Orbivirus Infections: Vector-Borne Transmission, Host Interactions, and Disease Control

Abstract

Orbiviruses are arthropod-borne viruses (arboviruses) belonging to the genus Orbivirus within the family Sedoreoviridae. These non-enveloped, icosahedral viruses possess a segmented double-stranded RNA (dsRNA) genome consisting of 10 linear segments, encoding seven structural (VP1–VP7) and five non-structural proteins (NS1–NS5). Transmission occurs primarily via hematophagous vectors, including Culicoides midges, mosquitoes, and ticks, affecting a wide range of vertebrate hosts. Notable pathogenic orbiviruses include Bluetongue virus (BTV), African horse sickness virus (AHSV), and Epizootic hemorrhagic disease virus (EHDV), which cause significant veterinary and economic impacts. Orbiviruses exhibit global distribution, with endemicity in regions like East Africa, where high seroprevalence has been reported in livestock. The virus replicates in the cytoplasm, forming viral inclusion bodies (VIBs), and evades host immune responses through antigenic variation and reassortment. Key structural proteins, such as VP2 and VP5, determine serotype specificity and host cell attachment, while VP7 aids in classification. Orbiviruses are highly stable due to their non-enveloped structure, resisting environmental degradation. Despite advancements in diagnostics and vaccine development, challenges remain in controlling outbreaks due to vector dynamics and genetic diversity. This review highlights orbivirus biology, transmission, pathogenesis, and molecular characteristics, emphasizing their veterinary importance and the need for continued research into improved vaccines and surveillance strategies.