Infectious diseases

IN THIS SERIES, WE’RE COVERING DISEASES THAT CAN AFFECT THE EQUINE POPULATION; HOW TO SPOT THEM, MEASURES TO TAKE TO PROTECT HORSES IN YOUR CARE, AND HOW TO PREVENT TRANSMISSION. IN PART SIX WE TALK ABOUT EQUINE VIRAL ARTERITIS (EVA).

Equine Viral Arteritis (EVA) is a contagious disease caused by equine arteritis virus (EAV). While rarely life threatening to otherwise healthy adult horses, EVA can cause abortion in pregnant mares, death in young foals and render breeding stallions permanent carriers.

Many horses exposed to the virus will develop no signs of the disease; however, these horses can still transmit infection.

Fever and runny nose; lethargy and stiff movement swelling, most notably the legs, scrotum, sheath, mammary glands and above or around the eyes; loss of appetite; depression; conjunctivitis; skin rash, frequently localised on the head and neck, but can be generalised; abortion in pregnant mares; pneumonia and death in young foals.

• Direct transmission during natural covering. • By AI using semen from infected stallions or semen which has been contaminated

during collection or processing. NB the virus can survive in chilled and frozen semen. • By contact with aborted foetuses or other products after birth. • Via droplets from coughing and sneezing. • Indirectly through contaminated equipment or materials. • In utero – when a mare is infected in late pregnancy, the virus can pass across the placenta to her unborn foal.

The use of sound management practices can help prevent and control EVA. The main methods of prevention are through vaccination, particularly for stallions and teasers, and ensuring freedom from infection before breeding activities start.

Your vet will take blood samples for testing in a laboratory to detect the antibodies that the horse generates in response to infection with the virus.

Sexually mature colts or stallions infected with EAV may become long-term or permanent carriers, known as ‘shedders’. Carrier stallions may or may not have exhibited prior clinical signs of EVA and their fertility is not aff ected. The virus is stored in their reproductive organs and can be shed for weeks, months, years or even life.

Carrier stallions show no clinical signs, but they can infect mares. Therefore, it is paramount that stallions are tested as free from the disease before breeding. • Practise good biosecurity on your premises, especially if you’re involved in breeding. • Test all stallions, teasers and mares before breeding. • Vaccination is recommended for breeding stallions and teasers – talk to your vet for advice. Before vaccination horses must be confi rmed to be free from disease by blood testing and this result must be recorded in the passport together with all vaccinations. • Follow guidance on isolation and testing when importing horses.

If a horse is to be inseminated using imported semen, then it should be accompanied by a health certifi cate stating that the semen is taken from a stallion tested and proven negative to be a shedder for EVA.

For semen that comes from inside the UK, it is advisable to check the stallion’s EVA status.

Stop all breeding activities immediately, isolate the aff ected horse/s and notify your vet without delay. Contact the DEFRA Rural Services Helpline on 03000 200 301 and an Animal & Plant Health Agency (APHA) vet will investigate.

Laboratory diagnosis, through blood testing, is essential. Antibodies are usually present in the blood seven to 14 days after infection and remain present for the rest of the horse’s life.

This is classifi ed as an exotic notifi able disease so the AP A will let you know what you need to do and restrictions on movements are likely to be imposed. f A is confi rmed in a stallion, he will remain under breeding restrictions until the risk is mitigated, through castration, export or repeated tests showing that he no longer has the virus.

The stallion cannot be used for breeding except under licence from APHA until then.