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Vaccinations – are they necessary?

Horses are the most susceptible animal to this disease, 300 times more susceptible than your dog!

Vaccination schedule: two vaccinations four weeks apart, then a year later, then every few years (2-5) depending on age and vaccination history. Tetanus and strangles vaccinations are often combined.

How does it happen?
Just like humans, horses can too develop tetanus. They become infected from soil contamination, where spores of the organism Clostridium tetani enter the body through broken skin. Often wounds, abscesses, umbilical cords of foals and mares after foaling are the most common times we will see tetanus. However, even mud-fever can be a cause.

Among all the animal species horses are considered the most susceptible to tetanus, with them being 10x more susceptible than humans and 300x more susceptible than dogs. You would have thought with horses living outside and how prone they are to getting wounds and abscesses they would have developed a better natural immunity to this disease, but evolution sometimes is surprising.

What does it look like?
The incubation time is 3 days to 1 month after a horse is initially infected. This is good to keep in mind for those times you find a small old scratch on your horse; it is worth getting protection from this disease if they are unvaccinated or vaccination history is unknown. If you have an unvaccinated horse and they manage to get a wound or abscess, we have an antitoxin which acts immediately and lasts for 4 weeks. This will give you enough time to start the vaccination course, so your horse is covered now and in the future.

Clinical signs of tetanus include:

  • Head spasm and neck spasms
  • Salivation
  • Difficulty swallowing
  • Restricted jaw movement (lock jaw)
  • Generalized Stiffness (classic ‘saw horse’ stance)
  • Difficulty moving or lowing head/neck
  • Ears erect and immobile
  • Third eyelid protrusion

Can we treat it?
The treatment for horses with tetanus is intense as they often can’t eat or drink. It is also quite expensive and has a poor prognosis with the documented survival rate ranging from 20-30%. Prevention is much easier, successful and cost effective!

Vaccination schedule: three vaccinations two weeks apart, followed by a yearly booster. Boosters can be given six-monthly in high risk situations. Tetanus and strangles vaccinations are often combined.

How does it happen?
Strangles is characterized by an acute upper respiratory infection and lymph node abscessation. It’s an infectious disease that spreads via nasal discharge and puss from abscesses from horse to horse or via objects such as hands, clothes, bedding, boxes, grooming gear, water troughs, horse floats, gumboots, quad bikes, fence railings and the list goes on! Strangles is caused by the Streptococcus equi equi bacteria, which upon infection moves to the lymphnodes in the throat area where they sit and proliferate (grow in numbers).

What does it look like?
The incubation period for strangles is between 3-6 days. Strangles can present in different ways. Even though the most classic presentation is fever with lymph node abscessation, a horse can also present only with fever, decreased appetite and some slight nasal discharge. It is also possible that recovered horses can become lifelong carriers. A carrier doesn’t usually show signs of illness at all. They can however spread the bacteria to other horses from time to time.

Once the Streptococcus equi equi bacteria sits in the lymphnodes, they create an abscess / abscesses, which then need to mature and burst open to get rid of the bacteria inside of it. Until that time the abscesses tend to restrict air passage to different degrees. In rare and extreme cases a tracheotomy (making a whole in the trachea) is needed to help a horse breathe.

A horse with strangles can have either spikes of fever or ongoing fever, depending on the stage of the disease. Their throat is swollen and hurts, which makes eating and drinking painful and difficult. Horses with abscesses due to strangles need a lot of tender love and care, anti-inflammatories and painkillers to keep them eating. Once abscesses have matured and drained, the normal course of disease usually takes 10-14 days to resolve.

Strangles is primarily a disease of the young but horses of any age without previous infection or immunization may be affected.
Diagnosis can be made on clinical signs and/or a nasal swab and/or pus from draining lymph nodes.

