EQUINE herpes virus is a common virus that occurs in horse populations worldwide. The two most common strains are EHV-1 which causes abortion, respiratory disease and paralysis and EHV-4 which usually causes respiratory disease only but can occasionally cause abortion.

A maiden filly arrived to the National Stud in Newmarket, from France, on January 20th and was found to have an EHV-1 infection. The virus was found in the filly while she was stabled at the isolation unit, which is one mile from the main stud.

The affected horse is a four-year-old vaccinated maiden and she exhibited the typical clinical signs of incoordination and bladder dysfunction.

EHV-1 can establish a latent infection where it persists in an inactive state but can reactivate under stress associated with, for example, pain or transport over long distances.

Although vaccination has been demonstrated to decrease the risk of EHV1 associated abortion none of the vaccines have a claim to protect against the neurological form of the disease.

Therefore the horse industry relies on rapid diagnosis and the implementation of the Code of Practice to control the disease. The Irish Thoroughbred Breeders Association (ITBA) Code of Practice has excellent information and advice, it can be downloaded at itba.info.

PREVENTION IS KEY

If we can significantly reduce the likelihood of such outbreaks in the first place, we then become less concerned with the consequences and the treatment. The main ways to prevent EHV infection are good management of breeding stock, good hygiene during breeding activities and vaccination.

EHV is transmitted through both direct and indirect contact with infected horses and can be easily spread via water buckets, feed buckets, tack, grooming equipment and even on the hands and feet of people caring for affected animals.

EHV is destroyed readily by heat and disinfectants. Stables, equipment and vehicles for horse transport should therefore be steam cleaned and disinfected regularly as a matter of routine.

I would recommend that horse owners use a multipurpose disinfectant like NuevoAgri that has been tested in approved labs in Ireland such as the Irish Equine Centre and Abbott Analytical in the UK. It has been proven to kill harmful pathogens such as StreptoccocusEqui (Strangles), Equine Herpes Virus, Salmonella and many other harmful pathogens. It conforms to the most stringent EU laws.

CLINICAL SIGNS

  • Signs of respiratory disease include mild fever, coughing and discharge from the nose.
  • Live foals infected in utero are usually abnormal from birth, showing weakness, jaundice, difficulty in breathing and occasionally nervous signs. They usually die within three days. The most common sign in older foals is a nasal discharge.
  • There are usually no warning signs of abortion caused by EHV.
  • Horses affected by paralytic EHV often display inco-ordination of the hind, and occasionally front, limbs, urine retention and, in severe cases, recumbency (lying down and unable to stand). These signs may be preceded by initial respiratory signs.

    • NB: All horses can be ‘carriers’ of the virus, meaning that they may transmit infection without showing signs of illness. In carriers, illness may become apparent from time to time, especially after stress or after suffering another disease.

    The virus is always contagious at this time. In late pregnant mares, prolonged transport and other types of stress may increase the risk of foetal infection.

    DIAGNOSIS

    Horse owners concerned about their animals should contact their veterinary clinician who will submit nasal swabs and bloods to the Irish Equine Centre. The Virology Unit at the Centre is an OIE (World Organisation for Animal Health) Reference Laboratory for EHV-1 and will process these samples free of charge.

    The laboratory testing carried out by the OIE Reference Laboratory is funded by the Department of Agriculture and the Marine.

    TREATMENT AND CONTROL

    Any necessary treatment will be determined by the attending veterinary surgeon.

    Any horse known or suspected to have EHV should not be sent to a stallion stud or to other premises where there are pregnant or brood mares.

    Maintain isolation, movement restrictions and hygiene measures for at least 28 days. Mares which have aborted must be kept in isolation from pregnant mares for 56 days after abortion.

    If paralytic EHV is confirmed, policy should be decided with the attending veterinary surgeon.

    Detailed advice on specific cases can be obtained from the Irish Equine Centre, or specialist equine veterinary practices.

    In all situations communication is extremely important. Failure to communicate can contribute to the spread of infection to the detriment of all owners and their horses, particularly mare owners.

    The owner/manager of the affected horse(s) or premises should inform the relevant breeders’ association, owner and staff et cetera.

    For further advice contact Jerry on 0874555356 or visit nuevoagri.ie.

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