Third wave of African swine fever infection in Armenia: Virus demonstrates the reduction of pathogenicity

Abstract

Aim:First cases of clinically uncommon African swine fever (ASF), caused by virus genotype II are described in this article. These cases occurred in Armenia, Tavush region, Dilijan municipality in 2011. The aim of this study was to identify and describe the new pathogenic forms of ASF in Armenia.Materials and Methods:The isolation and identification of ASF virus (ASFV) were carried out using conventional techniques. Clinical signs of infection were recorded daily. Gross anatomical pathology characteristics were observed during routine postmortem examinations. Blood and serum were obtained by puncture of the jugular vein using a vacutainer system.Results:The presence of ASFV DNA in the spleens was confirmed by polymerase chain reaction. Sequenced sections of p72 showed phylogenetic identity to genotype 2. The pathology exhibits unusual manifestations of the main disease. The unusual form of ASF demonstrates characteristics of a subacute form of the disease, with the possibility of conversion to a chronic form. Decreased lethality, low level of hemorrhages, and absence of severe pancytopenia in smears from spleen, lymph nodes, and blood are common features of the new form of ASF. Unlike severe thrombocytopenia in the typical ASF, the unusual form exhibited moderate or minor decrease of this feature. Despite a moderate decrease in hemadsorption titers, the unusual pattern of the disease was characterized by viremia and the presence of the virus in the visceral organs, including the brain.Conclusion:Our data allow assuming that new nosological form of ASF (genotype II) may present as a transitional form of the disease with the possibility of chronization.

The unique genetic variation within the O174L gene of Polish strains of African swine fever virus facilitates tracking virus origin

“…1). The duplication of the 14-nt long sequence seems to have occurred suddenly, since no intermediate sequences between original and mutated sequences were detected, indicating that this tandem repeat has a higher evolution rate that the whole ASFV genome, a phenomenon that has been observed with other DNA viruses [19]. Genetic data like those presented in this report are essential for the study of ASFV evolution.…”

Replication and virulence in pigs of the first African swine fever virus isolated in China

“…The ASFV usually causes a persistent but asymptomatic infection in its natural hosts, which include warthogs, bush pigs, and soft ticks [3,30,31]. In domestic pigs and Eurasian wild boars, however, disease signs of ASF vary from peracute to chronic disease, and apparently healthy virus carriers are asymptomatic [28,32]. The virulence of different ASFVs in the same host may vary among different strains.…”

Evolution of the ASF Infection Stage in Wild Boar Within the EU (2014–2018)

“…Moderately virulent ASFV are already currently circulating (5)(6)(7)(8). These virulent viruses produce clinical signs and lesions that are compatible with the simultaneous occurrence of acute, subacute, and chronic forms of the disease.…”