Phylogenetic analysis of bluetongue virus serotype 4 field isolates from Argentina.

Abstract

Bluetongue (BT) is an insect-transmitted viral disease of ruminant species, which represents a major barrier to the international trade of animals and their products. Bluetongue virus (BTV) has a genome composed of ten linear segments of double-stranded RNA (dsRNA), which code for at least ten different viral proteins. In South America, serological evidence for the presence of BTV has been found in Peru, Argentina, Brazil, Ecuador and Chile. Brazil and Argentina are the only South American countries where BTV has been isolated. In Brazil, only one BTV isolate, serotype 12, has been reported, whereas in Argentina five BTV serotype 4 isolates have been obtained from cattle without clinical signs. Three of these five isolates were isolated during 1999-2001, whereas two of them were obtained as part of the present work. This study describes sequence comparisons and phylogenetic analyses of segments 2, 3, 6, 7 and 10 of the first Argentinean field isolates of BTV. The analysis of segments 2 and 6 resulted in a single cluster of Argentinean sequences into the serotype 4 clade. In addition, the Argentinean sequences grouped within the nucleotype A clade, along with reference strains. The analysis of segments 3, 7 and 10 showed that the Argentinean isolates grouped into the western topotype, indicating that the circulating virus had an African/European origin. Phylogenetic analysis revealed that the Argentinean sequences present a South American genetic identity, suggesting an independent lineage evolution.