Strangles

What Is Strangles?

Strangles is a contagious bacterial infection caused by an organism called Streptococcus equi equi. Infection is passed by direct contact – either horse to horse or via people and equipment. It cannot travel over any significant distance in the air, no more than a few meters. Strangles is not a notifiable disease. There are no statutory regulations as to how infection must be dealt with and vets have no power to control outbreaks, however there are recognised guidelines on how best to manage infectious outbreaks.

Signs and Symptoms

  • High temperature (often over 40degrees)
  • Off food and depressed in themselves
  • Profuse nasal discharge
  • Swellings around or under jaw which may discharge pus
  • Coughing
  • Difficultly breathing

Some horses do not show all these symptoms. Some may only show mild symptoms and some are much more severely effected.

Managing an Outbreak

When horses on your yard present with any symptoms of strangles it is important to isolate them immediately and contact us. We will perform a clinical exam including auscultation of lung fields and trachea and taking a rectal temperature. We will then take a swab of the snot to confirm strangles is the cause. It is not necessary to administer antibiotics in these cases, although strangles can be severe, it is self limiting and antibiotics can prolong disease and increase your risk of secondary complications such as bastard strangles or purpura. We will start your horse on non-steroidal anti-inflammatories to reduce your horses temperature and make it more comfortable and to reduce inflammation in the airways. Hot poulticing any abscesses that form around the jaw may be advisable. BEWARE the pus is very infectious! It is important to isolate all horses showing symptoms. Wear overalls and wellies that are easily disinfected between stables as clothing can be a carrier of infection. Disinfect all tack and brushes as these can also carry bacteria. Affected horses should not be allowed in nose to nose contact with each other. Once the swab has come back positive for strangles a traffic light system should be implemented. The RED group of horses are those that have had a positive sample for strangles. These should be isolated from all other horses, possibly out in a field far away from the working yard. The AMBER group of horses are those that have been in contact with the affected horses, perhaps out in the same field together, but have not yet shown any symptoms. The GREEN group of horses are those that have not been in contact with any affected horses and also have no symptoms. It is important to monitor all amber and green horses for signs of disease by taking a rectal temperature twice daily. Your yard should prevent any horse entering or leaving the yard until all horses are determined free of strangles.

When to Re-Open Your Yard

Once horses have recovered from infection they need to be assessed to ensure they don’t remain as carriers. In carrier horses the bacteria remain dormant in the guttural pouches, not causing disease to the host horse but shedding intermittently making that horse an infection risk to other horses. The best test for this is to insert a small camera via their nose into the guttural pouches and taking a sample of the fluid there. This is a routine procedure but is not cheap due to the time, equipment and personnel needed to perform this, as well as the stringent disinfection of personnel and equipment afterwards. You will only need one negative sample from a guttural pouch wash to determine your horse strangles free. Occasionally it may be necessary to flush the guttural pouches with antibiotics before the infection is cleared. Another method is to take 3 nasal swabs over a 2 week period and culture and look for the DNA, however this is a less accurate test and may result in carriers being missed. You will need all three swabs to come back negative for strangles to be determined strangles free. Once all red and amber horses on the yard have had negative tests you are able to re-open your yard to the public and allow horses to move on and off your yard.

Complications

There are several possible complications from strangles infection;

  • Bastard strangles: This is a potentially fatal form of strangles. The infection spreads to lymph nodes in the body creating abscesses within the body.
  • Purpura: This causes bleeding in the gums, mucosa and lungs of horses. It also causes swelling of the distal limbs, under the belly and the muzzle. This is also potentially fatal although treatment can be attempted using high doses of steroid and antibiotics.

Roo is a 7year old pony who presented with a satsuma sized lump under her jaw. She was a little quieter than normal but was eating ok and drinking normally. When examined she was very slightly reluctant when her lump was palpated and she had a very slightly increased temperature of 38.7degrees. Strangles was discussed as a possibility and we decided to take a sample of pus out of the abscess to test for the bacteria. The skin over the lump was clipped and cleaned to be sterile to avoid any contamination of the sample. A needle was then put into the abscess and the pus that came out was collected onto a swab and sent to the lab.

While we waited for the lab to send us results Roo was isolated from the other horses and her vigilant owner put footbaths and hand washes outside every stable.

The swab came back positive for strangles and Roo was isolated to a field far away from the stable block. Her owner made sure she changed and showered after every visit to see Roo. She checked her other horses for a high temperature twice a day for 21days until the incubation period of the infection was over. She disinfected everything Roo had been in contact with, the stable, tack and brushes included.

Once Roo had been clear of any clinical signs for three weeks we went and performed a guttural pouch wash. We put a small camera up her nose and into her guttural pouches. We put 50ml of sterile saline solution in to wash round the pouch and then took it back out again to send off to see if there was any bacteria left in the guttural pouches. Unfortunately this sample came back positive! Although she had no clinical signs she was still a carrier and was still an infection risk to the other horses on the yard! She continued in isolation for another 3weeks. At this point we went back again to perform another guttural pouch wash. This time, in addition to collecting samples we put penicillin antibiotics into each pouch to make sure, even if this sample came back positive, the existing bacteria in the pouches would be killed.

The second sample came back negative! Roo is now happily back with the other horses on the yard.