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Equine flu: what horse owners need to know during the current outbreak in Britain

Carol Phillips — Thu, 21 May 2026 13:27:03 +0000

This article has been edited and approved by Karen Coumbe MRCVS, H&H’s veterinary advisor since 1991.

(Image credit: creditUnknown)

Equine flu, as equine influenza is commonly known, is caused by various strains of the influenza virus that affect the upper and lower respiratory tract of horses, donkeys and mules. It is a major and economically important cause of acute respiratory disease throughout the world, with the exception of some island nations, such as Iceland and New Zealand. As H&H’s veterinary advisor Karen Coumbe has said, “equine flu rarely kills horses, but it does kill horse events”.

There has been a significant increase in cases of equine flu in the British horse population since 1 April 2026. This has led to tighter biosecurity requirements at horse shows and other places where horses come together. Six-monthly vaccinations are being recommended with horses’ passports now being checked on arrival at many venues. The increase in cases is not inline with the normal pattern, which research published in the Equine Veterinary Journal has shown typically increases in the final quarter of the calendar year.

British Equestrian (BEF) is calling for “horse owners, yard managers and vets to adopt a risk-based approach when moving horses, particularly between premises, events and regions” during this outbreak. The BEF has also stated that France is also seeing heightened equine influenza activity, particularly in the north of the country, so advises using “extreme caution when travelling horses to, from or through there”. This also applies to purchasing horses from France.

View the latest data from the Equine Infectious Disease Surveillance website

What are the signs of equine flu?

A very high temperature of 39-41C (103-106F) which lasts for one to three days
A frequent harsh, dry cough that can last for several weeks
A clear, watery nasal discharge that may become thick and yellow or green
Enlarged glands under the lower jaw
Clear discharge from the eyes and redness around eyes
Depression and loss of appetite
Sometimes filling of the lower limbs, muscle stiffness and other signs such as weight loss

How do horses catch equine flu?

As with the human version, equine flu is very contagious. With an incubation period of one to five days, it spreads rapidly as the virus is released into the atmosphere by infected animals. It is mainly acquired through inhalation of virus from ill animals coughing and spluttering infected respiratory droplets. Indirect spread is also possible via buckets or grooms/handlers/nurses/vets.

Unlike strangles and some other infections, the flu virus does not linger nor survive for long outside the horse, but it can be airborne, blowing over surprisingly long distances, certainly more than 1km.

Once the virus has been inhaled, it invades the lining (epithelium) of the horse’s airway, which becomes inflamed, producing a very sore throat and a nasty cough. This damage causes patches of the membranes lining the airways to ulcerate, which disrupts the clearance of mucus and debris from the airways causing a thick discharge from the horse’s nose. Bacteria then invade the damaged areas leading to further infections.

How serious is equine flu: do I need to call the vet?

If your horse shows a raised temperature and/or any signs of equine influenza, strict hygiene and isolation procedures should be adhered to immediately and you should contact your vet.

Horses that have been in contact with an affected animal should be carefully monitored and should not attend shows or external clinics or training.

It is recommended that horses on a stable yard with an outbreak of equine flu do not leave the premises while the outbreak is ongoing.

Diagnosis of equine flu

An accurate diagnosis of equine flu can be made by:

recognising the clinical signs and the history of rapid spread between horses
isolation of the virus through nasal or nasopharyngeal swabs
rising antibody levels in blood (serum) samples taken early in the course of the disease and two to three weeks later
history of recent contact with a confirmed case of the disease

Vaccinated horses may still show signs, but these are usually much milder than those seen in unvaccinated horses.

Equine flu treatment

Basic nursing is key when treating a horse with the virus. Good stable ventilation and dust-free management is essential. Exposure to dust should be minimised, as horses with respiratory infections are more susceptible to airway irritation. It is best to switch to dust-free bedding and feed soaked hay, or better still haylage, from the floor.

If weather permits and risks to other animals are manageable, then affected horses benefit from being turned out for at least part of the day once their temperatures have returned to normal. This is especially important in the recovery stages. At the same time infected horses should be isolated.

Antibiotics have no effect against a virus, but can be useful to control secondary bacterial invasion. This is a risk in foals or elderly or otherwise unwell animals, which can succumb to fatal pneumonia. Medications to help breathing can prove beneficial.

How long does equine flu last?

Horses that catch equine flu typically start to show signs around one to five days after exposure and it may take three to six weeks before the signs pass, assuming they are receive appropriate care.

Horses with a respiratory infection should be given complete rest and not restart any strenuous exercise until at least three to four weeks after the signs have gone.

How to prevent flu in horses

Flu is difficult to control, especially in equine that are frequently transported and mixed extensively, so regular vaccination of horses is important. Equine flu outbreaks are most common when young susceptible horses are brought together at sales and shows, or for weaning and training.

Surprisingly low numbers of the UK’s horse population are vaccinated, despite the fact that vaccination is the preferred method of control and is compulsory when competing under British Horseracing Authority, FEI and affiliated governing bodies’ rules in the UK.

Whenever you attend shows or training outings away from home, you should follow strict biosecurity and hygiene methods such as:

Do not allow horses to touch or sniff other horses
Riders/grooms should only handle their own horses and tack
Do not share buckets or kit with other horses/riders
Avoid using on-site water facilities. If this is impossible, avoid placing the hose into the bucket and sanitise your hands before carrying the bucket to the horse
Avoid hand grazing your horse at a venue
Ensure show stables have been disinfected before and after use and all bedding removed and replaced with fresh
Horse’s temperature should be taken before travel to an external venue
Horses returning from external venues should be isolated if possible, with their temperature and their health closely monitored

How often are horses vaccinated for flu?

All British equine sport governing bodies require the minimum of the first two vaccines to have been given prior to attending competition.

The British Horseracing Authority introduced new flu vaccination rules on 1 January 2022 to harmonise with other racing authorities in Europe. The new rules increased the frequency of boosters from 12 months to six months and reduced the time periods between the first and second vaccines from 21-92 days to 21-60 days, and between the second and third vaccines from 150-215 days to 120-180 days.

NB: We recommend all competition riders double check the latest version of the appropriate rulebook to ensure your horse’s vaccinations comply with their governing body’s requirements.

British Horseracing Authority: horses must have been vaccinated against equine flu within the past six months. Horses must not have been vaccinated less than seven days before racing.FEI competitions: a booster vaccination must have been given no more than six months and 21 days prior to competing. A vaccination should not have been given within seven days of the competition or of entry into the FEI stables.British Dressage (BD): Once a horse has received its first three vaccinations, further vaccinations can be given at 12 monthly intervals, but not within seven days of competing. In response to the spring 2026 outbreaks, BD is “strongly recommending that all members move to a six-month vaccination cycle”. If your horse’s last vaccination was more than six months ago, BD recommends “that you bring their annual booster forward to provide sufficient cover when competing during the summer season”.British Eventing (BE): Horses require an annual booster every 12 months for national BE competitions, since 1 January 2026. A horse may not compete if it has been given the booster on any of the seven days before it is to compete at an event. Although six monthly boosters are not mandated by BE, the organisation strongly advises that horse owners and competitors give horses an additional booster at this time of high risk if they were last vaccinated more than six months previously.British Showjumping (BS): Horses to have received booster vaccinations not more than 365 days from their last vaccination, and should not compete within seven days of receiving a vaccination. In response to the spring 2026 outbreaks, BS venues will be carrying out passport checks on arrival. BS has shared the Equine Infectious Disease Action Group’s recommendation that owners whose horses were last vaccinated more than six months ago, are strongly recommended to bring their next booster forwards to give them the best protection during the outbreak.British Riding Clubs (BRC): Horses must have had their initial course, plus annual (12 month) vaccinations to attend BRC qualifiers and/or championships.

