Abstract
Equine infectious anemia virus (EIAV) is a persistent lentivirus that causes equine infectious anemia (EIA). In Brazil, EIAV is endemic in the Pantanal region, and euthanasia is not mandatory in this area. All of the complete genomic sequences from field viruses are from North America, Asia, and Europe, and only proviral genomic sequences are available. Sequences from Brazilian EIAV are currently available only for gag and LTR regions. Thus, the present study aimed for the first time to sequence the entire EIAV genomic RNA in naturally infected horses from an endemic area in Brazil. RNA in plasma from naturally infected horses was used for next-generation sequencing (NGS), and gaps were filled using Sanger sequencing methodology. Complete viral genomes of EIAV from two horses were obtained and annotated (Access Number: MN560970 and MN560971). Putative genes were analyzed and compared with previously described genes, showing conservation in gag and pol genes and high variations in LTR and env sequences. Amino acid changes were identified in the p26 protein, one of the most common targets used for diagnosis, and p26 molecular modelling showed surface amino acid alterations in some epitopes. Brazilian genome sequences presented 88.6% nucleotide identity with one another and 75.8 to 77.3% with main field strains, such as EIAV Liaoning, Wyoming, Ireland, and Italy isolates. Furthermore, phylogenetic analysis suggested that this Brazilian strain comprises a separate monophyletic group. These results may help to better characterize EIAV and to overcome the challenges of diagnosing and controlling EIA in endemic regions.
Highlights
Equine infectious anemia virus (EIAV) is a lentivirus with an almost worldwide distribution that infects equids, such as horses, mules, and donkeys
EIAV has a single-stranded RNA genome of approximately 8.2 kb and contains three major genes, gag, pol, and env, which are flanked by long terminal repeats (LTRs)
Plasma from two horses (BRA1 and BRA2) from Poconé, MT, Brazil, was collected for this study, both were positive for EAIV according to agar gel immunodiffusion (AGID) [21] and enzyme-linked immunosorbent assay (ELISA) [22] tests
Summary
Equine infectious anemia virus (EIAV) is a lentivirus with an almost worldwide distribution that infects equids, such as horses, mules, and donkeys. Viruses 2020, 12, 207 by recurring febrile episodes associated with viremia, fever, thrombocytopaenia, and wasting clinical signs. Most animals progress from a chronic stage characterized by recurring peaks of viremia and fever to an asymptomatic stage of infection, and asymptomatic carriers remain infective for life. Equine infectious anemia (EIA) is transmitted by blood-sucking insects, mainly horseflies and stable flies, as well as by contaminated syringes and needles, blood-contaminated instruments, and contaminated blood used in transfusions. EIAV is a complex lentivirus and encodes three accessory genes: tat, rev, and S2 [1,2]
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