Strangles

Strangles is equine specific.² Caused by the bacterium S. equi, the first sign of infection is a fever, before leading to the formation of abscesses in the lymph nodes of the head and neck.^1,3 Some animals will show only mild symptoms, while some others may become very sick.¹ The mortality rate is up to 10%.^1,2

It is therefore vital you know the signs and how it spreads, so you can minimise the impact strangles could have on your horses and yard.^2,4

Fever is the first sign of strangles¹

When a horse develops a fever, it is time to act.^2,6
While strangles is being confirmed,
put biosecurity measures in place
and discuss vaccination with your vet.⁴

How does strangles spread?

Strangles mythbuster

Strangles only spreads
via direct contact
between horses.

While strangles can pass from horse to horse by
direct contact, it also spreads indirectly via water
troughs or contaminated equipment, for example.^1,4
This is why biosecurity measures and vaccination
are so vital in the face of an outbreak.^1,4

Routes of infection

Direct contact

Horses touching noses is a common route of infection.¹ It is therefore important to keep infected horses away from other horses during an outbreak.^1,4

Indirect contact

Illustration showing indirect transmission of strangles

Contamination of the environment and equipment such as grooming kits, tack, feed, transport and even handler’s clothing or hands can all act as sources of transmission.¹ Water troughs are also a common source of infection, with strangles bacteria able to survive for over 1 month in water.¹ It is therefore important nothing is shared between infected and uninfected horses during an outbreak.^1,4

How strangles progresses in a horse^1,4,6

How strangles progresses, from exposure through fever and clinical signs to long term carriers

What happens when horses are infected with strangles?

Strangles can spread quickly and easily between
horses, so act fast with biosecurity measures
and vaccination to stop the spread.^1,4

FAQs – Your questions answered

What are the clinical signs of strangles?

First sign:^2,6

Fever (body temperature >38.5^oC)

Other signs:^2,6

Nasal discharge
Soft, moist cough
Depression
Inappetence
Abscessation of the lymph nodes in the head and neck (and other body sites in rare cases)
Respiratory noises due to impeded airflow

My horse has recovered, why could it still be infectious?

All horses have two guttural pouches, one either side of the head.⁶ When S. equi enters the guttural pouch during disease, it remains here in approximately 10% of recovered horses.¹ These ‘carriers’ look healthy, but can also spread strangles to other horses.⁵

References

Boyle et al. J Vet Intern Med. 2018;32:633-647.
Rask E, et al. Animals (Basel). 2025;15(24):3584
Gröndahl G, et al. Equine Vet J. 2025: doi: 10.1111/evj.70125 (Online ahead of print).
Rendle D, et al. Equine Vet Educ 2025;37:90–97.
McGlennon A. et al. Equine Vet J. 2025; 58(2): 533-548. doi: 10.1111/evj.14558
British Horse Society. Available at: https://www.bhs.org.uk/horse-care-and-welfare/health-care-management/horse-health/equine-diseases/strangles/ (Accessed July 2026).

STRANGLES IS HIGHLY CONTAGIOUS¹
KNOW THE SIGNS AND HOW IT SPREADS

Fever is the first sign of strangles¹

How does strangles spread?

Routes of infection

Direct contact

Indirect contact

How strangles progresses in a horse^1,4,6

What happens when horses are infected with strangles?

FAQs – Your questions answered

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STRANGLES IS HIGHLY CONTAGIOUS1 KNOW THE SIGNS AND HOW IT SPREADS

Fever is the first sign of strangles1

How does strangles spread?

Routes of infection

Direct contact

Indirect contact

How strangles progresses in a horse1,4,6

What happens when horses are infected with strangles?

FAQs – Your questions answered

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STRANGLES IS HIGHLY CONTAGIOUS¹
KNOW THE SIGNS AND HOW IT SPREADS

Fever is the first sign of strangles¹

How strangles progresses in a horse^1,4,6

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