Evidence of equine influenza A (H3N8) activity in horses from Eastern and Central Saudi Arabia: 2013-2015.
Authors: Hemida M G, Perera R A P M, Chu D K W, Alnaeem A A, Peiris M
Journal: Equine veterinary journal
Summary
# Editorial Summary: Equine Influenza A (H3N8) Circulation in Saudi Arabia Equine influenza remains a significant respiratory pathogen globally, yet its epidemiology across the Middle East remains poorly characterised; this cross-sectional study addressed that knowledge gap by investigating H3N8 prevalence in unvaccinated horse populations across Eastern and Central Saudi Arabia between 2013 and 2015. Researchers collected 145 serum samples alongside 323 paired nasal and rectal swabs from horses in six major cities, employing ELISA and haemagglutination inhibition testing on sera and RT-qPCR on mucosal swabs to detect both current infection and prior exposure. Serological evidence of H3N8 exposure was substantial—81 horses (55.9%) tested ELISA-positive and 98 (67.6%) showed haemagglutination inhibition antibodies—yet notably, no viral RNA was detected in any respiratory or rectal swabs, suggesting prior infection rather than active circulation at the time of sampling. For equine practitioners in the region, these findings establish H3N8 as an endemic pathogen that warrants inclusion in differential diagnoses for respiratory disease and highlight the potential value of vaccination programmes in populations currently lacking immunological protection; the absence of sequenced virus isolates, however, limits understanding of which global H3N8 lineage(s) are circulating and their relationship to vaccine strain compatibility.
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Practical Takeaways
- •Consider equine influenza H3N8 as a differential diagnosis when investigating respiratory disease in horses in Saudi Arabia, particularly in unvaccinated populations
- •The high seroprevalence (55.9-67.6%) indicates widespread exposure to EIV H3N8 in the region, suggesting endemic circulation
- •Vaccination against EIV H3N8 should be considered for horses in Eastern and Central Saudi Arabia to reduce disease incidence
Key Findings
- •55.9% of sera (81/145) tested positive for influenza A antibodies by ELISA in Eastern and Central Saudi Arabia
- •67.6% of sera (98/145) tested positive for equine H3 by haemagglutination inhibition assay
- •No active viral RNA detected in 323 nasal and 323 rectal swabs by RT-qPCR
- •EIV H3N8 is circulating in Saudi Arabian horse populations despite no vaccination programs