If a horse or pony is competing in one discipline for instance, showjumping but it is attending an event at a venue, such as a racecourse, it will be required to comply with the vaccination requirements under the rules of racing, which means it must have been vaccinated within six month, but not in the previous seven days.

The British Horseracing Authority has stated that, from Wednesday 20 May 2026, only horses from licensed training yards will be allowed to enter racecourses on racedays. This means all scheduled hunter chases from 20 May have been called off and Retraining of Racehorses (RoR) parades are cancelled. Racecourses are also increasing the period of time between hosting an equine event involving horses from unlicensed premises and a licensed raceday to six clear days (from three).

The vaccination record(s) in the horse’s passport, must be completed, signed and stamped line by line, by an appropriate veterinary surgeon (who is neither the owner nor the rider of the horse). The responsibility to comply with this rule lies with the owner, who should consult with their vet.

From 1 January 2026, for horses competing under FEI rules, flu vaccinations must be recorded digitally in the FEI HorseApp, as well as in the horse’s passport. Vets must enter the vaccination details on the day it is administered. There is a transition period running until 30 June 2026 during which no sanctions will be issued, but from 1 July 2026 missing or incorrect digital records may result in fines for the person responsible (this is usually the horse’s rider).

What to do during an equine flu outbreak?

If flu occurs locally, it may be advisable to give a booster vaccination to any healthy horse that has not been vaccinated in the previous six months. Consult your vet for advice.

The BEF explains that “frequent boosters ensure antibody levels remain high, which is essential for reducing both the severity of the disease and risk of the virus shedding within the wider equine population”.

You may wish to limit the situations where you expose your horse to others by reducing the competitions and training outings you attend, or choose only to visit venues that actively check the vaccination status of equines in attendance and require six-monthly boosters.

Can humans catch equine flu?

The equine influenza virus is similar to the flu virus that affects people, but is not identical, so horses cannot catch human influenza or vice versa.

References and further reading

What happened after the epidemic? Equine influenza surveillance sheds light on sources and seasonal risk in the United Kingdom Equine Veterinary Journal, 5 March 2026

British Dressage’s equine influenza update, British Dressage website, 20 May 2026

British Showjumping’s equine influenza update, British Showjumping website, 21 May 2026

British Eventing’s equine influenza update, British Eventing website, 21 May 2026

Call for increased vigilance as number of reported equine influenza outbreaks in UK continues to rise, British Equestrian website, 12 May 2026

Annual booster vaccination and the risk of equine influenza to Thoroughbred racehorses Equine veterinary journal, 21 November 2019

British Horseracing Authority: amendments to the vaccines code, October 2021

British Riding Clubs Important Flu Vaccination Update, 21 October 2022

British Eventing vaccination update, British Eventing Facebook page, 15 December 2025

Mandatory registration of equine influenza vaccination details in the FEI HorseApp, FEI website, 12 Dec 2025

For unlimited access to expert advice on how best to care for your horse, subscribe to the Horse & Hound website

Feather mites in horses (heel/chorioptic mange) is a challenging problem for owners

Carol Phillips — Tue, 27 Jan 2026 14:56:25 +0000

This article has been edited and approved by Karen Coumbe MRCVS, H&H’s veterinary advisor since 1991.

(Image credit: creditUnknown)

Feather mites in horses are among the most stubborn of equine parasites, causing a condition commonly called heel mange (chorioptic mange). The condition typically affects heavily feathered breeds such as traditional cobs, Shires, Clydesdales and Friesians, and some native ponies.

When severely affected, horses with an infestation will typically stamp their hooves, and bite or rub at the backs of the legs. With time, some cases can develop severe crusting and scaling of the skin on the lower limbs, with skin thickening and general swelling, which can become infected and quite debilitating. As a result it is important to treat and control the condition effectively in the early stages to prevent it worsening.

This common skin condition is typically more of a problem during the winter when horses spend more time stabled and the condition often improves during the summer with increased turn out.

Feather mites in horses: Causes| | Signs | Diagnosis | Treatment

The mites responsible for chorioptic mange

According to Kieran O’Brien MRCVS, theses mites are of the species Chorioptes bovis, not Chorioptes equi as often described: “It is now thought that a true equine mite species does not exist, and consequently that cattle may infect horses and vice versa.”

The Chorioptes bovis mite is the guilty party. (Image credit: Marieke Brys)

The mite completes its full life cycle on the horse’s legs and feet within the horse’s feather. Eggs are deposited singly by female mites at the rate of one egg per day and are attached by a sticky substance to the host skin. Adult females usually live for four to six weeks or more, producing about 14–20 eggs during this time.

The eggs are often clustered, as multiple females deposit in common sites and return on successive days to deposit their eggs. The eggs hatch in four days and the cycle is completed in around three weeks.

Mr O’Brien warns that eggs and mites can survive for up to 69 days on bedding, floors and grooming equipment, and as a result, environmental “de-infestation” is an essential part of control.

It has been shown that some horses can harbour large numbers of mites without showing any external signs. A survey of 42 Friesian horses in the Netherlands¹ found mites on 26 of them, but only four had visible lesions.

It follows that in yards where there is at least one infested animal, other horses (including possibly those without feather) may well be carrying mites and may act as an ongoing source of infestation. Therefore treatment should also be applied to other horses living in close proximity.

Signs of feather mites in horses

Classic horse behaviour that signals the mites’ presence includes stamping of the hooves, either a single stamp or more commonly several stamps in quick succession. Also biting and rubbing their legs with the opposite hindleg or against fixed objects, for example against buckets or floor-level feeding troughs.

Irritation is usually low down around the pastern and fetlock area, although it will occasionally spread further up towards the back of the knees and hocks. While both front and hindlegs can be affected, the condition is more common in the hindlegs. Frequent stamping behaviour in a feathered breed is highly suggestive of mite infestation.

The mites feeds on superficial scales and debris on the skin surface, without burrowing into or puncturing the skin. The movement and feeding behaviour of the mites causes the lower legs to become itchy and irritated.

If the long hair is parted, scales and crusts will be seen in the pastern, fetlock and cannon regions. Trauma from biting and rubbing the legs will cause reddening and thickening of the skin and matting of the hair. Secondary bacterial infection may occur, with weeping and more significant crust formation. In long-standing cases some “corrugation” of the skin may occur at the back of the pastern.

In severe cases, horses may resent their legs (especially behind) being handled, and both clipping (if done) and any topical treatment may require the horse to be sedated first

Diagnosis

Diagnosis of feather mites in horses is usually based on the presence of the signs. The scabs can look similar to those produced by mud fever or pastern dermatitis, but excessive irritation indicates feather mites. The scabs may sometimes be mistaken for pastern leucocytoclastic vasculitis (PLV) or chronic progressive lymphoedema.

Skin scrapes can be taken, but can be hard to do properly on hairy legs, so mites can be lifted off on a piece of sticky tape to make a definite diagnosis; because these little parasites are too small (0.3-0.5mm long) to be seen with the naked eye, analysis under a microscope is required.

Mr O’Brien also suggests a clean toothbrush can be used to dislodge crusty material from the horse’s feather, which is then collected and examined.

Treatment of feather mites in horses

Some owners are reluctant to clip their horse’s feather, but doing so drastically improves the chances of treatment success.

There are currently no licensed medications for treating Chorioptic mites in equines, but most cases are treated through a combination of topical and systemic options, combined with active decontamination of the horse’s environment.

