Equine viral arteritis – vaccination protects

Equine viral arteritis (EVA) in horses, donkeys, and zebras is also known as horse morse, red fever, or pink eye. The main carriers are infected stallions, which continuously excrete the virus in their semen. Due to the typical inflammation of the blood vessels, it was given the name equine arteritis virus (EAV). The disease is notifiable.

INHALT
Transmission and origin Symptoms Diagnosis Treatment Forecast Prophylaxis
Transmission and origin

The EAV is mainly transmitted by infected stallions. They excrete the virus in their semen for weeks to years. During mating, they transmit it to mares. This leads to foal loss (abortion, miscarriage). Mares, geldings, foals, and stallions before sexual maturity go through an acute infection. They excrete the virus during the disease via nasal and eye secretions, saliva, and feces. Tissue from aborted fetuses, the afterbirth, and lochia (discharge after birth) are also virus-containing and contagious.

The EAV first multiplies in the macrophages (scavenger cells of the immune system) of the lungs. This is followed by infection of the vascular endothelium (innermost layer of the blood and lymph vessels). Damage to the endothelium leads to increased permeability of the vessels. This results in bleeding and edema (accumulation of fluid in the tissue).

Mating
The equine arteritis virus is transmitted during mating.
Symptoms

In most cases, EVA is asymptomatic. Edema occurs on the lower chest, lower abdomen, udder, and foreskin. Foals, poorly nourished or parasite-infested horses, and pregnant mares may develop high fever, severe respiratory disease with profuse nasal and ocular discharge, and colic symptoms. Pink eye, a severe conjunctivitis (inflammation of the conjunctiva), is typical. Stallions may experience reduced fertility. Infection of the fetus causes mares to miscarry between the third and tenth month of pregnancy or give birth to weak foals. The disease can be fatal in young foals.

Conjunctivitis
The typical pink eye in equine viral arteritis
Diagnosis

Following the preliminary report, your veterinary practice will carry out a general examination. If EVA is suspected, a nasopharyngeal or conjunctival swab or a blood sample will be taken. A semen sample will be examined in stallions. EAV can also be detected in the placenta and in miscarried fetuses.

Treatment

There are no medications specifically for EAV. The body fights the viruses itself. Rest and relaxation help support this process. Depending on the symptoms, your vet may recommend various treatments.

Forecast

In most cases, EVA causes no changes or only minor changes that are not life-threatening. After infection, horses are immune to EAV for years. The prognosis is poor for young foals, weakened horses, and fetuses.

Stallions that continuously shed EAV are excluded from breeding.

Prophylaxis

Vaccination of breeding stallions is the most effective preventive measure recognized worldwide. A vaccine against EAV is available in Germany. Vaccination does not prevent infection, but it does prevent the onset of symptoms such as foaling and reduces virus shedding.

Stallions intended for breeding should be vaccinated before reaching sexual maturity. This prevents them from becoming long-term carriers. Vaccination has no effect on virus shedding in stallions that are already permanently infected.

Horses can be vaccinated from the age of nine months. Two vaccinations at intervals of three to six weeks are required for basic immunization. The protective effect begins three weeks after the second vaccination. The EAV vaccination must be refreshed every six months. Vaccination during pregnancy is not recommended by the manufacturer. Your vet can send you a personalized vaccination schedule via petsXL. You will then automatically receive notifications when you need to make another appointment. The national semen regulation and the corresponding EU directive regulate the use of stallions in breeding. According to these regulations, stallions must be tested for antibodies against EAV at regular intervals. Positive animals must be tested for the virus in their semen.

It is not yet possible to distinguish between antibodies from vaccinated and infected horses. Some countries therefore prohibit the import of horses with EAV antibodies. Others require proof that the horse was free of EAV antibodies before the start of the basic immunization program.