Coding-complete genome sequences of group B equine rotavirus from central Kentucky, USA, reveal circulation of a single genome constellation.

Coding-complete genome sequencing of equine rotavirus B strains from central Kentucky shows that a single, highly conserved genome constellation has been circulating among foals since 2021, indicating genetic stability of the virus in this region.

Background and Purpose

• Equine rotavirus B (ERVB) is a viral pathogen causing diarrhea in foals.
• Outbreaks in central Kentucky began in 2021, raising concerns about the nature and evolution of the virus.
• The study aimed to characterize the genetic makeup of ERVB strains circulating in the region during 2024.
• Understanding the genome sequences helps assess viral diversity, evolution, and potential vaccine or therapeutic targets.

Methods

• Samples were collected from foals diagnosed with ERVB diarrhea in central Kentucky.
• Complete coding genome sequences of 14 ERVB strains from 2024 were obtained, ensuring comprehensive genetic analysis.
• Sequence data were compared against the 2021 prototype ERVB strain from the same region (RVB/Horse-wt/USA/KY1518/2021).
• Genomic constellation— the combination and arrangement of gene segments in the virus genome—was determined to identify patterns of genetic variation or conservation.

Findings

• All 14 ERVB strains from 2024 exhibited greater than 99% nucleotide identity to the 2021 prototype strain, indicating minimal genetic drift or variation over three years.
• The genome constellation was conserved among all strains, identified as G3-P[3]-I3-R3-C3-M3-A4-N3-T3-E3-H3. Each letter-number set corresponds to specific viral gene segments, showing that their type and organization have remained stable.
• This conservation suggests a single lineage of ERVB is responsible for the ongoing infections in central Kentucky.

Significance and Implications

• The genetic stability of ERVB over multiple years implies limited evolutionary pressure or successful adaptation to the equine host environment in this region.
• Consistency in viral genome simplifies efforts in diagnostic testing since assays developed for the 2021 strain remain relevant.
• Understanding the conserved genome constellation can inform vaccine development by targeting stable viral proteins, potentially enhancing vaccine efficacy.
• Tracking this stable lineage helps veterinarians and researchers monitor the epidemiology of ERVB and may assist in controlling the spread of foal diarrhea outbreaks.