Mr O’Brien recommends shampooing the horse’s legs the afternoon before any topical treatment so the legs can dry overnight and any topical treatment applied the following morning. Topical treatments should be applied up to above the knees and hocks.

A mild antiseptic wash (such as a tea tree shampoo) should be used to help remove any serum or scabs and reduce the skin scurf. Your vet may need to sedate the horse for this procedure, as the legs are likely to be very sore.

Options for topical treatments include:

● selenium sulphide shampoo, such as Selsun (use neat) or Head & Shoulders Clinical Strength (diluted to 50% with water), applied and left in contact for 10 minutes before rinsing. Repeat on days five and 10. Ideally a “whole horse” treatment should be done once also.

● lime sulphur 5% diluted as instructed and applied without rinsing four times at weekly intervals.

● ivermectin, moxidectin or doramectin (doramectin can also be given by injection).

Licensed for the treatment of worms in horses, Mr O’Brien warns that the current emerging resistance to these medications indicates that we should avoid using them for mite treatment unless there are no alternative approaches.

He says: “Moxidectin, for example, is currently the only effective treatment for larval redworm diarrhoea – an often fatal condition – and this medication should therefore be used for mite treatment only in exceptional circumstances.”

● fipronil dog and cat flea treatment (such as Frontline Plus).

Mr O’Brien says: “Although it may be effective, the large dose required and the significant and persistent environmental effects of this compound (especially if it contaminates water sources), means that I discourage its use for sustainability reasons, and where there are other effective remedies.”

Decontaminating the horse’s environment

Because both the mites and their eggs can survive for up to 10 weeks off the horse, environmental decontamination is also important when treating feather mites in horses. Stables should be emptied of bedding and steam-cleaned, along with grooming equipment, clippers and rugs. Pay particular attention to disposing of any clipped hair and skin debris, as this will be heavily infested with mites.

Any animals in direct contact with those affected should also be treated to help avoid recontamination, but it is rarely feasible to treat every horse in a yard.

Sustained treatment of all individuals beyond the three-week mite life cycle, followed by quarantine measures and/or repeated preventative treatment prior to exposure of an untreated horse is often curative. Unfortunately, susceptible horses seem to easily become re-infected so ongoing management is often required.

References

1. Netherlands – Cremers – The Veterinary Quarterly 7:283 – 1985

An open study to evaluate topical treatment of equine chorioptic mange with shampooing and lime sulphur solution – Oct 2009

Comparative study of doramectin and fipronil in the treatment of equine chorioptic mange – September 2007

Pilot study to investigate the efficacy of a 1 per cent selenium sulphide shampoo in the treatment of equine chorioptic mange – June 1999

Oral ivermectin paste for the treatment of chorioptic mange in horses – Dec 1995

Vet Clinic – Feather foes, published in Horse & Hound magazine – 22 January 2026

For unlimited access to advice on how best to care for your horse, subscribe to the Horse & Hound website

Feather mites in horses (heel/chorioptic mange) is a challenging problem for owners

Carol Phillips — Tue, 27 Jan 2026 14:56:25 +0000

This article has been edited and approved by Karen Coumbe MRCVS, H&H’s veterinary advisor since 1991.

(Image credit: creditUnknown)

This common skin condition is typically more of a problem during the winter when horses spend more time stabled and the condition often improves during the summer with increased turn out.

Feather mites in horses: Causes| | Signs | Diagnosis | Treatment

The mites responsible for chorioptic mange

The Chorioptes bovis mite is the guilty party. (Image credit: Marieke Brys)

Mr O’Brien warns that eggs and mites can survive for up to 69 days on bedding, floors and grooming equipment, and as a result, environmental “de-infestation” is an essential part of control.

Signs of feather mites in horses

In severe cases, horses may resent their legs (especially behind) being handled, and both clipping (if done) and any topical treatment may require the horse to be sedated first

Diagnosis

Mr O’Brien also suggests a clean toothbrush can be used to dislodge crusty material from the horse’s feather, which is then collected and examined.

Treatment of feather mites in horses

Some owners are reluctant to clip their horse’s feather, but doing so drastically improves the chances of treatment success.

Options for topical treatments include:

● lime sulphur 5% diluted as instructed and applied without rinsing four times at weekly intervals.

● ivermectin, moxidectin or doramectin (doramectin can also be given by injection).

● fipronil dog and cat flea treatment (such as Frontline Plus).

Decontaminating the horse’s environment

Any animals in direct contact with those affected should also be treated to help avoid recontamination, but it is rarely feasible to treat every horse in a yard.

References

1. Netherlands – Cremers – The Veterinary Quarterly 7:283 – 1985

An open study to evaluate topical treatment of equine chorioptic mange with shampooing and lime sulphur solution – Oct 2009

Comparative study of doramectin and fipronil in the treatment of equine chorioptic mange – September 2007

Pilot study to investigate the efficacy of a 1 per cent selenium sulphide shampoo in the treatment of equine chorioptic mange – June 1999

Oral ivermectin paste for the treatment of chorioptic mange in horses – Dec 1995

Vet Clinic – Feather foes, published in Horse & Hound magazine – 22 January 2026

For unlimited access to advice on how best to care for your horse, subscribe to the Horse & Hound website

Horse & Hound’s definitive guide to equine vaccinations

Carol Phillips — Tue, 06 Jan 2026 09:29:39 +0000

This article has been edited and approved by Karen Coumbe MRCVS, H&H’s veterinary advisor since 1991.

(Image credit: creditUnknown)

If you aren’t sure about what vaccinations your horse needs, when they should be given and how often, then Horse & Hound’s definitive guide contains everything you need to know

There are a number of vaccinations for horses available to help protect your horse’s health. These include equine flu, tetanus, equine herpes virus (EHV) and equine rotavirus and strangles. Unfortunately a 2019 field trial of a vaccine to protect against grass sickness proved inconclusive.

Only healthy horses should be vaccinated. If your horse is showing any signs of being unwell, discuss this with your vet prior to any vaccine being given. It is recommended that a horse is given a couple of quiet days after being vaccinated, with only light work and turnout. A horse should not be worked hard or made to sweat as they may be feeling below par or a little sore at the site of the injection.

A small percentage of horses experience a reaction after being vaccinated. If your horse appears unwell then speak to your vet for advice. If your horse has previously had a reaction then discuss it with the vet prior to any future vaccinations being given.

All vaccination records should be kept up to date in the horse’s passport document.

What vaccinations does a horse need?

The most common vaccinations given to horses in the UK are for equine flu and tetanus. Equine flu vaccination is compulsory for horses competing in affiliated competitions and is recommended for all horses. Breeding stock should also be vaccinated for equine herpes virus.

How often does a horse need vaccinations?

Most governing bodies of equestrian sports require annual equine flu vaccinations after the initial course is completed. The FEI requires more frequent boosters. It is advised that owners of leisure horses also arrange yearly boosters.

Vaccines against tetanus are typically given to horses every other year.

The primary vaccination course for equine herpes virus in non-pregnant horses involves two vaccinations four to six weeks apart, followed by booster vaccines every six months. Pregnant mares are typically vaccinated at five, seven and nine months of gestation to reduce the risk of abortion associated with EHV.

Why you should vaccinate your horse?

“Equine vaccinations are important to prevent your horse from contracting nasty diseases, particularly contagious diseases such as equine flu,” explains Wolverhampton vet Sue Taylor.

“Horse owners often say that their horse doesn’t go anywhere and so doesn’t need to be vaccinated, but if your horse is on a stable yard alongside horses who do compete, there is a chance that those competition horses could bring back a virus.

