Biosecurity

“Not again” is the thought going through my head this weekend as the equine world reacts to the news of an EHV outbreak at a competition venue. Last year, it was the flu outbreak, this year EHV. The reaction has been strange this time round. Last year I felt there was a very panicked, almost hysterical air. This year there has been a more prompt, and complete, response from training and competition venues in the area or with links to the infected venue, but the general equine population seems to be more confused – some are taking extreme precautions, others are continuing as normal.

Perhaps it’s because Equine Herpes Virus is less well known than Equine Flu, or perhaps it is the fact the flu epidemic was in random places, so very difficult to contain or predict it’s movement – an attack from all sides, so to speak. Perhaps it’s because everyone knows the drill for lockdowns. Or on the flip side, people are fed up of stringent checks.

EHV is always mentioned in stable management training, within the subjects of vaccinations and breeding, but I’ve only a sketchy knowledge of this often fatal virus, so I’ve found a much better article about it, which you can read here.

I’m not going to start telling everyone what you should be doing, in terms of hacking, travelling or yard lockdowns. After all, that depends on your location, proximity to the outbreak, disciplines, size of yard, facilities, and risk category of horse.

But I think it’s worth discussing biosecurity measures, which in all honesty, often become slack because they are quite laborious and time consuming.

Firstly, there is the basic yard hygiene of ensuring that each horse has their own grooming kit and feed and water buckets, and avoid sharing rugs, tack and protective equipment as much as possible. Wash out buckets daily, clean grooming kits regularly, wash saddle cloths regularly and don’t share them between horses. The same goes for rugs. Daily procedures like this take very little time and will stop any diseases passing between horses from indirect contact. In particular, not sharing grooming brushes or rugs or numnahs reduces the spread of skin infections, such as ringworm.

Of course horses on yards will have nose to nose contact with their field and stable companions and neighbours, but this can be minimised by putting inner electric fences round fields so that horses can’t reach each other (unless they are half giraffe!) and by not having grills between stables you can reduce direct contact between horses, which will reduce the spread of illnesses.

Washing hands when you leave the yard is a basic hygeine procedure from a human point of view, but it will also stop the indirect spread of disease when visiting other horses. I keep hand sanitiser in my car for this very purpose.

What other basic biosecurity measures can you take without disturbing your daily equine routine? When we’re all out at competitions and clinics as normal, do you let your horse sniff unknown horses? Personally I don’t. I keep a slight distance and avoid letting Phoenix touch noses with any horse from a different yard, even if I know their owner. Of course, it’s not going to stop the airborne spread of illnesses, but stopping direct contact will reduce the risk. And of course, using your own equipment and providing your own water will reduce the risk further.

Finally, you should take your horse’s temperature on a regular basis to establish what is normal for your horse so that you can quickly identify when they develop a fever. I remember when we had strangles on the yard when I was young one of the riding school ponies had strangles but his temperature was the normal 100F. But his baseline temperature was 98F, which meant he could easily be overlooked as healthy when he was actually very ill.

Big biosecurity steps to take is disinfection, which should happen all the time, but often people get complacent. For example, when a horse leaves the yard their stable should be disinfected before another horse moves in, in case the previous horse was a carrier of a disease and passes it onto the new occupant. When a new horse arrives on a yard they should be isolated for two weeks. Proper and correct isolation means a separate stable block, handlers washing and changing clothes between caring for the new horse and the rest of the yard, separate mucking out equipment, separate brushes, rugs etc. You should even burn the muck and bedding, keeping it separate from the main muck heap.

If you hire a horse box it should be disinfected before and after use, so check with the company you are using that this is their procedure.

Now that there’s a higher risk of disease, it’s time to step up the biosecurity measures you take on a daily basis. Change clothes and disinfect footwear when leaving the yard, reduce the number of different yards you visit – a farrier may want to reschedule his clients so he minimises the number of yards he visits in a day, and if you’re going to see a friend and their new horse it might be worth postponing a week or two. I will be having numerous changes of clothes each day for each yard and having a portable boot wash so I can dip my boots in disinfectant when I leave a yard.

Like with anything, it’s important not to panic, but to be sensible; don’t go anywhere unnecessarily, or to heavy traffic areas, and maintain daily hygeine procedures.

