Your Horses Health and Strangles

What do you know about Strangles aka Strep. equii?  Strangles has been described in veterinary literature as far back as 1251, yet it is still one of the most commonly diagnosed infectious disease in horses around the world.  It has been called strangles because in the course of the disease the lymph nodes enlarge and push the pharynx, larynx and/or trachea of the horse and causing them literally to strangle and die from asphyxia.

In our area of Southeast Kansas and this practice, the disease is not seen abundantly but it is seen.  It does seem to show it's ugly head in cycles; one year being diagnosed more than another.  It is also seen more often in horses that travel often to shows, rodeos, breeders and trainers.  A few years ago I diagnosed several cases where a horse had been to a trainer and brought back the disease to the rest of the herd.  There were also cases in horses that were pastured adjacent to the trainer facility.  In most cases, all of these horses were not vaccinated for the disease, nor did the trainer require vaccinations prior to horses being brought to their facility.

Clinical signs of strangles include a sudden fever (>103 degrees), followed by a cough, nasal discharge and acute swelling and abscesses of lymph nodes located just under the jaw neck.  Horses become depressed and go off feed.  The lymph glands are painful and swollen within one week after infection.  Eventually these lymph nodes can become so large that they rupture and drains to the outside and into the guttural pouch.  Nasal shedding of the bacteria begins 2-3 days after the onset of fever and persists for 2-3 weeks in most cases.

While horse to horse contact is a concern in contracting this bacteria, indirect transmission by way of contaminated equipment and humans handling these animals also plays an important role.  The bacteria can survive in the environment in dirt or on a fence, in a stall, horse trailer, tack, for up to a week and in water (buckets, troughs) for up to 30 days.  While contaminated objects in a horses environment can serve as a source of infection, the bacteria does not live in the soil forever.  It is the recovered horse that  serves as the primary source of infection for weeks, months and sometimes years after it's recovery.

Some horses following recovery from the disease become asymptomatic carriers, shedding the bacteria periodically.  This carrier state may result from either incomplete drainage of pus from the guttural pouches and/or sinuses.  These horses appear well, sometimes with reports from owners of occasional coughing or nasal discharge. This carrier state can persist for months or even years, and undetected by owners.  These quiet carriers are often the primary source of infection and explain how some farms have recurring problems with S. equi.

How do we control is disease?  Traditionally 4 weeks of quarantine, +/- negative nasal swabs.  Remember though, carriers shed the bacteria intermittently and can have a negative culture for weeks or months.  Endoscopic examination of your horse's guttural pouches (where the bacteria resides) along with cultures for the bacteria would be more diagnostic and is certainly recommended if your farm has had persistent problems with strangles.  Additionally a PCR (polymerase chain reaction) test designed to detect DNA from the S. equi gene can be performed in conjunction with an endoscopic examination.

In order to limit the spread of strangles, it is important to recognize the disease early on and properly manage and segregate infected from uninfected horses.  Since each farm is different, your veterinarian is a key person to assess and help you manage an outbreak.  Of course it is best not to wait until you have a problem before you develop a plan for management.  Have your veterinarian inspect your premises, discuss with them your normal operations, so that a plan can be developed and ready to implement before you have a problem (emergency preparedness). Farms are often large enough so that a quarantine area can be set up apart from the main population, keeping sick from non-ill horses.

Besides quarantine, treatment and testing for carrier states following recovery, there are other steps that can help control an outbreak:

1. Movement of horses on and off affected premises should be stopped.  Segregate horses and implement hygiene practices immediately.
2. Rectal temperatures should be taken daily of all horses to help determine if new cases will develop.
3. Pastures where infected horses have been grazed should be rested for at least 4 weeks.
4. Implement a vaccination program
5. Work with your veterinarian.

As always, arm yourself with information and work with your veterinarian.  Working together as a team makes for one awesomely healthy horse!