“Herd immunity is a concept that owners should be aware of too. If there is a yard full of vaccinated horses, it provides a kind of ‘wall’ to flu and other viruses. It can’t pass on very successfully as vaccinated horses limit the amount of virus that is shed. Whereas if your horse is unvaccinated, they’ll catch it and snot virulent virus all over the place, making it more likely to be caught by other horses — even vaccinated horses can present with mild signs. The higher the vaccination percentage in the overall population, the less opportunities there are to infect horses.

“Also, owners of competition horses should be aware that an up-to-date vaccination record is a requirement of many sporting governing bodies for horses competing under their rules.”

Every horse should be vaccinated against equine flu. (Image credit: creditUnknown)

Equine flu (influenza) vaccination for horses

What is equine flu?

Influenza is a viral infection that affects the respiratory system resulting in a high fever, runny nose and coughing. Though rarely fatal, it can be a very debilitating disease that can take a considerable amount of time for horses to recover from. A major outbreak occurred in the UK during 2019 mainly affected unvaccinated animals, although some vaccinated horses also showed clinical signs.

Which horses need a flu vaccination?

Every horse should be vaccinated against equine flu. It is a requirement for competition horses to have up-to-date protection under the rules of most governing bodies.

Equine flu vaccination schedule

The first one is typically given around five months old, second one about four weeks later (21-60 days), then again around six months (120-180 days), followed by an annual booster. If you miss the window for these vaccinations or an annual booster, you will likely have to start the course again to comply with affiliated competition rules (check the rules of your governing body).

British Dressage, British Showjumping, British Eventing and British Riding Clubs require annual boosters. Horses competing under FEI rules must have been vaccinated within six months, plus up to 21 days, of a competition, but cannot have been vaccinated within seven days of arriving at a competition venue.

The flu vaccine is the only one that the FEI insists all horses taking part in international competitions have. From 1 January 2026, flu vaccinations must be recorded digitally in the FEI HorseApp, as well as in the horse’s passport. Vets must enter the vaccination details on the day it is administered. There is a transition period running until 30 June 2026 during which no sanctions will be issued, but from 1 July 2026 missing or incorrect digital records may result in fines.

The British Horseracing Authority’s windows between the first, second and third vaccines are 21-60 days, then 120-180 days, followed by six monthly boosters. In all cases, horses should not attend competitions within seven days of receiving a vaccine.

Other relevant info

Only healthy horses should be vaccinated for flu. If your horse has a temperature, cough or is unwell in any way, make your vet aware before he vaccinates your horse with flu, as the vaccine could make him more ill.

Tetanus vaccination for horses

What is tetanus?

Tetanus is caused by the production of endotoxins by the bacteria Clostridium tetani and is often fatal in horses. The spores of the bacteria are found in soil and enters the tissues via wounds. Deep puncture wounds are particularly dangerous as they provide an ideal site for infection.

Which horses need the tetanus vaccination?

Every horse is susceptible to tetanus due to the nature of the disease.

Tetanus vaccination schedule

A primary course of two vaccinations given four to six weeks apart, followed by a booster 12 months later. Subsequent vaccinations can be given at two yearly intervals. Foals will receive antibodies from their mother’s colostrum, but many are also given tetanus anti-toxin shortly after birth too.

Vaccination for tetanus is usually started at five months old and is often given as a combination vaccine with equine flu.

Other relevant info

You can get lumps or unwell horses occasionally after vaccination, but it is usually from a combined flu/tetanus vaccination rather than a sole tetanus injection.

Equine herpes virus (EHV) vaccination for horses

What is equine herpes virus?

There are five types of equine herpes virus, but EHV-1 and EHV-4 are the most clinically important and they are the only types that can be vaccinated against. EHV-1 and EHV-4 can cause a flu-like respiratory infection in horses, but may also cause abortion in pregnant mares and severe neurological disease. The effectiveness of the EHV vaccine against the neurological form of the disease is unclear.

Which horses need an EHV vaccine?

Any horse can have the herpes vaccine, but it is particularly important for breeding mares — many big studs will insist a mare is vaccinated before being allowed to foal there.

EHV vaccination schedule

The first vaccine can be given at five months old with the second vaccine at four to six weeks later, followed by a booster every six months. To provide effective immunity against abortion caused by EHV-1 and EHV-4 a course of three vaccinations should be given to a mare during her fifth, seventh and ninth months of pregnancy.

Other relevant info

There is a lot of virus shed in the aborted foetus’s fluid so surrounding mares can potentially catch the disease from breathing in the virus. The vaccine doesn’t always prevent the mare from aborting, but it can limit the amount of the virus that she passes when giving birth.

Equine rotavirus vaccination for horses

Pregnant mares are vaccinated against equine rotavirus to protect their foals from suffering diarrhoea or illness caused by the virus. Vaccines are given in the eighth, ninth, and 10th months of pregnancy in order that the antibodies can be transferred to the foal via the mare’s colostrum (first milk). Please contact your vet for more information.

New strangles vaccine

In 2004, a strangles vaccine called Equilis StrepE was launched, but unfortunately, three years later, it was withdrawn due to “quality control issues”.

Over a decade later, and a new protein-based strangles vaccine Strangvac has been developed by a group of scientists from the Animal Health Trust (AHT), the Swedish University of Agricultural Sciences, the Karolinska Institute and Intervacc AB, to prevent equines from contracting the highly contagious disease.

Trials were carried out on 16 horses, 13 of which were protected from strangles after being given the vaccine, and none showed signs of adverse reactions. The vaccine was made available to vets in the UK in 2022.

Strangles is caused by a bacteria called Streptococcus equi, which causes large pus-filled abscesses in a horse’s throat and neck. An estimated 600 outbreaks of strangles occur each year in the UK alone, so the development of the new vaccine will benefit horse health world-wide. Please contact your vet for more information.

Reactions to vaccines

“Some horses can have a reaction to their vaccination,” says Sue Taylor. “In some cases it is the injection itself that causes the reaction, not the vaccine. Vets shouldn’t swab the area of the vaccine injection because there is a risk that the antiseptic can deactivate the virus. If you have a very dirty horse, there is the risk that the needle will take bacteria in with it, causing an infection and abscess.

“I usually inject vaccines into the brisket (chest) which is often a cleaner part of the horse and if they do react, it drains well. A lot of people inject in the neck but if the horse reacts, it is a difficult area for the fluid to drain from, and the horse can find it difficult to put its neck down to eat and drink, and certainly can’t be ridden.

“If you have a very hairy horse, it might be advisable to clip a patch of hair with clippers or scissors to minimise the risk of dirt being taken in with the needle, or ensure the horse is clean in the area he is being injected.

“If they have a history of reactions, speak to your vet about placing the injection in his chest, and discuss the vaccine itself. In some cases, it is the carrier of the vaccine that causes a reaction, although this is much less likely now with modern vaccine technology. If you know that your horse is prone to reacting to a certain vaccine, tell your vet so that he can organise an alternative next time.”

Additional reporting by Stephanie Bateman

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(Image credit: Peter Nixon)

Equine flu: what horse owners need to know during the current outbreak in Britain

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Laminitis: how to spot the signs, plus treatments and ways to prevent it

Carol Phillips — Mon, 03 Nov 2025 15:12:50 +0000

This article has been edited and approved by Karen Coumbe MRCVS, H&H’s veterinary advisor since 1991.

(Image credit: creditUnknown)

Laminitis in horses occurs all year-round and is an emergency that needs prompt action whenever it is suspected, so find out how to recognise it and what to do if your horse is showing signs

What is laminitis in horses?

