Emergence of a Novel Reassortant Strain of Bluetongue Serotype 6 in Israel, 2017: Clinical Manifestations of the Disease and Molecular Characterization.

Natalia Golender,Ily Shlamovitz,Itay Assis,Velizar Y Bumbarov,Benny Sharir,Joseph Seffi Varsano,Gabriel Kenigswald,Erez Yonay,Itzik Abramovitz,Avi Eldar,Shachar Ertracht,Yevgeny Khinich,Eitan Tiomkin,Marcelo Ehrlich

doi:10.3390/v11070633

Natalia Golender, Ily Shlamovitz + Show 12 more

Open Access

https://doi.org/10.3390/v11070633

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Journal: Viruses	Publication Date: Jul 10, 2019
Citations: 12	License type: CC BY 4.0

Affiliation: Hachaklait (Israel), Indi-Vet (Israel), Tel Aviv University

Abstract

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

Highlights

Bluetongue (BT) is an arthropode-born disease of domestic and wild ruminants caused by the Bluetongue virus (BTV) [1,2]
Prior to the present study, there was a lack of information about the clinical manifestation of the disease in local Israeli sheep caused by BTV serotype 6 (BTV-6)
This is in sharp contrast to the recent Israeli BTV-6 outbreak, which quickly spread through Israel causing heavy BT clinical manifestations both in sheep and in cattle

Summary

Introduction

Bluetongue (BT) is an arthropode-born disease of domestic and wild ruminants caused by the Bluetongue virus (BTV) [1,2]. BTV infection in cattle is usually asymptomatic, it appears that some strains are more pathogenic and are able to induce a clinical disease. In 2008, a reassortant live vaccine strain of BTV-6 was observed to induce clinical symptoms in cows in the Netherlands [23] These observed cases support the notion of the pathogenic potential of BTV-6 in cattle, as well as serving as a cautionary tale of the putative influence of anthropogenic factors in the spread of BTV [2]. Respectively) and quickly spread throughout the Golan Heights and the central areas of the country This outbreak was characterized by classical clinical manifestations of the disease and death in sheep and cattle. The present paper describes the clinical outcomes of BTV-6 infection in Israeli sheep and cattle herds, along with the genetic characterization and phylogenetic analysis of this recently identified. The novel genetic features of this novel strain, and their correlation with observed clinical symptoms, suggest an ever increasing significance of BTV-6 as a pathogen for domestic ruminants

Materials and Methods

Pan-BTV qRT-PCR

BTV Serotype Identification

Sequencing and Phylogenetic Analysis

Clinical Signs in Sheep and Cattle Naturally Infected with BTV-6

Phylogenetic analysis of Israeli

Discussion