Equine viral arteritis is an infectious disease that affects horses and is generally associated with racetracks and breeding centers or reproduction of this species. Its origin, as its name indicates, is viral. The virus, in general, does not usually give serious forms and much less with high mortality, it is only usually more serious in certain age and risk groups. The clinical signs that will appear in horses will be fundamentally as a consequence of the inflammation in the smaller caliber blood vessels. The virus mainly targets the respiratory system and causes abortions in pregnant females.
In this article on our site we will discuss Equine Viral Arteritis, its symptoms, diagnosis and treatment. Keep reading to learn more about this disease that our horses can suffer from.
What is equine viral arteritis?
Equine viral arteritis (EVA) is an infectious and contagious disease that affects equids. It is caused by a virus that targets mainly the placenta or the respiratory system, causing abortions or inflammatory lesions in the arterioles of animals with acute infection.
Affects equids, but there is some evidence that alpacas and llamas may also be affected. It is a disease that is not transmitted to humans, that is, it is not a zoonosis.
Many of the cases of infection by this disease are subclinical, so they do not produce clinical signs, although it depends on the virulence of the strain. The most serious forms of the disease that can end the life of the horse usually occur in very young foals or colts with congenital disease, but also in immunosuppressed horses or with some other pathology.
Causes of equine viral arteritis
EVD is caused by an RNA virus, the equine arteritis virus (EAV), belonging to the genus Arterivirus, family Arteriviridae and order Nidovirales.
How is equine arteritis virus transmitted?
This virus is transmitted from respiratory secretions, fresh or frozen semen, placenta, fluids and aborted fetuses. That is, the two main forms of transmission are:
- Respiratory tract: by exudates and secretions when they cough or sneeze or leave secretions in feeders and drinkers. It is more important during the acute phase of the disease.
- Venereal route: during mating, when the stallion or mare is infected, as well as during artificial insemination.
The disease can also be transmitted congenitally from mother to offspring.
Equine viral arteritis symptoms
In the pathogenesis of equine viral arteritis, the virus multiplies in the arterioles, causing edema and cell death (necrosis). Clinical signs begin after 3-14 days of incubation, being earlier if the infection has been through the respiratory route and later if the transmission has occurred through the venereal route.
Once the disease develops, the clinical signs that may be observed are as follows:
- Fever.
- Depression.
- Anorexy.
- Mucous congestion.
- Petechiae.
- Conjunctivitis.
- Epiphora (tear secretion).
- Runny nose.
- Moderate cough.
- Dyspnoea.
- Stomatitis.
- Diarrhea.
- Colic.
- Urticaria.
- Edemas in the foreskin, scrotum or mammary gland.
- Perio or supraorbital edema.
- Edemas in distal areas, especially in the hind limbs.
- Abortions if there is massive fetal infection and placental necrosis.
Generally, horses shed the virus for 28 days after illness, but in mature males it shows a lot of persistence in the prostate and the seminal vesicles, making the period in which they are infectious can even last their entire lives.
What injuries does it cause to the organs of a sick horse?
The lesions that occur in the organs of horses show a clear injury to the blood vessels Specifically, disseminated vasculitis appears in smaller arterioles and venules that give rise to hemorrhages, congestion and edema, especially in the subcutaneous tissue of the abdomen and extremities, as well as peritoneal, pleural and pericardial fluid.
In foals killed by this virus, pulmonary edema, emphysema (air in the lung), interstitial pneumonia, enteritis, and spleen infarctions have been observed.
Diagnosis of equine viral arteritis
Given the presence of the clinical signs that we have discussed in horses, we must make a differential diagnosis among other pathologies that affect horses horses and can give rise to similar symptoms:
- Equine Influenza.
- Equine rhinopneumonitis.
- Equine adenovirus.
- Hemorrhagic purpura.
- Equine infectious anemia.
The blood test may show leukopenia (reduced total white blood cell count). The definitive diagnosis will be given by the laboratory. To do this, samples must be obtained to be sent to it and they can carry out the appropriate laboratory tests for diagnosis.
The samples must be obtained as soon as possible after the appearance of the peak of fever or when infection is suspected due to the appearance of clinical signs indicative of CVA, and they are:
- Unclotted blood and serum.
- Semen.
- Nasopharyngeal or deep nasal swabs.
- Conjunctival swabs.
- Tissues from the placenta, lungs, liver and lymphoreticular tissue of the aborted fetus.
When EAV-related abortions are suspected, detection and isolation of the virus should be done with fluids and tissues from the placenta, lungs, liver, and lymphoreticular tissues of the fetus.
The tests to perform depending on the type of sample are:
- ELISA.
- Seroneutralization.
- Complement fixation.
- RT-PCR.
- Virus isolation.
- Histopathology of arterioles.
Treatment and prevention of equine viral arteritis
The treatment of equine viral arteritis is only carried out in endemic areas of the disease (which have it) and is symptomatic with the use of antipyretics, anti-inflammatories and diuretics.
Proper control and prevention of the disease should always be carried out with a series of preventive measures. This seeks to reduce the spread of the virus in breeding horse populations to minimize the risk of abortions and deaths of young foals, as well as to establish carrier status in stallions and foals. The control measures are:
- Semen analysis prior to the entry of new stallions.
- Quarantine of the new stallions.
- Good management in equine reproduction centers.
- Identification of carrier horses.
- Isolate horses with clinical signs.
- Vaccination depending on the country.
Vaccine for equine viral arteritis
Vaccination is prohibited in Spain. However, the countries where it is possible to vaccinate have two types of vaccines available to control this disease, specifically:
- Modified Live Virus Vaccine: Safe and effective for males, female mares and foals. However, it should not be given to pregnant mares in their last two months of gestation and to foals less than 6 weeks old, unless there is a high risk of infection. It protects against EVA for between 1 and 3 years, but it does not prevent reinfection or virus replication. However, virus shedding via the nasopharyngeal route is significantly less than in horses that have not been vaccinated.
- Killed virus vaccine: safe in pregnant mares, but does not induce immunity as strong as the previous one, requiring two or more dose to achieve a good neutralizing antibody response.
It is advisable to vaccinate foals between 6 and 12 months of age before they are at risk of being infected by the virus.
