What is Equine Viral Artiritis?
First recognized in 1957 as a diagnostic disease, it is not pinkeye or influenza. Traits of the disease are abortion in pregnant mares and an infection of the respiratory tract. (1)
The disease is spread through inhalation of droplets containing infected material, such as sneezing, or direct contact with contamination, and ingestion of contaminated materials.
Herds of horses are easily infected due to saliva, nasal secretions, semen and blood being spread around by contaminated horses.
Necropsy of contaminated foals shows large amounts of the virus in the tissues.
At the onset of the disease, the horse will come down with a fever, 102F - 106F and begin a watery discharge from the nose. Excessive tearing of the eyes, inflamed eyelids due to conjunctivitis, and nasal congestion are also noted. Lab results show a lowered white blood cell count. (2)
Other symptoms include difficulty breathing, loss of appetite, weakness, depression, colic, coughing, diarrhea and edema of legs and eyelids. Petechial hemorrhages can appear on the inner surface of the eyelids and the nasal mucous membranes. (3)
These symptoms can persist for up to 2 weeks, but the edema may continue longer.
If the mare is pregnant, the abortion usually happens in the late stages of the disease or in the early recovery period. This is generally 12 to 30 days after initial exposure.
The abortion can be spontaneous, without forewarning, and the abortion rate is approximately 50%, due EVA.
Bacterial infections can occur along with the EVA, causing secondary complications, such as pneumonia. (4)
A veterinarian will request laboratory testing to confirm EVA, as external signs alone cannot indicate the disease, since it is similar to other respiratory illnesses. Slides will show the presence of the specific virus.
The disease causes a specific type of damage to the arteries, hence the name, "arteritis."
Though it is not seen by the naked eye, a degeneration of the middle layer of the arterial wall occurs, especially in smaller arteries. Depending on the extent of arterial damage, blood clots and hemorrhages can also occur. (5)
Autopsies can reveal the extent and type of damage that has occurred in the horse.
Veterinarians will recommend complete stall rest for several weeks after the symptoms of the disease have subsided. Good feed, clean hay, and lots and lots of fresh water are on the recovery menu, as is a comfortable, warm and draft-free stall.
A round of antibiotics can be prescribed for a period of time, to either prevent or combat secondary bacterial infections.
Work for the horse can only be resumed slowly, after this extended recovery period.
The horse is able to make this sound recovery, only if the disease was treated properly, and there were no serious side complications.
EVA is a serious, acute infection. Call the Vet.
Though few horses actually die from the disease, many foals do die, as a result of abortion.
Animals that were affected severely due to EVA may continue to have problems with impaired circulation or weakness, after recovery, due to residual arterial damage caused by the disease.
There is an effective vaccine available to horse owners on the market.
The aforementioned article is meant as a guideline and not Veterinary analysis. Quarantine your horse and call the Vet if you suspect your horse has EVA.
Closing with the immortal words of Roy Rogers and Dale Evans, "Happy Trails to You."
1- 5: "Horseman’s Veterinary Encyclopedia," by Will A. Hadden III, DVM