Can we treat it?
Antibiotics aren’t effective enough to resolve the abscesses, allthough they do slow the maturation process down. This lengthens recovery time and has proven to cause a risk of the bacteria having time to spread through the body to other lymphnodes where they cause abscesses too. This creates a serious situation because antibiotics don’t resolve those abscesses either, but if they burst the puss can end up anywhere in the body, causing infection in the blood as well, which leads to death.

The best way to treat a horse that has strangles is to give it anti-inflammatories and painkillers to make sure they keep eating and drinking. The abscesses need time to mature and burst. Once they do, the abscesses can drain. They need to be flushed and kept clean every day until they have healed up. Fever usually breaks once the abscesses have burst and drainage is facilitated.

The most important thing when you have a horse with strangles is to immediately apply appropriate isolation and monitoring measures. Strangles is very infectious, so by keeping the infected horses islated from other horses the disease can be contained. Do not attempt to transport a horse with strangles, or a horse that has been in contact with another horse that has strangles. All horses on the same property need to be temperatured twice a day. As soon as another horse on the property develops a fever it needs to be isolated as well. By giving antibiotics on the first day of fever, before abscesses have developed, the bacteria can still be defeated. A vet can take nasal swabs or nasal flushes from all horses that have been in direct or indirect contact with the horse that has strangles to determine which horses have been infected.

People who come into contact with horses that have strangles are not allowed to have contact with other horses and are not allowed onto other properties until they have showered and put on lean clothes and shoes/boots. Areas that have come into contact with the infected horse need to be sanitized with a disinfectant, e.g. Virkon, to help prevent further spread. Isolation measures have to be enforced until at least 4 weeks after the last horse has recovered.

Some horses may become carriers. The only way to find out whether a horse is a carrier is by looking at their guttural pouches.

We do not recommend vaccination in the face of an outbreak or if your horse has been in contact with a strangles horse. By vaccinating a horse that may be incubating strangles, a disease called pupura haemorrhagica can develop which can have devastating consequences for the horse so please talk to your vet for advice on this.

Equine Herpes Virus
Vaccination schedule: pregnant mares need to be vaccinated at 5, 7 and 9 months of pregnancy. If pregnant mares are part of a herd, the whole herd needs to be immunized. In young horses: from 4 months of age, then 3-4 weeks later, 6 months later, and then annually.

How does it happen?
Equine Herpes Virus (EHV) can cause several different diseases in horses. There are different strains of EHV. EHV1 isn’t as common as EHV4, but is a little more aggressive and can cause respiratory infection, abortion and neurological disease. EHV4 is more common and usually only causes pneumonia. Commonly 80-90% of horses come into contact vith EHV4 before the age of 2. One of the reasons is that when the horse recovers from it, the virus can actually stay in the body inside certain cells, where the EHV becomes dormant. The horse will not get sick anymore, but can shed the virus to other horses at different life stages. This is why it’s impossible to know which horses might actually pose a risk for pregnant mares for example. The virus is spread via particles from the respiratory tract, which can go from horse to horse or via materials such as hands, clothes, bedding, boxes, grooming gear, water troughs, horse floats, gumboots, quad bikes, fence railings and the list goes on! When a horse coughs or sneezes the virus can spread through the air over several meters distance. When a mare gets infected and aborts, the fetus, fetal membranes and placental fluids are very infectious and other horses, especially pregnant mares, should not come near the infected area.

What does it look like?
Respiratory infection can present as the sniffles, a proper cold or just some nasal discharge. Younger horses often show more obvious signs of illness than adult horses. An EHV infection can even go unnoticed in adult horses.

Abortion due to EHV usually happens in the last trimester of pregnancy, which can be very frustrating. However, the virus could already have been introduced months prior to the abortion.

When the virus affects the vessels in the brain this can create oxygen shortage, which causes damage to brain tissue. This leads to neurological symptoms, such as ataxia or even paralysis.

