Genetic disease in the horse
Authors: Graves Kathryn T.
Journal: Journal of Equine Veterinary Science
Summary
# Editorial Summary: Genetic disease in the horse African horse sickness virus (AHSV) presents a persistent biosecurity challenge to the equine industry, particularly for international trade, which is why WOAH maintains strict certification protocols for disease-free status. Graves evaluated the diagnostic reliability of two WOAH-recommended reverse-transcription quantitative PCR (RT-qPCR) assays using 150 confirmed AHSV-positive samples, finding that the Agüero method produced an 8.7% false-negative rate (13 missed samples) whilst the Guthrie method performed with acceptable sensitivity. Genetic variation in the AHSV VP7 gene—the viral target sequence—was identified as the cause of these detection failures, with mispriming or probe binding issues creating blind spots in virus identification. By incorporating sequence-informed modifications to both assays, a second round of testing achieved 100% sensitivity in both methods, demonstrating that the virus's natural genetic diversity can undermine molecular diagnostic accuracy. For practitioners involved in movement certification, export protocols or disease surveillance, this work underscores the critical importance of assay validation against contemporary viral populations and the need for regular protocol review—false negatives in AHSV testing carry significant consequences for herd health and international trade compliance.
Read the full abstract on PubMed
Practical Takeaways
- •If importing or certifying horses from sub-Saharan Africa, be aware that current RT-qPCR assays may have up to 8.7% false-negative rates; request updated assay methods or serial testing for critical animals
- •Diagnostic laboratories should validate molecular protocols against recent AHSV strains to ensure genetic variants aren't missed
- •For movement certification purposes, consider that a negative test may not guarantee absence of infection if outdated assay methods are used
Key Findings
- •The Agüero RT-qPCR assay had an 8.7% false-negative rate (13/150 samples) for AHSV detection due to genetic variability
- •Modified primer and probe sequences achieved 100% sensitivity for both assays in revised in vitro testing
- •Genetic variability in AHSV VP7 genes can cause mispriming and probe binding failures in molecular detection assays
- •Continuous monitoring and updating of WOAH-recommended molecular protocols is necessary to maintain diagnostic accuracy