Biosecurity has become a buzzword in the equine world.
The spread of disease has always been a threat, but now people are recognising and discussing the problems when previously infection control was a taboo subject due to the stigma associated with “contamination”.
Infectious diseases are, in fact, an ever-present health risk for every horse and a potential danger to the whole equine industry. Control in the form of well-considered biosecurity is important, although there can be a fine line between paranoia and responsibility.
Biosecurity needs to be a sensible, informed risk assessment. There are many more problems in large yards with transient horse populations compared to smaller groups of horses with minimal horse movements off-site, although infections can appear anywhere.
10 tips for infection control
1. Monitor your horses for signs of infectious disease and seek veterinary advice if you suspect a problem.
2. Establish a quarantine procedure for any new arrivals. Isolation for three weeks is generally adequate but check with your vet whether tests — such as swabbing or blood tests for strangles — are worthwhile.
3. Maintain high levels of hygiene at all times. Clean and disinfect yard areas and equipment regularly.
4. Avoid sharing equipment, including tack, feed and water buckets and brushes.
5. Create adequate ventilation, especially in barns, to lessen respiratory irritation.
6. Reduce areas of standing water at the yard to control insects and vermin.
7. Segregate age groups where possible. Keeping pregnant mares separate is advisable in certain situations such as at studs. Ideally, you should segregate travelling horses on their return to the home yard to guard against infection.
8. At shows, limit horse-to-horse and horse-to-human contact.
9. Know your horse’s normal temperature and check it if you are concerned about his health.
10. Maintain an adequate vaccination programme — ask your vet for more details.
What are the global risks of infectious diseases?
One would hope that infectious diseases would have decreased as veterinary medicine has advanced, but this is not the case.
The last decade has seen the epidemic spread of West Nile virus in North America; a major equine influenza epidemic and alarming reports of the Hendra virus — which can cause both horse and human deaths — in Australia; plus outbreaks of contagious equine metritis reported in several countries.
In addition, there are increasing concerns regarding paralytic herpes virus (EHV-1) and multi-drug-resistant bacterial pathogens such as MRSA — an increasing issue across the globe. Then there are the equally distressing outbreaks of more common problems, ranging from strangles to ringworm, which disrupt our equine populations on a regular basis.
Some infections now appear to be more prevalent. Perhaps the causative agent is more potent, or maybe it is because there are more horses travelling to spread disease. It could just be the fact that outbreaks are more widely reported.
Either way, there are significant risks when large numbers of horses gather for specific events.
The potential for serious and widespread repercussions when these horses move on elsewhere was seen at a cutting horse event in the US state of Utah during 2011.
It is thought that exposure to a single horse shedding EHV-1 at this event resulted in more than 165 horses developing clinical signs that were known or suspected to be caused by the virus. Sadly, at least 13 horses died. The outbreak spread to at least 10 US states as well as parts of Canada.
Threats in the UK
The ever-present threat of new or exotic diseases could prove devastating for horses in the UK that have not been exposed to such infections before. There are also a limited number of contagious equine diseases already here that we need to be aware of and to try to control.
Respiratory infections are usually considered the most threatening type of contagious disease that can spread among our horse population. These include the equine influenza virus, equine herpes virus and strangles. The characteristics of these diseases are very different, so preventative strategies have to be planned accordingly.
Equine influenza is a major and economically important cause of acute respiratory disease in horses. It is highly infectious, because large amounts of virus are sneezed and sprayed from an infected horse as he coughs, similar to someone with a cold.
The incubation period is short — usually two or three days. This means that the virus can spread rapidly, especially as infected horses can shed the virus for up to 10 days.
Another challenge with flu viruses is that they can mutate and change their characteristics. This means that the vaccine needs to be updated regularly to ensure that the currently prevalent strains are included.
The extensive use of vaccines in the UK has reduced the incidence and severity of equine flu outbreaks.
Continuing the protection depends on an effective vaccination programme, with as many as possible of the equine population being properly vaccinated.
Outbreaks still occur and these can be controlled by rapid diagnosis. The Animal Health Trust (AHT), a charity established with the aim of fighting disease and injury in animals, has an excellent scheme whereby free samples can be sent to its lab by your vet, which is a very useful surveillance measure.
Silent carriers
Strangles is another highly contagious infection that is regrettably all too common.
The disease is very different from equine flu. Strangles is caused by bacteria that sometimes produce obvious abscesses, but on other occasions much more subtle respiratory signs. The challenge is that the disease is often introduced into a yard by a carrier animal, which can show no clinical signs but is still able to infect other horses.
Equine herpes virus is probably the most widespread of these infectious diseases. There are a number of different types of equine herpes viruses, but types 1 and 4 are the most important.
Infection by equine herpes virus-4 usually produces respiratory disease, whereas type 1 can also result in abortion, the birth of sick foals and neurological disease. Outbreaks of equine herpes virus-1 neurological disease in the past year have highlighted the significance of this infection.
The verdict on vaccination
Vaccination for flu is relatively routine. Although there is a herpes virus vaccine available, it is not thought to provide proper protection against the neurological form of the disease.
A vaccine now available in the UK can help to reduce the severity of the signs of strangles, but it is not used routinely and should be discussed with your own vet.
Vaccination is beneficial, but it is by no means the only answer to protection against infectious diseases. Continuous, sensible, protective precautions and proper management are equally important in the battle against bugs.
This article was first published in Horse & Hound magazine (31 July 2014)
