Molecular Epidemiology of Classical Swine Fever in the Russian Federation

Abstract

The ability to discriminate between various classical swine fever virus (CSFV) strains and isolates is a prerequisite for following the spread of the virus after an outbreak. To determine the relatedness between Russian CSFV isolates from different geographical regions, three fragments of the viral genome (5' NTR, the variable region of the E2 gene and a fragment of the NS5B gene) were sequenced and used for genetic typing. Thirty-one field isolates were obtained from CSF outbreaks which occurred between 1994 and 1999. In addition, three attenuated strains were included in the study, namely the LK and CS vaccine strains, and the moderately virulent 238H isolate. The vaccine strains have been used in Russia for more than 30 years. Our results showed that all field isolates are in subgroup 1.1 together with Alfort 187 and with the highly virulent strain Shimen. In contrast, the CS and LK vaccine strains belong to subgroup 1.2. While there is no evidence for the reversion of the two vaccine strains to wild type, it is feasible that the highly virulent Shimen strain, which has been used as a challenge strain for many years, contributed to field strain generation. The Russian field isolates from the 1990s can be distinguished from the CSF virus isolates which occurred in the EU Member States in the same decade, as here all outbreaks were caused by CSF viruses belonging to subgroup 2.

Genetic characterization of E2 gene of classical swine fever virus by restriction fragment length polymorphism and phylogenetic analysis

“…The disease has been eradicated in several countries or under control in other countries. Sporadical outbreaks were reported in the Americas and Asia as well as some European countries during the past few years [3,4,[10][11][12][13][16][17][18][19]. To control the disease in endemic areas, live attenuated C-strain vaccine has been proven to be efficacious and safe [20,21].…”

Epidemiology, diagnosis and control of classical swine fever: Recent developments and future challenges

“…In Russia, despite vaccination with the LK VNIIVVIM live vaccine, cases in wild boar and outbreaks in domestic pigs have been reported, but only very limited genetic information is available. A recent study emphasizes that in the 1990s predominantly genotype 1 isolates were detected in the Russian Federation, whereas in the more recent outbreaks (2007–2014) predominantly genotypes 2.1 and 2.3 have been reported (Titov, Tsybanov, & Malogolovkin, ; Vlasova et al., ). The recent genotype 2.3 isolates from Russia are phylogenetically closely related to the isolates from Latvia (2012–2015) and to isolates that had caused CSF outbreaks in Central Europe, for example, in France (2003) and in Germany (2006) (Figure b).…”

Control and eradication of Classic Swine Fever in wild boar

“…The phylogenetic analyses performed during the last decade have demonstrated a link between genotype and geographical origin (Bartak and Greiserwilke, 2000;Stadejek et al, 1997;Vilcek, 1997;Vilcek andBelak, 1996, 1997). Since the beginning of the 1990"s, most of the viruses isolated from the outbreaks that occurred in Western Europe, belonged to the group 2, when isolates of the group 1 were still circulating in South America (Frias-Lepoureau and Greiser-Wilke, 2002) or Russia (Vlasova et al, 2003). Viruses belonging to the group 3 seem to be confined within Asia (Parchariyanon et al, 2000).…”

“…The virulence of a strain is difficult to establish as the same isolate can induce different signs depending on the age (younger age animals are more susceptible), the breed , the health status and immune status of the inoculated pigs (Depner et al, 1997;FloegelNiesmann et al, 2003;Moennig et al, 2003).…”