Characterization of bluetongue virus serotype 28

Abstract

Bluetongue virus (Reoviridae; Orbivirus, BTV), which is usually transmitted by biting midges, affects wild and domestic ruminants worldwide, thereby causing an economically important disease. Recently, a putative new BTV strain was isolated from contaminated vaccine batches. In this study, we investigated the genomic and clinical characteristics of this isolate, provisionally designated BTV‐28. Phylogenetic analysis of BTV‐28 segment 2 (Seg‐2) showed that it is related to Seg‐2 from BTV serotypes 4, 10, 11, 17, 20 and 24, sharing 64%–66% identity in nucleotide sequences (nt) and 59%–62% in amino acid (aa) sequences of BTV VP2. BTV‐28 Seg‐6 is related to the newly reported XJ1407 BTV isolate, sharing 76.70% nt and 90.87% aa sequence identity. Seg‐5 was most closely related to a South African BTV‐4 strain, and all other segments showed close similarity to BTV‐26. Experimental infection by injection of 6‐month‐old ewes caused clinical signs in all injected animals, lasting from 2 to 3 days to several weeks post‐infection, including high body temperature, conjunctivitis, nasal discharge and rhinitis, facial oedema, oral hyperaemia, coronitis, cough, depression and tongue cyanosis. Naïve control animals, placed together with the infected sheep, displayed clinical signs and were positive for viral RNA, but their acute disease phase was shorter than that of BTV‐injected ewes. Control animals that were kept in a separated pen did not display any clinical signs and were negative for viral RNA presence throughout the experiment. Seroconversion was observed in the injected and in one of the two contact‐infected animals. These findings demonstrate that BTV‐28 infection of sheep can result in clinical manifestation, and the clinical signs detected in the contact animals suggest that it might be directly transmitted between the mammalian hosts.

Identification and Characterization of Bluetongue Virus Serotype 14 in Russia

“…Unfortunately, data on the extent of its use in the farming industry are not available. In addition, contaminated serum or other components may have been used to produce other live vaccines for cattle or small ruminants, which have already shown potential for contamination with BTV, as reported for a sheeppox vaccine (16). Following vaccination, the contaminating BTV can escape and begin to circulate in the field.…”

“…The BTV-14 genome was detected in all blood samples of infected animals, as well as in the samples of infected chicken embryos and cell cultures that previously tested positive by universal real-time RT-PCR based on the NS3 protein. In the serotype-specific RT-PCR testing, the results were negative for BTV 1,2,4,6,8,9,11,and 16. Thus, the virus isolated from the infected animals in the Smolensk region was identified as serotype 14 of BTV.…”

“…Ticks have also been implicated as a vector (9). A total of 27 serotypes were recently recognized, with another few pending (10)(11)(12)(13)(14)(15)(16). The serotypes exhibit various patterns of transmission, including direct contact (17,18), which contradicts the accepted concept that bluetongue virus (BTV) is only transferred via a Culicoides vector (19).…”

Bluetongue Serotype 3 in Israel 2013–2018: Clinical Manifestations of the Disease and Molecular Characterization of Israeli Strains

“…BTV is a double-stranded (ds) RNA virus (3), its genome consists of ten segments (Seg-1 to Seg-10) of linear dsRNA coding 7 structural (VP1-VP7) and 5 non-structural (NS1, NS2, NS3/NS3a, NS4, and NS5) proteins (4) At present twenty-eighth distinct BTV serotypes have been officially recognized based on Seg-2 gene sequence (5,6). Other putative novel BTV serotypes have also been described (7)(8)(9)(10)(11).…”

“…Even though they don't seem to be epidemiologically important, vertical and horizontal transmissions have also been described (15)(16)(17)(18). For BTV-26, BTV-27 v02 and, probably, BTV-X ITL2015 and BTV-28 transmission by direct contact has been demonstrated or hypothesized (6,10,19,20).…”