Laminitis in horses is an inflammatory condition of the laminae within the feet – the tissues that attach the pedal bone (the bone in the centre of each foot) to the hoof wall inside the hoof capsule. Although many people mistakenly think laminitis is only suffered by overweight ponies, horses of all types, age and size can develop laminitis for many reasons.

The condition occurs when the sensitive laminae within each foot become inflamed, but they are unable to swell since they are restricted by the solid external structure of the hoof. This leads to the horse feeling extreme pain and adopting the classic leaning back on the heels posture in an attempt to relieve the pressure from the front of the hoof. In the most severe cases the horses will lie down as their feet are too painful to bear weight.

An acute new episode or flare up of laminitis is a veterinary emergency and an equine vet should be called to assess any horse with suspected laminitis as a matter of urgency. Some horses and ponies have long standing chronic laminitis, which may not be an immediate emergency, but still needs expert care and attention. According to the RVC¹ more than 7% of equine deaths are linked to laminitis, with many cases being put down on welfare grounds.

Laminitis can develop very rapidly. It can result in the pedal bone sinking or rotating within the hoof and in extreme cases the pedal bone can drop so far that it penetrates through the sole of the hoof. If the pedal bone completely detaches from the hoof wall then the horse has ‘foundered’ and euthanasia may be the only option.

An X-ray showing the pedal bone has rotated towards the sole in a horse with laminitis. (Image credit: creditUnknown)

Laminitis: Signs | Diagnosis | Causes | Treatment | Prevention

Early signs of laminitis

Early signs of laminitis can be quite subtle and include the horse taking a shorter than normal stride and being reluctant to walk on hard or stony going, choosing grass or softer ground when possible. The horse may appear more lame on hard ground and turns, and may shift its weight between feet when standing still.

Acute signs of laminitis in horses

Lameness is typically seen in all four legs, although the forelegs may appear more badly affected. Signs of laminitis to look out for include:

An increased digital pulse at the back of the pastern/fetlock
The hooves may feel warm to the touch, although this alone is not a reliable indicator
Pain will be shown with use of hoof testers, especially around the point of frog on the foot
The horse stands leaning back onto its heels – the classic laminitic stance
The horse may lie down, and be unwilling to get to its feet

When do you see laminitis rings on the hoof?

Clear rings on the hoof wall can be a sign of a horse with chronic (i.e. long standing) laminitis. A horse that has suffered repeat bouts of the condition is likely to have misshapen feet with horizontal rings or lines on the hoof wall, which are wider at the heel than at the toe. The sole of the hoof may be flat or convex, with a wider than usual white line.

A horse that is overdue for shoeing with laminitis rings on the hoof wall that are likely to be linked to repeated bouts of chronic laminitis. (Image credit: Alamy Stock Photo)

How is laminitis diagnosed by a vet?

A vet should be consulted if laminitis is suspected and will usually diagnose the condition based on the clinical signs. X-ray images are useful to confirm whether the pedal bone has sunk or rotated, which will help as a guide to prognosis and inform the farrier fitting shoes. Blood tests can be very useful to help identify if any underlying endocrine disease is responsible.

What causes laminitis?

In general, ponies tend to be more susceptible than horses to laminitis, although the condition can affect horses of all breeds, sizes and ages. Risk factors associated with the disease include a flush of fresh grass at any time of year, grazing when the grass is under stress (such as after frost or severe overgrazing), and horses that are overweight.

Underlying conditions that can lead to laminitis include equine Cushing’s disease (also known as pituitary pars intermedia dysfunction or PPID) and equine metabolic syndrome (EMS). The hormone insulin appears to be significant in laminitis associated with endocrine disorders.

The RVC Equine department shared a timely warning on its facebook page in late October 2025 urging owners to be vigilant during autumn, saying: “The grass will continue to grow when the temperature is above 4°C, and on bright frosty mornings it will continue to make sugar but not use it up for growth, increasing the amount of sugar in each mouthful of grass.

“Research has shown that 90% of cases of laminitis are associated with an underlying endocrine (hormone) disease, with the two most common being equine metabolic syndrome (EMS) and pituitary pars intermedia dysfunction (PPID; also known as equine Cushing’s disease). In both of these diseases, it is high blood concentrations of the metabolic hormone insulin that seem to be responsible for causing the laminitis, and diet plays a big role in how much insulin there is in the blood at any given time, alongside the presence of EMS and PPID.

“It is important that animals with EMS or PPID are fed a diet low in sugar and starch and high in good-quality fibre to try and keep circulating insulin concentrations as low as possible.”

A 2021 study² conducted by Scotland’s Rural College in collaboration with the Waltham Petcare Science Institute found that steps taken to protect public health during the Covid-19 pandemic – including reduced exercise, turning horses away, and limiting yard visits – had the potential to compromise the welfare of overweight equines, increasing the risk of laminitis.

David Rendle, chair of the British Equine Veterinary Association’s health and medicines committee, said: “The study provides testimony that many horses spent additional time at grazing as a result of Covid health guidelines. Vets have been concerned throughout the pandemic that increased turnout during periods of good weather could tip laminitis-prone animals over the edge into clinical laminitis. The fundamental issue is the unacceptably high proportion of equines with obesity and associated metabolic disease.”

Research³ led by Garance Christen at the Swiss Institute of Equine Medicine, University of Bern, published in 2020, found that horses aged over 25 may suffer from chronic laminitis without displaying any outward signs or suffering from contributory health conditions. Almost half of the total sample of 51 clinically sound horses from different age groups (15-32 years) showed signs of rotation on X-ray, although none of them showed signs of acute lameness or PPID. Of these, horses aged over 25 were found to be three times more likely to have pedal bone rotation than horses in the younger age category.

The study’s authors said: “We think that radiographic changes are related to early or pre-clinical PPID in this cohort of horses because this remains the best explanation for the higher incidence of laminitis in the old age group.”

Other causes of laminitis

Laminitis can also be caused by a retained placenta after foaling, following on from another illness, limb concussion caused by excessive work on hard ground, or overload of a limb due to a severe injury of the opposing leg. In these instances, if the primary condition is effectively treated, the laminitis risk will subside.

In diseases associated with inflammation (such as certain types of colic, diarrhoea, retained placenta and severe pneumonia), the inflammation throughout the body triggers inflammation of the laminae, although why this happens remains unclear.

In mechanical overload laminitis, such as when a fracture or infected joint causes the other leg to bear all of the horse’s weight, it’s thought the excessive and continuous weight bearing may negatively affect the blood supply to the laminae.

Cases linked to concussion can occur during the summer in susceptible animals when a heatwave bakes the ground, with ponies in active service during the school holidays, as well as show horses and racing thoroughbreds, at a higher risk.

Laminitis treatments

A vet should be consulted regarding any suspected case of acute laminitis as soon as possible. They may prescribe non-steroidal anti-inflammatory drugs (NSAIDs) such as phenylbutazone or flunixin and potentially other painkillers to help manage the horse’s discomfort.

Foot support and complete rest to limit movement of the pedal bone is important and will help to reduce the extreme levels of discomfort. The horse should be placed on box rest on a deep bed of shavings or other similar bedding right up to the stable door. Special supports can be attached to the horse’s hooves by your vet or farrier to give additional support.

Acepromazine (ACP) has been frequently used to increase the blood supply to the feet, but it’s beneficial effect may be more due to its sedative properties, which will encourage the horse to stand still or lie down.

