The affected horse participated in competitions in Kungsbacka on March 6–8 and in Laholm on March 8.
The virus can cause fever, respiratory symptoms, neurological symptoms and miscarriage – which is why it is commonly known as the abortion virus.
Now the Swedish Equestrian Federation and SVA are warning of the risk of infection to the hundreds of horses that participated in the competitions.
"If all horses that attended the competitions are kept isolated for 21 days, the spread of infection can be stopped. All horses in the stable that were in contact with horses that attended the competitions should also be quarantined during the observation period," says Gittan Gröndahl, state veterinarian at SVA, in a press release.
In the event of an elevated temperature or symptoms of illness, a veterinarian should be called and samples taken for EHV-1, she adds.
"If everyone does this correctly, there is a good chance that the spread of infection can be stopped."
No other horses that participated in the competitions have yet shown any symptoms.
