Strangles is one of the most common equine diseases in horses in the UK. It is a highly contagious infection of the upper respiratory tract caused by the bacteria Strep. equi (Streptococcus equi subspecies equi). Horses, ponies and donkeys of all types and ages can be affected, but young horses typically develop more severe signs.
Signs of strangles
The signs vary between mild to severe and are not always typical.
A horse suffering from strangles will typically have a temperature (above 38.5°C), depression with a loss of appetite and thick, yellow mucus draining from both nostrils. Hot, painful abscesses may develop on the sides of the head and throat, which may burst and discharge pus. The horse may experience difficulty eating or extending his head, due to the discomfort in its throat, hence the name strangles.
Strangles can sometimes produce more subtle signs in a healthy adult horse, who may only display a slight short-term increase in temperature, a brief loss of appetite and a clear nasal discharge. But if you suspect your horse may have strangles, it should be immediately isolated and veterinary advice sought.
There are various lab tests available to confirm if a horse is suffering from the disease, which are important, since some animals (usually up to 10%) will be carriers and not show any signs of illness.
The best way to reduce spread is to spot the signs early.
Although strangles is rarely fatal, there may be complications in up to 20% of cases. The abscesses in the throat can cause difficulties with eating and breathing if they put pressure on the airway. Rare complications include bastard [metastatic] strangles, where abscesses form elsewhere in the body, and the immune system disorder purpura haemorrhagica.
How is strangles spread?
The bacteria are primarily transferred between horses by direct contact or shared environments such as water troughs, with discharge from any draining abscesses being highly infective. It can also be transferred via a third-party such as people’s hands or clothing, or tack and yard equipment. The strangles bacteria will not be blown far in the wind, unlike some viruses (such as foot and mouth) which can travel long distances by that route.
To reduce spread of infection, it is important to isolate any horse suffering with the condition and undertake good hygiene precautions and suitable biosecurity to prevent transferring the infection to others. It is good practice to isolate new equine arrivals to reduce the risk of infection — ask your vet for advice.
The incubation period is up to 14 days (usually 3-10 days), but abscesses can take up to a week to appear after that. The condition typically lasts about three weeks, if untreated.
Around one in 10 former sufferers appear outwardly healthy, while carrying bacteria. These ‘carriers’ can intermittently shed bacteria for months — or even years — afterwards, meaning they pose an on-going risk to other horses.
Most horses suffering from strangles just need good quality nursing, including rest and anti-inflammatories. Feed hay and hard feed on the floor to encourage drainage. Abscesses can be hot-packed to encourage them to burst, or your vet may lance them. The use of antibiotics to treat strangles remains controversial and is best addressed by your own vet on a case-by-case basis. Fresh air can help affected horses, but turnout can result in grazing becoming contaminated.
A new vaccine against strangles is currently in development and is expected to be available for use in 2020.
Unfortunately there is considerable and unjustifiable stigma associated with the condition, with rumours of outbreaks spreading like wildfire. Yards that have an outbreak are recommended to share the news openly with the local equestrian community, rather than trying to keep it under wraps, in order to prevent wider infection.
A yard with an outbreak of strangles should limit contact with external horses as much as possible. Isolation is important, but difficult to maintain, and should last for up to a month after the last case occurs. Again seek advice from your own vet.
Other recommended precautions include:
Disinfectant foot bath outside isolation stables and at the yard entrance
People looking after affected/isolated horses should change all their outer clothing and wash their hands before handling other horses
The strangles bacteria will be destroyed by a hot wash, so changing and washing clothes will reduce the risk of spread
Cases of suspected strangles should be taken seriously and horses should be isolated until proven not to have the disease
Monitor rectal temperature twice daily in all horses you are concerned about. A raised temperature may be the first clue that they may be about to develop signs
Let people such as the farrier, dentist, vet, saddle fitter, feed delivery man know before they come to the yard. They may prefer to make you the last visit of the day to avoid any chance of spreading the bacteria to other yards
Warn horse owners using adjoining fields or who ride close to the yard to keep their distance
Behave responsibly and avoid taking in-contact horses to shows where they may spread the disease to other horses and yards