Genetic diversity of PRRSV 1 in Central Eastern Europe in 1994-2014: origin and evolution of the virus in the region

Abstract

More than 20 years after the first outbreaks, the phylogenetic picture of PRRSV is still incomplete and full of gaps, especially in regards of PRRSV 1. Due to the exceptional diversity observed at the eastern borders of Europe and the low number of available sequences from Central Eastern European countries, the authors collected and analyzed both recent as well as already submitted sequences comparing them to a large backbone set of available ORF5 sequences representing the full spectrum of PRRSV 1 Subtype 1 diversity to conduct a systematic phylogenetic analysis and reclassification elucidating the diversity of the virus in these countries. Moreover, further analyses of the EUROSTAT data regarding the live pig movement trends revealed their influence of virus diversity and evolution. The results indicate that besides the effect of local, isolated divergent evolution and the use of modified live vaccines, the most important factor influencing a given country's virus diversity is the transboundary movement of live, infected animals.

Figure 1

Summary results of phylogenetic analysis (green – Western European countries, orange – CEE countries, blue – outside of Europe, yellow – EE countries).

Figure 2

Phylogenetic tree of PRRSV 1 Subtype 1 ORF5 sequences constructed in MrBayes. PRRSV 2 prototype strain VR2332 (AY150564) was used as an outgroup. Three main genetic lineages were distinguished, lineages 1 and 3 containing further clades 1A–1G and 3A–3G, respectively. General geographical distribution was indicated for main clades and lineage 2. Posterior probability values supporting main nodes were shown.

Figure 3

Phylogenetic tree of lineage 1 based on ORF5 sequences constructed in MrBayes. PRRSV 2 prototype strain VR2332 (AY150564) was used as an outgroup. Some minor clusters were collapsed for clarity. Geographical origin and year of isolation were indicated for each sequence. Details of sequences from 1A–1 G clades were shown in the side panel. Posterior probability values supporting main nodes were shown.

Figure 4

Phylogenetic tree of lineage 2 based on ORF5 sequences constructed in MrBayes. PRRSV 2 prototype strain VR2332 (AY150564) was used as an outgroup. Posterior probability values supporting main nodes were shown. Geographical origin and year of isolation were indicated for each sequence.

Figure 5

Phylogenetic tree of lineage 3 ORF5 sequences constructed in MrBayes. PRRSV 2 prototype strain VR2332 (AY150564) was used as an outgroup. Some minor clusters were collapsed for clarity. Posterior probability values supporting main nodes were shown. Geographical origin and year of isolation were indicated for each sequence. Braces indicate clades 3 A–3 G.