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Equine Diseases

Equine Strangles:
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Just the word “Strangles” can strike fear into the hearts of horse owners. Despite the fact that it is fatal only about 3% of the time, it remains a dreaded disease. Its highly contagious nature and obvious and severe symptoms are difficult to ignore.

Strangles is spread by a bacterium called Streptococcus equi. The bacteria gains access to the horse through the mouth or nasal area, where it grows on the horse's tonsillar tissue. It then spreads to the lymph nodes in the back of the throat, leading to an infection accompanied by a fever, loss of appetite, and general malaise. Generally, disease occurs within 3-14 days of exposure to the bacteria. Over time, the lymph nodes will fill with pus, and then rupture and drain. As the lymph nodes swell, they become large and painful. The horse will often stand with his neck stretched out in an attempt to relieve the pressure. The horse may also cough or develop loud and difficult breathing due to the pressure on his throat. The sounds the horse makes while breathing are what gave rise to the name “Strangles”. In up to 10% of cases, the bacteria may invade lymph nodes in the chest and abdomen, resulting in serious and life-threatening disease. This is termed disseminated or “bastard” strangles and is much more dangerous than the disease’s normal course.

Strangles is almost always contracted from another horse. The disease is very contagious, and the bacteria may survive in the nasal passages, throat, and guttural pouches of the horse for weeks to months following recovery. These horses often spread the disease as people think they are “cured” and allow them to intermingle with other horses again. Touching noses, sharing water sources, and sharing feed sources are all avenues by which the Strangles bacteria travels from one horse to the next In addition, it can be spread by buckets, feeding equipment, bits, and people who handle the horses . The Strangles bacterium is generally only a health danger to the horse and does not cause disease in humans. Usually young horses are most severely affected as they lack immunity to the disease. The disease is most likely to be fatal in foals, especially those who did not receive good colostral immunity from their dams.

The Strangles bacteria can live for significant lengths of time on exposed surfaces. It can survive 3 days to one week on stall surfaces, soil and other places. In freezing weather it can persist indefinitely, though. Water can be a significant source of infection as the bacteria can survive in water for up to six weeks. Most stables can be safely repopulated after a Strangles outbreak, but care should always be taken to clean and disinfect the water sources prior to introducing horses again.

So what if your horse DOES develop this disease? Well, first of all, care is directed at keeping the horse comfortable. This may include non-steroidal anti-inflammatory drugs such as Ban amine for pain and fever reduction, liniment or hot-packing of abscesses, and sometimes antibiotic use. Antibiotic use is often avoided in Strangles cases, because it is difficult to penetrate the abscess with antibiotics, and antibiotics can actually make it take more time for the horse to recover. In addition, while horses who recover from Strangles without antibiotics will have long-standing immunity to the disease, horses treated with antibiotics may not. When antibiotics are used, Penicillin given early in the course of the disease is the best option. If the abscesses are so large they interfere with breathing or swallowing, they may be lanced and drained by your veterinarian. In these cases, flushing of the abscesses with an iodine solution may also be needed if possible.

In many ways, the most difficult part of dealing with Strangles infections is to prevent the spread of the disease to other horses. Meticulous care should be used to prevent spread of the disease to other horses. The affected horse or horses should be isolated. The area where they are housed should be considered contaminated until 1 month following the horse’s recovery. Isolation and care to prevent any contact of the affected horse or any equipment used with him from coming into contact with other horses on the farm is the only way to prevent the spread. Once Strangles has been diagnosed on the farm, no horses should come in or out until the premises are clean. This means minimally until there are no new cases for three weeks. However , three negative nasal swabs on all affected horses is the “gold standard” for calling a barn “clean” from Strangles.

To prevent Strangles outbreaks, horses newly arriving to a barn should be isolated for a period of 2 to 3 weeks. Horses that have shown no symptoms after 3 weeks are at low risk of spreading disease, although there are occasional horses that have no signs but may still spread the disease. If you are traveling with your horse bring your own buckets, feed containers etc if possible. If it is not possible, then disinfect feed and water containers prior to use. Also, ascertain that the stalls being used are disinfected in between horses. Minimizing stress on your horse will also help protect him from disease.

Vaccines exist but are not without their issues. The intra-muscular strangles vaccine is associated with painful inflammation at the injection site, and vaccine reactions. The intranasal vaccine is safer but must be properly administered or else it is ineffective. In addition, because it is a live vaccine, it is possible to cause abscesses if appropriate care is not taken when the Strangles vaccine is administered along with other vaccines. Both vaccines require boosters ever 6 months for optimal immunity. Vaccinating once an outbreak has begun is not recommended as this increases the risk of a fatal complication called purpura hemorrhagica.

The good news is that most horses will make an uneventful recovery from Strangles, and acquire a lasting immunity to the disease. If you think your horse may have Strangles you should always contact your veterinarian right away.


Denise Bickel DVM
Whole Horse Veterinary Services
Phone # 517-474-4050
Fax # 517-764-7710
3906 Seymour Rd
Jackson, MI 49201


Hours--Mon, Thurs, Fri from 11 am to 8pm, and Sat and Sun 10 am-4 pm

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