Real-time RT-PCR for the detection and quantitative analysis of equine rhinitis viruses.
Authors: Quinlivan M, Maxwell G, Lyons P, Arkins S, Cullinane A
Journal: Equine veterinary journal
Summary
# Equine Rhinitis Virus Detection: A More Sensitive Diagnostic Tool Equine rhinitis viruses (ERV) are established causes of respiratory disease and performance loss in horses, yet their true prevalence has likely been obscured by the limited sensitivity of conventional diagnostic methods such as virus isolation. Quinlivan and colleagues developed and validated real-time reverse transcription PCR (rRT-PCR) assays targeting conserved regions of both ERV-A and ERV-B variants, testing over 400 samples from clinically affected and asymptomatic horses to establish diagnostic reliability. The resulting assays demonstrated detection limits of 10–100 genome copies—substantially more sensitive than traditional isolation methods—with archival data revealing annual incidence rates of approximately 10% for ERV-A and 1.5% for ERV-B across a seven-year surveillance period, plus notable co-circulation with equine influenza virus and unexpected detection in 29% of post-race urine samples. Practitioners can now employ these rRT-PCR assays for more accurate diagnosis and epidemiological tracking in individual horses and populations, enabling clearer investigation of temporal relationships between viral shedding and clinical signs. The superior sensitivity and reproducibility of this molecular approach suggests that ERV's economic impact on equine health and performance has indeed been underestimated, warranting reconsideration of its significance in respiratory disease investigations and competition fitness assessments.
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Practical Takeaways
- •Real-time RT-PCR is now a reliable diagnostic tool for rapid and sensitive detection of equine rhinitis viruses in clinical practice, enabling earlier diagnosis than traditional culture methods
- •Post-race urine testing can identify ERAV shedding in horses without clinical signs, suggesting subclinical viral circulation may be more common than previously recognized and could impact performance
- •The ability to detect both ERAV and ERBV simultaneously allows practitioners to monitor for co-infections with EIV and track viral epidemiology in individual yards or populations
Key Findings
- •Real-time RT-PCR assays achieved detection limits of 10-100 genome copies for both ERAV and ERBV, superior to virus isolation methods
- •Among 250 archival nasal swabs over 7 years, ERAV positive rate was 10% annually while ERBV was 1.5% annually
- •29 of 100 post-race urine samples tested positive for ERAV by rRT-PCR, indicating significant viral shedding in performance horses
- •Evidence of co-circulation between ERV variants and equine influenza virus (EIV) was documented