In cases of laminitis associated with inflammation, the use of ice to cool the feet may be beneficial, especially in the very early stages of the disease. Research comparing seven different ways of cooling the hoof⁴ found immersion of the foot and at least the pastern region of the leg in ice and water achieved the lowest hoof wall surface temperature for a sustained period, along with use of a prototype perfused cuff device with a dry interface. In summary, when apply cold therapy, the cooling should cover the whole hoof as well as the lower part of the leg for the greatest effect.

If the laminitis is the result of an underlying condition, such as an endocrine disorder, that should be treated accordingly. Discuss this with your vet, depending on the results of blood tests. If a horse or pony has insulin regulation problems caused by EMS or PPID, or both, he will certainly be at increased risk of developing laminitis and will require careful management. By diagnosing these underlying problems the vet can guide the owner more clearly and manage the case more effectively.

A new treatment for laminitis

Ertugliflozin, an SGL2 inhibitor used to help lower blood glucose levels in humans, has been found to successfully lower insulin levels in horses, and is being successfully used in the treatment of laminitis and equine metabolic syndrome (EMS).

Veterinary expert David Rendle, who has been involved in the early research⁵, said the drug can bring insulin levels down “remarkably quickly”, adding: “We have found in cases of laminitis the horse’s level of comfort increases very quickly. Everything is pointing toward SGL2s being an effective way of reducing the suffering associated with laminitis.”

Although the drug does not have marketing authorisation for use in horses, but it can be prescribed by a vet in the UK.

Research published in April 2024⁶ examining horse owners’ experiences and observations following the use of this treatment found 85.3% of 342 owners reported their horses had an improved quality of life after commencing treatment, while 9.4% reported no change and 5.3% reported a worsening of clinical signs.

Of the owners who had thought they might need to end the lives of their horses prior to treatment, 80.5% reported their horse’s level of pain to be either mild or absent after 30 days of treatment and 94.8% reported their horse’s quality of life to be improved. Side effects were seen by 114 owners (33.3%), particularly excessive urination (20.5%), excessive drinking (11.1%), excessive weight loss (9.9%) and dullness (7.6%).

Overall the study found that treatment resulted in excellent rates of owner satisfaction and owner-reported improved quality of life for the horse; although, some adverse effects were observed.

Feed for horses with laminitis

Diet is very important during bouts of laminitis. Clean fresh water should always be available while the horse should be fed poor quality hay, rather than grass. The hay should be soaked for at least an hour to reduce soluble carbohydrate levels. Fibre-rich feeds, such as unmollassed sugar beet and low-sugar chaffs or hay replacers, can also form part of the diet.

Horses that are overweight should not be starved in an attempt to shift excessive condition as doing so risks triggering hyperlipaemia, a disorder of fat metabolism.

All horses need to receive a balanced diet of vitamins and minerals, so discuss the best way to supply this with your vet. Once the acute stage of the condition is over, hoof supplements can be used to promote healthy hoof growth, while other supplements are formulated to help support healthy horses on restricted grazing. There are also feeds marked as suitable for horses prone to laminitis by The Laminitis Trust.

How to prevent laminitis in horses?

While it is not only overweight horses that get laminitis, the weight of all equines should be carefully managed to reduce the associated risk. Horses of all types need to go into the spring in lean condition (where you can easily feel and just start to see their ribs) to avoid the risk of obesity as the levels of nutrition in grazing improve.

Winter is a great opportunity to achieve weight loss in overweight equines by keeping them unrugged and not increasing hard feed, unless the horse drops clearly below a healthy bodyweight. Grazing muzzles can be used all year round to help control weight gain.

All horses hooves should be attended to by a qualified farrier or podiatrist every four to six weeks, whether they are shod or not, to maintain correct hoof balance and health. Appropriate shoeing can make a huge difference to the chronic laminitic by supporting the structures in the foot properly. There are many options of useful shoes designed to help laminitis cases including mouldable thermoplastic shoes and clogs amongst others.

The farrier who sees the case every few weeks is also in an excellent position to guide the horse owner, who sees their animal daily and therefore may not notice changes, especially in weight.

It is recommended that all riders avoid excessive trotting/cantering on hard ground, including roads, to reduce the concussion on the horse’s limbs and feet.

In broodmares after foaling, check that the whole placenta has been expelled. If you are unsure if this is the case, contact your vet urgently.

If your horse is recovering from a severe injury to one leg, discuss with your vet the best way to provide additional support to the opposing limb.

Above all be aware that we now know that there is much more to laminitis than simply avoiding lush grass. Underlying metabolic problems, proper regular attention to the feet and good general health care are all important.

Laminitis FAQs

What is the worst time of year for laminitis?

While laminitis can occur at any time of year, it is often seen in spring when the grass grows at a fast rate. This is typically the case in overweight equines, who are suffering with associated metabolic disease.

Should you walk a horse with laminitis?

No, a horse with laminitis should not be walked. Any horse with laminitis should be kept on box rest with a deep soft bed, such as shavings, to limit the risk of movement of the pedal bone while the inflammation of the laminae is ongoing.

How long on box rest for laminitis?

Every case of laminitis is different, but a horse is likely to need to be on box rest for at least a month after the initial signs of pain pass, even for a mild case of laminitis. More serious cases are likely to have to remain on box rest for a number of months while treatment is ongoing.

References and further reading:

Atypical myopathy: what you need to know right now to keep your horses safe

Carol Phillips — Wed, 22 Oct 2025 08:22:50 +0000

This article has been edited and approved by Karen Coumbe MRCVS, H&H’s veterinary advisor since 1991.

(Image credit: creditUnknown)

Atypical myopathy in horses (also known as seasonal pasture myopathy, sycamore myopathy or sycamore poisoning) is an often fatal illness, usually found in grazing equines — mostly in the autumn and spring.

With the first of the UK autumn storms of 2025 having passed, H&H has been contacted by owners who have lost horses to atypical myopathy after grazing around sycamore trees. This year is a mast year for many types of trees (including oak), which means there is a very large number of seeds being produced, which increases the risk. Periods of high winds can result in large dumps and carry the shedding seeds and leaves over long distances, so the risk isn’t limited to sycamore trees in or on the fence lines of paddocks.

The British Equine Veterinary Association (BEVA) has previously reminded owners of the dangers. “With leaves still on trees now is the time to identify sycamores in the vicinity of your horse’s fields and predict the future risk,” said Lucy Grieve, veterinary projects officer at BEVA. “Once the leaves start to turn and then drop it will be much more difficult to spot sycamores.”

This serious threat to horses’ health weakens the muscles of the horse’s body, including the heart, and can present with sudden stiffness, muscle tremors, collapse and colic-like signs, accompanied by a low temperature. Often dark urine is seen because the damaged muscle cells release the pigment myoglobin, which can damage the kidneys.

Atypical myopathy has a fatality rate of around 70% so should always be considered a veterinary emergency if it is suspected.

Atypical myopathy is not infectious and can affect horses of all ages and types, although young horses may be more vulnerable. Some horses appear to be more susceptible than others, which may be due to genetic differences.

What causes atypical myopathy in horses?

Studies have established that atypical myopathy is caused by ingestion of the hypoglycin A toxin from the seeds, seedlings and possibly flowers of certain trees of the genus Acer. The most common of this type in the UK is the sycamore tree, but different trees contain variable amounts of the toxin. It is important to note that the toxin is not present in every seed, seedling or tree.

The Royal Veterinary College provides a hypoglcyin A test that can be used on both plant samples and equine serum to identify the level of the toxin. This can vary within an individual tree from year to year, although a 2025 study found that trees in the same area typically have similar concentrations of hypoglycin A in their seeds. The study also found that toxicity could occur from water sources containing sycamore seeds and leaves.

