Pathogen test
-
This RT-qPCR test detects the genome (RNA) to Equine Viral Arteritis (EVA) virus.
Sample
- 5 mL - blood - K3 EDTA blood
- 10 mL - semen - sterile tube
Turnaround time
- 2 to 5 working days
What is Equine Viral Arteritis?
- Equine viral arteritis (EVA) is an economically important viral disease of equids.
- Stallions can become long term carriers of the virus, and transmit it during breeding. Although carrier stallions can be bred if precautions are taken, the need to mate them with seropositive or vaccinated mares decreases their desirability as breeders.
- Acute illness also occurs in some horses. Although deaths are very rare in healthy adults, pregnant mares that become infected may abort, and very young foals may die of fulminating pneumonia and enteritis. Equine viral arteritis has recently increased in prevalence, possibly due to increased transportation of horses and semen.
Clinical signs
- Most EAV infections, especially those that occur in mares bred to long-term carriers, are asymptomatic.
- The clinical signs are generally more severe in old or very young animals, and in horses that are immunocompromised or in poor condition.
- Fulminant infections with severe interstitial pneumonia and/ or enteritis can be seen in foals up to a few months of age.
- Systemic illness also occurs in some adults. In adult horses, the clinical signs may include fever, depression, anorexia, limb edema (particularly in the hindlimbs), and dependent edema of the prepuce, scrotum, mammary gland and/or ventral body wall.
- Conjunctivitis, photophobia, periorbital or supraorbital edema and rhinitis can also be seen.
- Abortions or stillbirths can occur in mares that are pregnant when they are exposed. Abortions are not necessarily preceded by systemic signs.
- Temporary decreases in fertility, including reduced quality sperm and decreased libido, may be seen in stallions during the acute stage of the disease.
Transmission
- Equine Arteritis Virus (EAV) can be transmitted by the respiratory and the venereal routes.
- Acutely affected horses excrete the virus in respiratory secretions; aerosol transmission is common when horses are gathered at racetracks, sales, shows and other events.
- This virus has also been found in urine and feces during the acute stage.
- It occurs in the reproductive tract of acutely infected mares, and both acutely and chronically infected stallions.
- In mares, EAV can be found in vaginal and uterine secretions, as well as in the ovary and oviduct, for a short period after infection.
- Mares infected late in pregnancy may give birth to infected foals.
- Stallions shed EAV in semen, and can carry the virus for years. Transmission from stallions can occur by natural service or artificial insemination.
- Some carriers may eventually clear the infection.
- True carrier states have not been reported in mares, geldings or sexually immature colts; however, EAV can occasionally be found for up to six months in the reproductive tract of older prepubertal colts.
- Equine arteritis virus can be transmitted on fomites including equipment, and may be spread mechanically by humans or animals.
- Semen remains infectious after freezing.
Prevention
- Acutely infected horses should be isolated to prevent transmission in secretions and excretions.
- Precautions should also be taken to avoid spreading the virus on fomites.
- EAV is readily inactivated by detergents, common disinfectants and lipid solvents.
- No specific treatment is available; however, most healthy horses other than young foals recover on their own.
- Good nursing and symptomatic treatment should be used in severe cases.
- Vaccination can also help contain outbreaks.
- Venereal transmission can be controlled by good management and vaccination.
- To protect pregnant mares from abortion, they should be separated from other horses and maintained in small groups according to their predicted foaling dates.
- Newly acquired horses should be isolated for 3 to 4 weeks.
- Vaccination appears to prevent uninfected stallions from becoming long term carriers.
- Stallions that are not carriers should be vaccinated before the start of the breeding season.
- Prepubertal colts are given the vaccine when they are 6-12 months old.
- Carrier stallions are identified and bred only to well vaccinated or naturally seropositive mares.
- Similarly, semen that contains EAV should be used only in these mares.
- Because first-time vaccinates may shed field viruses for a short time after exposure, these mares should be isolated from seronegative horses, particularly pregnant mares, for three weeks after breeding.
- Naturally infected mares and those that are not first-time vaccinates are isolated for 24-48 hours, to protect other horses from the viruses present in semen.
- Carrier stallions should be housed where they can be physically separated from uninfected horses; in one case, stallions apparently became infected by indirect exposure to semen. However, this appears to be rare.
- EAV is sensitive to sunlight and low humidity, and uninfected stallions have been kept near carriers for years without infection.
- Excellent hygiene and decontamination of fomites should be practiced when breeding infected horses or collecting semen.