Strangles is one of the most common diseases in horses in the UK — and there is a huge amount of stigma surrounding it.

What is strangles in horses?

“It’s an infection of the upper respiratory tract caused by the bacteria Streptococcus equi,” explains equine internal medicine specialist Philip Ivens MRCVS. “All equine types and ages can be affected, although youngsters tend to develop more severe signs.”

What are the signs?
“Classical strangles is characterised by a fever [above 38.5°C] accompanied by depression, loss of appetite and a thick, yellow mucus draining from both nostrils. Hot, painful abscesses may later develop on the sides of the head and throat, which burst and discharge pus. The horse may display signs of a sore throat, such as difficulty eating or extending his head.
“Atypical strangles is becoming more common, especially in healthy adult horses. Signs include a mild, short-term fever, sometimes accompanied by a brief loss of appetite, and a clear nasal discharge.
“These signs may be seen with other diseases, not just strangles. Immediate isolation and veterinary attention is essential.”

Can it kill?
“Strangles is rarely fatal, but can cause eating and breathing difficulties if the abscesses push on to the airway. Possible but rare complications include bastard [metastatic] strangles, where abscesses form elsewhere in the body, and the immune system disorder purpura haemorrhagica.”

How is it spread?
“Bacteria shed in an infected horse’s nasal discharge or abscesses can pass directly to a non-infected horse. Indirect infection occurs when bacteria are transferred on an object [a ‘fomite’], such as people’s hands or clothing, or tack and yard equipment. Ask your vet about necessary biosecurity measures.
“The incubation period is up to 14 days, but abscesses can take up to a week to appear after that. Sufferers can shed bacteria for up to six weeks after recovery and will pose a threat to other horses.”

Is treatment necessary?
“The use of antibiotics to treat strangles remains controversial and is best addressed by your own vet on a case-by-case basis. Most cases just need nursing care, including rest and anti-inflammatories. Abscesses can be hot-packed to encourage them to burst, or your vet may lance them.”

What is a carrier?
“Around 10% of former strangles sufferers appear healthy, but carry bacteria within their guttural pouches. These silent ‘carriers’ can intermittently shed bacteria for months — or years — afterwards, posing a risk to other horses. Identifying them is key to stopping further outbreaks and preventing spread of disease.”

Does vaccination work?
“Vaccination can be valuable when combined with good hygiene and biosecurity protocols. After a primary course, boosters are given every three to six months depending on risk level. Protection is not 100%, but vaccinated horses are less likely to contract the disease in an outbreak and will be less severely affected if they do. If a vet deems vaccination appropriate, it will be more effective if given to the whole yard.”

Read our exclusive feature in which we followed a yard coping with an outbreak of strangles in Horse & Hound magazine (24 October 2013)