New genotype of ASF virus identified in China

According to a report published in scientific journalism (Genotype I African swine fever viruses emerged in domestic pigs in China and caused chronic infection - PubMed (nih.gov)) a new genotype of the African swine fever (ASF) virus has been identified in China .

So, in the presented materials of Chinese researchers Encheng Sun et al. it is reported that in China at the moment, along with isolates of the genotype II virus (common in the countries of the African, European and Asian continents, the Malay Archipelago, the countries of Oceania and the Caribbean), the non-hemadsorbing ASF virus of genotype I is also isolated. Two strains (HeN / ZZ-P1 / 21 and SD / DY-I / 21) of this virus were isolated from pig farms in Henan and Shandong, respectively. Animal testing has shown that the SD/DY-I/21 strain exhibits low virulence and efficient transmission in pigs, as well as mild onset of infection and chronic disease. Experiments have shown that SD/DY-I/21 causes necrotic skin lesions and joint swelling in animals.

A similar picture was observed in Portugal and Spain in the 60s of the 20th century, when vaccination with attenuated vaccines led to a 3-6-fold increase in the number of points unfavorable for ASF, the death of 10-50% of the vaccinated livestock, and the manifestation of clinical signs of the disease in pigs in the post-vaccination and remote periods, as well as a change in the serotype of the circulating variant of the virus.

This phenomenon may be due to two possible ways of origin of new variants of the ASF virus:

1. The virus originally introduced into the territory of these countries was heterogeneous in its composition, therefore, immune protection against one virus genotype is not able to prevent the replication of the minor component of this virus population.

2. An insufficiently high level of protection against ASF after the use of live vaccines leads to the circulation of the virus in immune animals and facilitates its escape from immunity effectors by changing its serotype or genotype.

The circulation of the ASFV genotype I creates new challenges for disease control and prevention in China, and poses a risk of spread to new regions and countries, incl. regions of the Far East of the Russian Federation, which requires adjustment of the schemes for diagnosing the infection.

In this regard, in order to control the ASF epizootic situation, it is necessary to use diagnostic tools that allow the detection of the virus and / or its genome belonging to both the II and I genotypes and having passed the appropriate verification in comparative tests.

Rosselkhoznadzor strongly recommends that all economic entities working in the field of pig breeding conduct operational representative laboratory monitoring of their products.

Press service of the FGBI "ARRIAH"