I found this useful website about equine biosecurity from the British Equine Federation.

Equine Herpes Virus

We all know how contagious strangles is, and there’s a growing movement, quite rightly, about reporting cases in the local community to try to reduce the spread of the disease. Hopefully the stigma associated with strangles is dissipating, but of course there is a new disease doing the rounds to get hot under the collar about. 

Equine Herpes Virus is not a new disease, but it is becoming more prevalent. There are several strains of EHV that affect domestic horses – EHV-1,-2,-3,-4 and -5. 

EHV-1 causes respiratory disease in young horses, abortion in pregnant mares, death of newborn foals, and paralysis in horses of all ages and types. 

EHV-2 also causes respiratory disease, but is linked to conjunctivitis and swollen submaxillary and parotid lymph nodes.

EHV-3 is a venereal disease that causes pox-like lesions on the penis of stallions and the vulva of mares. It is quite rare, rarely causes death or need treatment.

EHV-4 usually only causes low-grade respiratory disease but also occasionally causes abortion.

EHV-5 is a virus that is currently associated with unusual sporadic cases of debilitating lung scarring in adult horses.

EHV-2 and EHV-5 are found in most horses, but rarely cause disease. It’s been suggested that a horse carrying one of these strains of EHV predisposes them to other illnesses.

However, EHV-1 and EHV-4, which are both DNA viruses, cause more serious problems.

The neurological symptoms of EHV-1 are varied but include hind limb weakness and loss of coordination, which can progress to recumbency and paralysis. EHV-1 is also the cause of a recently identified syndrome, peracute vasculitis, which is fatal to adult horses.

EHV-4 rarely causes abortion or neurological disease, but the associated respiratory disease can be severe, although it is not fatal.

Unfortunately, once horses have been infected with a strain of EHV they carry the virus silently, a bit like humans with cold sores, reactivating at intervals throughout their life. This means that EHV-1 and EHV-4 are extremely widespread, and although most horses will have the virus many of them will not show signs of illness most of the time. However, periodically there are outbreaks of disease, like there is in the UK at the moment. This is because if the virus reactivates it goes on to multiply and possibly cause clinical illness in the horse. At this point the virus is spread through aerosolised droplets, which can infect other horses through inhalation or ingestion. Reactivation of latent virus can occur when the horse is stressed -for example during illness, transportation or weaning.

EHV abortion can occur from two weeks to several months following infection with the virus, reflecting either recent infection or re-activation in a carrier horse. Abortion usually occurs in late pregnancy (from eight months onwards) but can happen as early as four months. Respiratory disease caused by EHV is most common in weaned foals and yearlings, often in autumn and winter. However, older horses can succumb and are more likely than younger ones to transmit the virus without showing clinical signs of infection. It is the continual cycling of EHV respiratory disease in young horses and the periodic reactivation of latent EHV in older horses that maintains the risk of EHV abortion in pregnant mares and EHV neurological disease in horses of all types and ages.

There are no vaccines currently available that provide complete protection against equine herpesvirus. The vaccines that are available give some protection against respiratory disease and can help to reduce the spread of infective virus, and often studs require mares to be vaccinated against EHV. However, vaccination should be viewed as assistance to disease control alongside good equine management. 

To reduce the incidence of EHV outbreaks, sick animals should be quarantined from healthy horses and strict hygiene precautions established. Yards with ill horses should go onto lockdown and reduce the spread of the disease to other yards. Weanlings and young horses are more at risk from the reactivating virus should be isolated, especially as carried horses often don’t have any symptoms.

The first symptom of EHV is a rise in temperature, and then respiratory symptoms of nasal discharge and coughing appear. If it is the neurological strain, then signs of stiffness will appear. However, diagnosis of EHV can only be confirmed in the laboratory. 


Within each type of EHV there are many different strains circulating in the horse population, in much the same way there are numerous strains of the flu virus, and the reason no one vaccine is all encompassing. These strains can differ from each other by just a few amino acids, but the mutations can make the strain behave quite differently from other strains. This also makes it harder to diagnose EHV and this yards can be slow to put bio security measures into place, thus allowing the virus to spread.

In my research about EHV, I found this useful article about how to prevent the spread of the disease – Have a read here.