Sometimes horses become depressed and feverish. They develop swollen glands around the head that start oozing yellow liquid. This condition is called strangles.

• Strangles is one of the most important diseases in horses worldwide.
• It spreads easily from one horse to another and is caused by the bacteria Streptococcus equi.
• Strangles occurs in horses of any age, but is most common in horses less than 2 years old.
• Foals younger than 3 months old are protected by colostral antibodies received from their mothers in the milk.
• Some recovered horses develop a temporary immunity, but South African research indicates that immunity doesn’t last for longer than 6 months after an infection.
• The bacteria can survive for up to 48 hours on items such as tack and overalls, and for up to 2 months in water. So keep an eye on water troughs!
• It can survive for 2 to 3 weeks on pastures in summer and longer under wet conditions, so consider a pasture to be contaminated for at least a month.
• The infection is spread mainly by direct contact between an infected animal and a susceptible one, and can also spread via contaminated drinking water.
• Animals begin shedding bacteria 2 to 9 days after the fever has abated.

SYMPTOMS

Signs appear 3 to 14 days after exposure to the bacteria.

The initial sign is a fever spike (40°C), which then subsides for several days until the lymph nodes (glands) begin to enlarge with pus and cause the classic symptoms:

• Fever, no appetite, depression
• Enlarged lymph nodes (glands) around the head. The horse may have difficulty breathing because the swollen glands close their airways (hence the name Strangles).
• Enlarged lymph nodes become abscesses which mature and exude thick yellow pus.
• A clear nasal discharge, becoming thick and yellow.

The disease spreads rapidly, and most horses in a group are affected.

Thankfully, very few horses die from strangles. The classic clinical signs cause a strong suspicion. Diagnosis is confirmed by culture of swabs taken from abscesses.

TREATING AN OUTBREAK

Management should include separating animals having abscesses (in the infective phase) to reduce the severity of an outbreak.

• Treatment includes pain and fever management and nursing.
• Using antibiotics is a contentious issue.
• When there’s an outbreak, horses are divided into three groups: those that have fever, those draining abscesses, and those that don’t yet have symptoms.
• Each group is handled separately.
• If there’s an outbreak, consult your vet for a specific treatment programme.

PREVENTION

• Techniques typically employed for any contagious disease should be used to prevent and manage strangles.
• Preferably isolate affected animals (if they have a cough, nasal discharge and/or swellings) immediately and disinfect equipment, feed and water containers.
• Monitor at-risk horses’ temperatures every day and separate all horses that display temperature spikes.

Remember: shedding doesn’t begin for 1 to 2 days after the fever spike so this may prevent further spreading.

• Exposed but healthy horses should not travel to other equine facilities for at least 1 month after exposure.
• Tell local horse owners, and local horse authorities about the outbreak.
• Horses newly introduced onto a farm should have a thorough previous medical history and be kept separate.
• Their temperature should be monitored for 2 weeks.
• A horse displaying classic symptoms should be kept separately and a swab culture should be taken.
• People caring for infected horses shouldn’t handle healthy horses or only do so after disinfecting themselves.
• You could also work with infected horses only at the end of each day.
• Disinfect hands, water troughs and so on with effective compounds such as chlorhexidine and gluteraldehydes.

There is a vaccine for strangles – it’s injected into the lip. But remember that the vaccine doesn’t totally prevent the disease from developing. Rather, it minimises symptoms and prevents the oozing abscesses that cause rapid spread and outbreak of the disease.

Also read:
How to buy a horse
How to feed your horse
Being on top of a horse emergency
Treating tendon injuries in horses
Dealing with worms in your horses

• This article was written by Dr. Marc Walton and first appeared in Farming SA.