Serological surveillance of equine viral arteritis in the United Kingdom since the outbreak in 1993.

This is a study about the prevalence of equine arteritis virus (EAV), a contagious disease in horses, in the United Kingdom after an outbreak in 1993. The study found that, while significant percentages of standardbred horses tested positive for EAV, signs of the disease were not prevalent in those horses.

Study Summary

Blood samples from unvaccinated horses tested during 1995 and 1996 revealed a small percentage of horses were seropositive for EAV, meaning they had been infected in the past and developed antibodies against the virus. The study also identified specific horse breeds that showed higher EAV seroprevalence, with a higher prevalence identified amongst standardbred horses compared to thoroughbreds.

Testing and Results

• In 1995, 185 of 9203 unvaccinated horses (2.0 per cent) tested positive for EAV antibodies.
• In 1996, 46 of 8851 unvaccinated horses (0.52 per cent) tested positive.
• Among standardbred horses, 84 of 454 (18.5 per cent) were EAV seropositive.
• A difference in EAV seroprevalence existed within the standardbred breed, with the seropositive rate being 25% among non-racing horses and 41% among stallions.
• Besides, almost all the EAV seropositive stallions had been imported from North America or the European Union.
• Out of 34 seropositive stallions, nine (26.5%) were presumed to shed EAV in their semen. Among specific breeds, researchers found viral shedding in 40% of standardbreds and 33% of warmbloods.

Key Findings

Based on the tests, researchers concluded clinically inapparent EVA, i.e., horses were infected without showing symptoms, had occurred in the UK. This indicates a potential for an undercover spread of the virus in the horse population. The absence of typical EAV infection signs even in mares test mated to stallions shedding the virus suggested that the virus might not be causing the disease or the disease may be subclinical and undetected. These findings could have significant implications for shaping EAV surveillance strategies and controlling the spread of the virus.