Hypoglycin A prevents energy being produced within the muscle cells.

Much research has been done by the University of Liege and involved horses from Belgium, Germany and the Netherlands. High concentrations of hypoglycin A were found in all the sick horses. Botanists visited the pastures that had been grazed and the sycamore was found to be nearby in every case.

In the United States research has linked seasonal pasture myopathy (the US equivalent) to toxins from the box elder tree. Both trees produce seeds containing the agent hypoglycin A.

Sycamore seeds have a downward V shape with “wings” to help them travel on the wind, while the leaves of the trees have five points. (Image credit: Stephen Iles / Alamy Stock Photo)

The “helicopter” wing-shaped seeds are thought to be the primary source of the toxin, but sycamore seedlings have also been found to contain the toxin, being a particular concern in the spring. It is recommended that seedlings are mowed and the cuttings collected and removed from the pasture afterwards as the toxic hypoglcyin A remains in the plant material after it has been cut.

Sycamore seedlings are also a cause for concern and should be removed from pastures where horses graze. (Image credit: Alamy Stock Photo)

When are horses most at risk?

Outbreaks of the fatal condition tend to be seasonal, with cases typically occurring in the autumn and spring. Victims are usually kept in sparse pastures, where seeds or seedlings are on the ground and are eaten when there is not much other grazing available. Windy autumn weather is particularly risky as it can deposit large numbers of sycamore seeds on to grazing land, which are then eaten.

What are the signs of atypical myopathy in horses?

The onset of the disease can be extremely rapid, with some horses being found collapsed or dead in their fields. Signs include:

Stiffness
Weakness
Reluctance to move
Lethargy
Muscle tremors
Muscle pain
Sweating
Difficulty breathing
Shivering
Dark red or brown urine
Fast, irregular heart beat
Colic signs
Unable to stand
Sudden collapse and death

How is atypical myopathy diagnosed?

Your vets will be able to make a likely diagnosis based on the clinical signs as well as the horse’s environment, along with lab tests to confirm the levels of toxicity.

What treatment is available?

Horses diagnosed early will need treatment with intravenous fluids, pain relief and intensive care at an equine hospital, but once the signs are present it is already serious. Affected animals often deteriorate for the first 24 to 48 hours so should be moved to an equine hospital as soon as possible after the diagnosis is made as the period the horse is able to remain standing while in transit is going to be limited.

There is a compromise in that the horses do not want to be moved far, however effective intensive care is not really possible in the field, where they may be ingesting more toxin.

Supportive therapy including vitamins, minerals and antioxidants may be helpful.

A 2018 study showed that activated charcoal may bind the toxin, so your vet may consider stomach tubing with this following removal of any cases from pasture.

Atypical myopathy in horses: what is the prognosis?

With some 70% of cases proving fatal, the prognosis for horses with atypical myopathy is cautious at best. However, if a horse can survive the first few days of treatment, they can go on to make a full recovery over a period of some months with no long-term effects of the disease.

How can owners reduce the risk?

Identify trees both around grazed fields as well as those in close proximity
Fence off areas where sycamore seeds and/or leaves have fallen
Regularly inspect fields to ensure seeds have not blown in from nearby sycamore trees
Remove any seeds and leaves that have dropped into water troughs
Mow areas where seedlings are growing and collect the cuttings
Supply extra forage (hay or haylage), especially where pasture is poor
Reduce stock density, so there is enough good grazing for every horse
Turn out horses for short periods (ideally less than 6hrs.)
Pick up and remove sycamore seeds, if possible
Test for the presence of hypoglcyin A in your pastures
Monitor horses carefully and if concerned, contact your vet immediately

If a case occurs and your horse is in the same field, ask your vet for advice and consider moving your horse.

Further reading:

Assessment of tree-associated atypical myopathy risk factors in Acer pseudoplatanus (sycamore) seeds and leaves – January 2025

Royal Veterinary College’s atypical myopathy fact sheet for horse owners [PDF] – 2022

Answers to the Frequently Asked Questions Regarding Horse Feeding and Management Practices to Reduce the Risk of Atypical Myopathy – February 2020

Equine atypical myopathy in the UK: Epidemiological characteristics of cases reported from 2011 to 2015 and factors associated with survival – April 2017

The Story of Equine Atypical Myopathy: A Review from the Beginning to a Possible End – November 2012

Equine herpes virus – all you need to know right now

Carol Phillips — Tue, 19 Nov 2024 14:14:21 +0000

This article has been edited and approved by Karen Coumbe MRCVS, H&H’s veterinary advisor since 1991.

(Image credit: creditUnknown)

The equine herpes virus is always present in the British horse population, but the British Equestrian Federation is advising owners to be “extra vigilant” while they monitor a reported outbreak of the neurological form of the virus in France

The equine herpes virus (EHV) is widespread among the horse population in many countries, including Britain. It is thought most horses have been exposed to the disease when young, usually by the age of two and then become latent carriers of the virus. A horse can therefore be infected for life, and can intermittently discharge the virus from the nose and infect susceptible horses. The virus lays dormant in these horses before becoming active again at times of stress. It is important to understand that horses do not always show clinical signs while they are shedding the virus.

EHV has nine strains, with five (EHV-1 to EHV-5) affecting horses.

The two most common strains are EHV-1, which can cause respiratory problems, abortion in pregnant mares and, in rare cases (including an outbreak in southern Britain in January 2020 and a major outbreak linked to a showground in Valencia, Spain that began in February 2021 and spread widely around Europe), neurological problems leading to paralysis and in some cases death; and EHV-4, which most commonly causes mild respiratory problems and very occasionally a single case of abortion in a pregnant mare.

EHV is not a notifiable disease by law in the UK, although the Horseracing Betting Levy Board’s code of practice for the disease calls for thoroughbred breeders to notify the Thoroughbred Breeders’ Association if EHV abortion or neurological diseases occur. Other breeders should inform their relevant breed association. Previously the Animal Health Trust also kept track of cases, but they can now be followed through the International Collating Centre (ICC).

There is a vaccine available for EHV, but effective biosecurity is equally important, alongside quarantine during an outbreak. Regular vaccination can lead to a reduction in infectious virus circulating in the population and it is likely to have helped, along with preventative management measures and biosecurity, in reducing the number of outbreaks of disease reported. There is evidence of reduced respiratory disease and abortion in vaccinated animals, however the efficacy of vaccination to prevent the neurological form of the disease is unclear.

It is not recommended to use the vaccine on any horses that may have recently been exposed to the infection while an outbreak is ongoing. That said, vaccination may be advisable for the horses, outside the immediate geographical location of the outbreak, to reduce the long term viral shedding and improve herd immunity. There are currently no official requirements for vaccination against equine herpes virus in the United Kingdom, but it is required for thoroughbreds racing in France.

Types of EHV

EHV-1 can cause respiratory disease in young horses, abortion in pregnant mares and paralysis in horses of all ages and types. The neurological form that causes paralysis is called EHV-1 myeloencephalopathy (EHM).

EHV-2 rarely leads to clinic signs, but it can suppress immunity and make the horse more prone to other infections as well as causing respiratory disease in some cases.

EHV-3 is a venereal disease that causes lesions on the penis of stallions and the vulva of mares.

EHV-4 usually causes low-level respiratory problems, but can occasionally cause abortion. It is also known as equine rhinopneumonitis virus.

EHV-5 is associated with pneumonia and lung scarring (equine multinodular pulmonary fibrosis) in adult horses

EHV-6 to EHV-9 cause infections in wild equids, including asses and zebra.

