Molecular epidemiology of the African horse sickness virus S10 gene.

The research article investigates the molecular epidemiology of the S10 gene from 145 isolates of African horse sickness viruses, finding that the S10 gene varies among different serotypes and plays a significant role in tracing and understanding the outbreaks of African horse sickness.

Objective of the study

• The aim of this study was to investigate the molecular epidemiology of the African horse sickness virus (AHSV) by examining the S10 gene in samples of AHSV isolated from horses in South Africa.
• The researchers wanted to determine the phylogeny of the virus, assess the level of clade variance amongst the serotypes and ascertain the role of the S10 gene in tracing AHSV outbreaks.

Methodology

• The researchers isolated AHSV from blood and organ samples submitted to the Faculty of Veterinary Science at the University of Pretoria from 2004 to 2006.
• All nine serotypes of the virus were represented in the study, with a range of 3 to 60 isolates per serotype.
• The team examined the S10 nucleotide sequences of these isolates and conducted a phylogenetic analysis.

Key Findings

• AHSV, bluetongue virus (BTV) and equine encephalosis virus (EEV) all formed monophyletic groups, with BTV being genetically closer to AHSV than EEV.
• The study established the presence of three distinct S10 phylogenetic clades: alpha, beta and gamma.
• Some serotypes were restricted to a single clade, while others fell into different clades, illustrating a varied distribution of the disease.
• A strong purifying selection was found, indicating a strong pressure to conserve the function of the protein encoded by the S10 gene.
• The S10 gene was shown to be highly variable and very useful in tracking the spread of AHSV, as illustrated by the analysis of an outbreak in 2004.

Conclusions and Implications

• The S10 gene was identified as the second most variable gene of the AHSV genome, making it a significant resource for molecular epidemiological investigations.
• The gene’s small size and conserved terminal regions facilitate easy and fast sequencing, enabling rapid response to AHSV outbreaks.
• Establishing a database of S10 sequences could substantially aid efforts to characterize future AHS outbreaks and contribute to broader knowledge about the epidemiology of the disease.