Especially young horses, competition horses and pregnant mares are at risk of infection and disease. Young horses are more sensitive to the virus. Horses come together at competitions and rallies, and horses that have been transported and are entering competition may have a temporary lapse of immunity. EHV might therefore spread more easily at such events. Pregnant mares are not at any greater risk of infection than other adults, but because abortion is so absolute they should be especially considered.

Can we treat it?
Horses usually recover from respiratory infection seemingly uneventfully.

If a mare gets infected only a few weeks before giving birth, the foal may be carried to term, but unfortunately these foals die shortly after birth.

Recovery from neurological disease may take months. When a horse becomes recumbent for over 24 hours the prognosis becomes grave and euthanasia must be considered for welfare reasons.

Important note: For optimal protection of pregnant mares we advise that all horses in the same herd are vaccinated to generate herd-immunity.

Management advise: Preferably keep pregnant mares in small groups, separate from young stock and competition horses. If abortion has occurred before, let all mares give birth in a separate area to prevent any potentially infected fetal material from infecting other mares.

Vaccination schedule: two vaccinations four weeks apart, followed by a yearly booster. Previously vaccinated pregnant mares need a booster no later than 6 weeks before foaling. In pregnant mares that haven’t been previously vaccinated, start no later than 10 weeks before foaling. For foals start from 4 months of age with two vaccinations four weeks apart, followed by a booster 6 months later, then yearly.

How does it happen?
Salmonella is the most common bacteria that causes diarrhoea in horses. The bacteria can survive in the environment for long periods of time. It can be spread by birds, rhodents or other horses. Horses can be carriers for Salmonella, which means that they can carry the bacteria without getting sick. A carrier can spread the bacteria via its faeces, especially if the horse becomes stressed and immunity goes down. Examples of stress factors are transport, overcrowding, changes in feed regimen, intense physical activity, antibiotic treatment, surgical treatment, etc.

Horses can pick up the bacteria via infected food or water, or if the bacteria is present in the environment (the grass, objects, etc). Hygene is important and birds should not be allowed in drinking water. Horses that are sick from Salmonella excrete large amounts of bacteria. The excretion decreases gradually over time and ceases, unless the animal has become a symptomless carrier.

What does it look like?
Clinical signs and severity vary. Carrier horses show no symptoms. Infected foals are more prone to clinical disease than adult horses. Diarrhoea, often severe and watery, is the most common symptom. Other symptoms are fever, colic and poor general condition. Diarrhoea caused by Salmonella can lead to more serious issues such as dehydration, septicaemia, endotoxic shock and death. Septicaemia can, particularly in foals, lead to arthritis/polyarthritis, and/or pneumonia. Laminitis is considered a possible complication of salmonellosis in horses. There is a suspicion that the bacteria’s endotoxins may play a role in the pathogenesis of laminitis.

Can we treat it?
It is a general perception that antibiotic treatment increases the risk for symptomless carriers. In addition, there is a risk that the symptoms may worsen since antibiotics disrupt the normal flora of the intestine. Therefore, uncomplicated cases of diarrhea are not treated with antibiotics. The most important part of the treatment is to maintain fluid- and electrolyte balance at the right level so the horse can have a chance to cope with the infection. Complications such as septicaemia can motivate antibiotic treatment.

Sick horses should quickly be isolated from other horses. Since the infection spreads through faeces from sick animals, it is important to consider how to handle faeces, bedding material etc. from premises where excreting animals are kept. Separate boots, clothes, forks, shovels, wheelbarrows etc. should be used in infected and uninfected areas respectively. Tools used in infected areas should also be cleaned/disinfected at regular intervals.

Salmonella survives well in the environment, which means that a thorough cleaning is necessary. It is important to start with a thorough mechanical cleansing, followed by disinfectant with proven efficiency against salmonella. High-pressure washing should be avoided since it creates aerosols that can spread the infection. Lastly, it is important to let the stable dry up thoroughly since moisture benefit and dryness disadvantage bacteria.

Vaccination provides protection against diarrhoea, septicaemia and polyarthritis.

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