Vet Expert - how to deal with Strangles

...with Heather Simpson of Glenythan Vet Group

Strangles is one of the infectious equine diseases which strikes fear into the hearts of owners - and along with Equine Flu - there have been cases in Scotland just as the spring competition season was starting this year.

Both are infectious, albeit in slightly different ways, both are always around - and this year Equine Flu in particular has seen a bit of an outbreak in the UK, something which hasn't happened for a few years.

Strangles, on the other hand, often presents a few cases every winter. But Strangles can now be vaccinated for, an option that was not available to owners previously. Equine Flu (and tetanus) has been vaccinated for over many years, and there are rules within equine organisations which restrict horse movement for those which are unvaccinated.

As the Strangles vaccination is relatively recent, equine vet Heather Simpson of Glenythan Vet Group explains here what Strangles is and why it is important to consider vaccinating for Strangles as well as Equine Flu.

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By Heather Simpson, BVMS, MRCVS

What is Strangles?

Strangles is a disease of the upper respiratory tract of horses which often causes fear in many horse owners.

Worldwide it is one of the most common infectious diseases of equines and can affect any horse, pony or donkey. It is caused by Streptococcus equi equi which is a highly contagious bacteria.

Spread of disease

Bacterial spread can be direct or indirect:

• Direct transmission occurs when horses come in to contact with each other

• Indirect transmission occurs when infected horses shed the bacteria in mucus or pus, which lands on surfaces such as buckets or human clothing, which is then inhaled by another horse

Direct transmission risk. 

 The bacteria can survive for several weeks in water, so sharing troughs and buckets is a high risk for infection spread.

The incubation period, which is the time between infection and clinical signs developing, is very variable but is most commonly between three and 21 days.

Above: Nasal discharge (pus) from the nostrils in Strangles.

Clinical signs:

Typical symptoms:   

•             Dullness/lethargy                                                                

•             Fever/high temperature (over 38.5˚C)                            

•             Nasal discharge, usually thick, creamy or yellow (above)    

•             Swellings around jaw - these are lymph nodes which can become abscessed and release thick pus

•       Reduced appetite, reduced water intake, difficulty swallowing (known as dysphagia)

•     Cough        

•   In very severe cases, the swelling can cause respiratory obstruction or difficulty breathing

 Above: photo showing submandibular swellings.

In approximately 10% of cases infected horses go on to

become carriers of Strangles

This means they show no clinical signs of disease, but they excrete the bacteria infecting other horses. In most of these cases chondroids, which are solidified masses of pus, are found on endoscopy of the guttural pouches.

How is Strangles confirmed?

If you suspect a case of Strangles, isolate the affected horse to minimise disease spread and contact your vet.

Your vet may be highly suspicious of Strangles based on the clinical signs, but will confirm the diagnosis with laboratory testing.

Treatment

Your vet will give you advice tailored to your specific case, usually supportive care and medical treatment. Antibiotics are not used in every case, generally only if there are complications.

Vaccination

The vaccine available for Strangles is effective at reducing the clinical signs seen following an infection, reduces the likelihood of abscesses developing which means the horse is less likely to become a carrier of the disease and reduces bacterial shedding.

This means a vaccinated horse is less likely to contaminate the environment and infect other horses. Therefore, vaccination does not replace other prevention strategies, but is beneficial in reducing disease.

The vaccine is given by intra-muscular injection, and a primary course of two injections given four weeks apart is followed by booster injections at up to 12-month intervals.

Prevention

Good biosecurity is essential. There are many ways to reduce the likelihood of disease occurring or spreading on your yard.

Some prevention strategies are:

• Quarantine new horses moving onto a yard for at least 2 weeks

• Pre-movement testing. This often involves blood testing your horse or pony, but can also involve swabs being taken, or endoscopy of the guttural pouches

• Avoid sharing equipment

• Do not allow nose-to-nose contact with horses of an unknown health status

• Remember people are involved in in-direct transmission

• Vaccination

These strategies are useful for preventing many infectious diseases, not only Strangles.

Preventative measures will reduce the likelihood of disease, but outbreaks can still happen.

All yards should have a plan in place which can be implemented if a disease outbreak occurs. If you require assistance producing a control plan, please contact your vet who will be able to help.

Contact Glenythan Vet Group on (01358) 720223 or (01651) 806212 or go to https://www.glenythanvetgroup.com