Is it serious?

While most cases of EHV result in a relatively mild respiratory disease, it can cause either a single or group of pregnant mares to miscarry their unborn foals without warning, or a horse to show mild neurological abnormalities when walking and within hours be unable to stand.

The risks should not be under-estimated and a vet should be contacted for any horse showing signs. Data from recent outbreaks suggest the virus may be becoming more virulent, i.e. more likely to spread. This is another reason why effective biosecurity is so important.

Following the major outbreak in Europe in spring 2021, the FEI put in place new horse health requirements to help protect horses competing at international events.

What are the signs of equine herpes virus?

Most often seen in groups of young horses (weaned foals and yearlings), the signs of the respiratory form of the disease may include:

Raised temperature
Coughing
Watery nasal discharge that can become thick and infected
Lack of interest in food
Swollen glands around the throat
Conjunctivitis

Signs of the neurological disease may include:

Lethargy
Hind limb weakness and a lack of coordination
Head tilt
Inability to lift the tail
Dribbling urine/difficulty in urinating
Leaning against a fence or wall
Inability to stand
Neurological signs may be preceded by fever and respiratory signs

In abortion cases, the mare will unexpectedly lose her unborn foal, or a foal carried to term may be born weak, with breathing problems and die within the first few days.

Respiratory disease caused by EHV is most often seen in weaned foals and yearlings, typically in autumn and winter. However, older horses can also pick up the virus without showing obvious signs and then transmit it to others. The ability to shed the virus without showing signs is why EHV can spread widely leading to abortion in pregnant mares and cases of EHV neurological disease in horses of all types and ages.

How is it spread?

A horse becomes infected with EHV by inhaling the virus that has been expelled into the air by an infected horse coughing or sneezing, or it can be transmitted via infection in the local environment, or directly from horse to horse.

Unlike equine flu, EHV does not travel long distances in the air (only up to about 50 metres), but it is thought to be increasingly infectious and can spread quickly within groups of horses that are living together either in paddocks, open barns or America barn-style stable yards, or when they come into contact with other horses at shows or training events.

The incubation period may be as short as 24 hours, but more typically is approximately four to six days, and horses are most infectious in the early stages of infection (when their temperature is raised). This is why regular twice daily monitoring of temperatures is a wise protective precaution.

When mares abort due to the EHV infection, the fetus, fetal membranes and fluids can release large quantities of infectious virus into the local environment, which can then be inhaled or spread indirectly by those caring for the mare and the equipment they use. This is a particular concern when horses are stabled with shared air space, which allows the virus to spread, such as within a barn, without the wind being able to dissipate the infection as it would in an outdoor paddock. The virus can survive in the local environment for up to a month after being shed by a horse.

Diagnosis of equine herpes virus

Your vet will base their diagnosis on clinical history and signs, followed by tests to isolate the virus on nasal swabs taken as early as possible after infection is suspected.

In addition blood samples will be taken to measure the levels of antibodies in the blood when the horse is first examined by the vet and then again two to three weeks later. An increase in the levels of antibodies seen in the blood will confirm recent exposure to the virus.

Treatment of equine herpes virus

There is no specific treatment for EHV currently available, so careful nursing is key to helping horses recover. Because EHV is a virus, antibiotics are not effective against it, but your vet may prescribe them where a secondary infection is present. Non-steroidal anti-inflammatory medication can help reduce high temperatures and give pain relief where necessary. Intravenous fluids may be required in some cases. Occasionally anti-viral medications are prescribed, although these are not licensed for use in horses.

Horses showing signs of a respiratory infection should receive complete rest in a dust-free environment.

Horses showing neurological signs should be cared for in an appropriate location, such as a well-bedded stable, barn or paddock with feed and water within easy reach. If a horse becomes unable to stand and remains recumbent, nursing care becomes challenging and regrettably euthanasia may be recommended on welfare grounds. There are a few reports of some recumbent horses that have recovered with intensive care, careful nursing and support, for instance, with purpose-designed slings.

Mares that have aborted due to EHV usually appear well in themselves and do not require any special nursing, but they should be isolated for 28 days to reduce the chance to spreading the infection further and kept separate from other pregnant mares for eight weeks.

What to do during an equine herpes virus outbreak

If a case of EHV is confirmed on your yard, then all horse movement on and off the premise should cease. It is recommended that movement restrictions are kept in place for at least 28 days after the last case and that the local equestrian community should be informed.

Horses that are confirmed with EHV should be isolated with strict barrier nursing and biosecurity measures put in place to reduce the likelihood of the virus spreading. Ideally separate staff should attend to the infected horse(s) using suitable protective clothing and biosecurity protocols to reduce the risk of spread of infection.

The use of virucidal disinfectants and heat can destroy the virus so stables, equipment and transport should be cleaned, steam cleaned and then disinfected with an approved disinfectant. Bedding should be removed and destroyed. Where possible virucidal disinfectant should be allowed to dry naturally on suitable surfaces to maximise the chance of destroying the virus.

If there is an outbreak of EHV in your local area, it may be wise to stop hacking out or going to external training, shows or hunting to minimise the risk of coming in contact with the virus. This will help to contain the outbreak and prevent it spreading to other yards.

Can you vaccinate against equine herpes?

There is an equine herpes vaccine available with evidence of reduced respiratory disease and abortion in vaccinated animals, however the efficacy of vaccination to prevent the neurological form of the disease is unclear.

In non-pregnant horses, the primary vaccination course involves two vaccinations four to six weeks apart, followed by booster vaccines every six months. Pregnant mares are typically vaccinated at five, seven and nine months of gestation to reduce the risk of abortion associated with EHV.

It is not recommended to vaccinate any horse that may have recently been exposed to the virus. Horses that have no risk of having been exposed to the virus can receive the vaccination while an outbreak is ongoing, provided they are not going to be exposed in the near future, e.g. they are going to remain in a closed yard and are not going to be travelling. It is not recommended to vaccinate any horses in the vicinity of any suspected outbreak.

Vaccination is particularly useful for horses less than five years of age, those in contact with pregnant mares and horse kept where there are frequent equine movements on and off the premises.

How to prevent an equine herpes virus outbreak

Good biosecurity and hygiene practices are key. Even if your horse is vaccinated, you should still be strict in observing effective biosecurity measures.

Biosecurity recommendations include:

When away from your own yard, do not allow your horse to touch other horses, share drinking water or graze
Avoid touching other people’s horses or sharing any equipment
Practice hand washing in between handling horses
Keep separate feed buckets, brushes, towels, and tack/equipment for each horse
Know your horse’s normal temperature and take it twice a day, especially after your horse has been away to a show or external training session
Have a plan for isolating new arrivals or potentially infected horses
Early identification and reporting of ill horses is vital in order to trace possible points of exposure and to aid in the prevention of further spread of the disease.

There is a view that the management in the early stages following identification of a potentially infectious horse frequently determines the extent and scope of transmission and potential outbreak.

Always ensure you are ready for rapid implementation of an isolation plan at a competition grounds and/or at your home yard. Although not all yards have such a facility, it makes sense to isolate horses at first signs of illness and contact your vet immediately for advice.

When any new horse comes on to your yard, it should be isolated for three to four weeks to avoid bringing a new infection into an established group of horses. You should also consider what precautions to apply when a horse is returning to the yard from a show, training or veterinary treatment.

Due to being at particular risk from EHV, it is recommended that pregnant broodmares be kept separate from horses that are attending competitions or external training sessions.

If you have any concerns or questions, always consult your own vet.

Further reading