RESUMO
Israel is endemic to bluetongue virus (BTV). The introduction of novel-for-the-region arboviruses have been recorded annually in recent years. In 2019, previously non-reported in-the-country BTV-1 and BTV-9 were identified. BTV-1 caused a single-season outbreak, probably linked to mild infection in ruminants. BTV-9 was retrospectively detected in the field samples collected from August 2018 until 2020. It was the dominant serotype in 2019, out of the six serotypes recorded during that calendar year. Clinical manifestation of the disease in cases diagnosed with BTV-9 were compared to those in cases determined to have BTV-1. BLAST and phylogenetic analyses of BTV-1 showed that the nucleotide (nt) sequence coding the viral outer protein 1 (VP2) determining the serotype is closely related to BTV-1 isolated in Sudan in 1987, and the coding sequence of the outer protein 2 (VP5) is related to South African BTV-1 from 2017. A probable common ancestor with Libyan BTV-9 strains isolated in 2008 was seen in an analysis of Israeli BTV-9 nt sequences. Notably, the outbreak-caused BTV-9 strains collected in 2019 exhibited a distinct level of genetic reassortment with local Israeli strains compared to BTV-9 strains registered in 2018 and 2020.
RESUMO
The Shuni virus (SHUV) causes an endemic viral infection in Israel and South Africa. It belongs to the Simbu serogroup within the order Bunyavirales, family Peribunyaviridae, genus Orthobunyavirus. Recently, it has been identified in aborted cases of domestic ruminants, young cattle and horses manifesting neural signs and acute death, symptomatic cows, and in carcasses of wild animals. Moreover, SHUV was isolated and identified in humans. In this study, we describe clinical cases of SHUV infection in Israeli domestic ruminants in 2020-2021, which represented clinical manifestations of simbuviral infection including abortions, a neural lethal case in a fattening calf, and an acute symptomatic case in a beef cow. In all cases, SHUV was confirmed by complete or partial viral genome sequencing. There is a significant difference of M and L segments of the novel strains compared with those of all known SHUV strains, while the S segments have more than 99% nucleotide (nt) identity with Israeli and African "Israeli-like" strains previously circulated in 2014-2019. This indicates a reassortment origin of the strain. At the same time, M and S segment nt sequences showed about 98-99% nt identity with some South African strains collected in 2016-2018. Nevertheless, the viral origin and the geographical place of the reassortment stayed unknown.
RESUMO
Reassortment contributes to the evolution of RNA viruses with segmented genomes, including Bluetongue virus (BTV). Recently, co-circulation of natural and vaccine BTV variants in Europe, and their ensuing reassortment, were proposed to promote appearance of novel European BTV strains, with potential implications for pathogenicity, spread and vaccination policies. Similarly, the geographical features of the Mediterranean basin, which spans over portions of three continents, may facilitate the appearance of clinically relevant reassortants via co-circulation of BTV strains of African, Asian and European origins. In August-October 2017, BTV serotype 6 (BTV-6) was identified in young animals exhibiting classical clinical signs of Bluetongue (BT) at Israeli sheep and cattle farms. Sequencing and pairwise analysis of this Israeli BTV-6 isolate revealed the closest sequence homology of its serotype-defining Segment 2 was with that of South African reference BTV-6 strain 5011 (93.88% identity). In contrast, the other viral segments showed highest homology (97.0%-99.47% identity) with BTV-3, -4 and -9 of Mediterranean and African origins. Specifically, four viral segments were nearly identical (99.13%-99.47%), with Tunisian and Italian BTV-3 strains (TUN2016 and SAD2018, correspondingly). Together, our data suggest that Mediterranean co-circulation and reassortment of BTV-3 and BTV-6 drove the emergence of a novel and virulent BTV-6 strain.
