Resident Atlantic Veterinary College Charlottetown, Prince Edward Island, Canada
Abstract:
Background: Equine arteritis virus (EAV) causes respiratory disease, abortion, neonatal death and persistent venereal transmission. A 2023 EAV outbreak in Prince Edward Island (PEI) Canada, marked by fatal fulminant interstitial pneumonia in foals, suggests recent introduction of EAV into a semi-naive regional Standardbred subpopulation within an otherwise endemic breed.
Objectives: To investigate the source and spread of EAV in the Standardbred broodmare and stallion population in PEI.
Animals: Standardbred breeding horses in PEI.
Methods: Cross-sectional surveillance was conducted during 2023-2025. Serum neutralization was used to detect EAV antibodies, and semen real-time PCR performed to assess viral shedding. Breeding histories and movement patterns were reconstructed using Standardbred Canada TrackIT records and on-farm interviews.
Results: A total of 417 horses were tested across 52 farms (mean 8/farm, range 1-57) with an overall seroprevalence of 49%. Farm level seroprevalence ranged from 0-100% (median 50%, IQR 3-67%). Among 31 stallions tested, seroprevalence was 42%, with five confirmed carriers and two persistently semen-shedding on follow-up. Epidemiologic links to high seroprevalence farms included housing carrier stallions, inadequate biosecurity, EAV-associated neonatal deaths, and breeding to carrier stallions.
Conclusions and Clinical Importance: The recent outbreak and wide range of seropositivity among PEI Standardbred farms suggests that EAV was newly introduced by a carrier stallion into a previously semi-naive population. These findings, in the context of EAV's endemicity in the wider Standardbred metapopulation, highlight the need for ongoing stallion surveillance, EAV genotyping, targeted vaccination, and rigorous biosecurity to limit further transmission and establishment.
