Theodore Roosevelt, 1903

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Monday, June 22, 2015

Horse Care -- Strangles (Equine Distemper)

A reader wrote asking about Strangles. While I am not a veterinarian, I will attempt to answer her questions as to what is Strangles, what are the warning signs, the treatment, and the prevention measures, for horse owners?  

Strangles, also known as Equine Distemper, is a contagious upper respiratory tract infection. The name "strangles" was coined due to the strangling breathing sounds made by affected horses.

Caused by the enlarged lymph nodes of the jawbone, it is caused by a bacterium called streptococcus equi. Strangles is enzootic in domesticated horses worldwide.

The contagious nature of the infection is a real concern for horse owners because the disease is spread when the nasal discharge or material from the draining abscess contaminates pastures, barns, feed troughs, stables, etc. 

While direct contact between horses is the most common way that strangles is spread, it can also be spread by contaminated equipment. Improperly cleaned and shared buckets, stalls, and tack can spread the disease between horses. Fortunately, the bacteria dies fairly quickly in the environment.

Warning signs include fever, heavy nasal discharge, a swollen or enlarged lymph nodes in the neck and throat-latch, and stop eating.

The first signs of strangles are poor appetite, depression. and a high fever,

Owners will also notice a thin, watery discharge from the horse’s nostrils. This discharge quickly turns thick and yellow. The horse’s upper respiratory lymph nodes become enlarged, most noticeably the ones between the jawbones. These can even abscess.

My recommendation is if you suspect that your horse has Strangles, call your veterinarian immediately. 

Let him or her come out to confirm the presence of the disease, and set a course of treatment. Remember, the sooner a positive diagnosis is reached, the less "down time" the stable will have to tolerate.

If your horse was stabled near one who had strangles at a show or rodeo, it is reasonable to treat it with antibiotics for at least six days after exposure. This is because horses usually don’t show the first signs of the disease for two to six days.

Strangles is not usually fatal to horses, but it can be.

The disease is usually acquired after exposure to another horse that is shedding the streptococcus equi bacteria, either during or after its own bout of the illness.

This commonly occurs when new horses are introduced to an established herd.

Although the infectious horse may no longer show signs of strangles, it can still spread the bacteria. Around twenty percent of horses remain contagious for a month after all symptoms vanish.

Strangles can affect horses of any age, but younger and elderly equines are more susceptible. Young horses may lack immunity to the disease because they have not had prior exposure, while elderly horses may have a weaker immune system.

The treatment of strangles is dependent on the stage of the disease.

Once a horse is exposed to the bacteria, it will begin to show symptoms in two to six days. If left untreated, it will develop abscessed lymph nodes within one to two weeks after the onset of illness. These lymph nodes will rupture and drain, and the drainage is highly contagious. Most horses will recover, but around ten percent of untreated horses die, usually from a secondary infection which causes pneumonia.

Rarely, the abscesses will spread to other parts of the horse’s body, such as the lungs, internal organs, or even the horse’s brain. This condition is called “bastard strangles.” It is uncommon and is usually fatal.

Precautions to limit the spread of the illness are necessary and those affected are normally isolated.

To control the spread of the strangles bacteria, any new horse with a vague or unknown health history should be isolated for 4 to 6 weeks before being added to the general population of the stable or paddock. Yes, an isolation period of 6 weeks is usually necessary to ensure that the disease is not still incubating before ending the isolation.

Nasal swabs can ascertain whether the horse is shedding the streptococcus equi bacteria, but because affected horses shed the bacteria sporadically, one swab test is not enough. Three nasal swabs over a period of seven days are required before it can be assumed that the horse is negative for strangles.

As with many streptococcal infections, penicillin or penicillin-derivative antibiotics are the most effective treatments. Also, if a horse begins antibiotic treatment in the early stages of the disease, lymph node abscesses can be prevented.

Supposedly old veterinary practices warned against using antibiotics for strangles because of the suspicion that it could cause bastard strangles, which has a much higher mortality rate. But, the problem with that is that it hasn't to be proven true or not.

When horses are treated with antibiotics in the early stages of strangles, they will recover unless the antibiotics are not given in the correct amounts or are stopped too soon. Either way, if the horse is on antibiotic therapy -- it must be isolated from the rest of the stable and herd to prevent the spread of the illness.

After an abscess has burst, it is very important to keep the wound clean.

It cannot be emphasized enough, once lymph nodes have enlarged and become abscessed, antibiotic treatment will only prolong the horse’s illness.

So if the abscess has not burst on its own, it is believed that it is better to allow the abscess to open -- which means that a veterinarian may have to lance it so that it may drain.

The best treatment at this point is to flush the drainage site. A diluted povidone-iodine solution has been used with good results to disinfect the open hole, flushing the inside with a syringe tipped catheter or with a teat cannula, followed by gentle scrubbing to keep the surrounding area clean.

After that, keep the area as clean as possible and maintain strict isolation of the ill horse.

Complications can occur. Possible complications include the horse becoming a chronic carrier of the disease, asphyxia due to enlarged lymph nodes compressing the larynx or windpipe, bastard strangles (spreading to other areas of the body), pneumonia, guttural pouches filled with pus, abscesses, purpura haemorrhagica, and heart disease. The average length for the course of this disease is 23 days.

The good news is that prevention measures can be taken. Strangles can also be controlled by vaccinations. Although modern vaccines are more effective than those of the past, providing better protection with fewer side effects, they are not a complete guarantee against the disease.

Still, vaccinated horses tend to have a less severe illness if they do contract strangles. Horses cannot contract strangles from the vaccine itself, since it is made from only parts of the pulverized bacterium.

Both intramuscular and intra-nasal vaccines and isolation of new horses for 4 to 6 weeks, immediate isolation of infected horses, and disinfection of stalls, water buckets, feed troughs, and other equipment will help prevent the spread of strangles. As with any contagious disease, hand-washing is a simple and effective tool.

Strangles is a highly contagious disease. It can be terrifying to those running boarding stable for good reason because of how fast it spreads. But like with anything else, the more horse owners know -- the better prepared one will be when dealing with this.

As I said previously, I am not a Veterinarian. But still, I do hope this helps as it is compiled from various sources. 

Tom Correa

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