results of a newly developed vaccine against African swine fever are promising and could pave the way for effective control of this disease. This is the conclusion of ANSES, the French food safety agency, based on a study by the Ploufragan-Plouzané-Niort laboratory.
The Swine Virology and Immunology (VIP) Division of ANSES’ Ploufragan-Plouzané-Niort Laboratory inactivated the Georgia 2007/1 virus strain for the study. This virus is currently circulating in the European Union. During the heat-inactivation process, the research team accidentally discovered an attenuated strain derived from the Georgia strain. This strain caused only mild fever in infected animals, whereas infection with the Georgia strain is normally fatal in 100 percent of cases.
Mild symptoms
The team conducted a series of studies with this attenuated strain and confirmed that most pigs inoculated intramuscularly or oronasally (via aerosols) with this virus showed only mild symptoms and survival was much better than with the original viral strain.
Intramuscular vaccination is the most commonly used method on farms, but the researchers say it could be possible to vaccinate wild boars with bait via oral vaccination. This method was used for classical swine fever in the early 2000s and eradicated the disease in areas of France where it was present. That is also why the French have tested these routes of administration from the start.
Develop immune response
Another promising result of the study is that the deliberately infected pigs with this mild strain develop an immune response, allowing them to resist infection with the ASF virus without showing symptoms as early as two weeks after vaccination.
The scientists at ANSES multiplied the attenuated strain in cell produced in vitro and not in pig cells as usual. This move was a success, which the researchers say opened up the opportunity to produce the vaccine on a large scale. The virus strain produced in this way was also shown to have fewer symptoms than the original attenuated strain, while still being effective.
Not transferable
Studies are ongoing, particularly to ensure that this attenuated strain cannot be passed from one animal to another or become virulent again. The ANSES scientists will also assess the vaccine that animals vaccinated and then exposed to the pathogenic ASF virus retransmit the virus.
No genetic engineering
The vaccine developed by ANSES scientists has the advantage of not being produced by genetic engineering, making it easier to authorize its use in the wild. Indeed, wild boars would likely be the first target for the vaccine in Western Europe. This is the most affected species and the presence of the virus in wild animals poses a risk to pig farms.
Download the research here (English)