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Strangles: A Funny Name for a Serious Equine Disease

Pet Column for the week of April 9, 2012

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Office of Public Engagement
2001 S. Lincoln Ave.
Urbana, Illinois 61802
Phone: 217/333-2907
Emily Schoenrock
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Source - Dr. Kara Lascola
Strangles is a bacterial infection that affects the respiratory tract of horses. Its odd name comes from the disease’s ability to cause the neck to swell so severely that the horse suffocates. First reported in 1251, strangles is now among the most widespread equine diseases in the world, and it is of great concern for equine owners and handlers.

Strangles, which is caused by the bacterium Streptococcus equi, is highly contagious. According to Dr. Kara Lascola, an equine veterinarian at the University of Illinois Veterinary Teaching Hospital in Urbana, the disease is often spread by asymptomatic shedders—horses that appear healthy but are infected and actively shedding bacteria.

Sometimes these shedders have recently recovered from an infection; horses may continue to shed the bacteria for up to six weeks after signs of the disease have ended. Horses that are newly infected and have not yet developed outward signs of disease may also be infective. In addition, some horses may harbor the bacteria for long periods and never show signs of active infection. These asymptomatic shedders facilitate the rapid spread of the disease within a horse population, creating an epidemiologic nightmare.

Transmission occurs through direct nose-to-nose contact between horses and also through “fomites,” objects that pass the bacteria indirectly via such as feeding troughs, tacks, fences, walls, and most importantly, handlers. The S. equi bacteria infect the respiratory tract of the horse and cause a thickened, clear to yellow-colored nasal discharge, enlarged lymph nodes in the head and neck, and fever. Anorexia, lethargy, and difficulty swallowing are also commonly seen.

The swollen lymph nodes of an infected horse frequently abscess. When this occurs, there is the risk of fluid draining into the air-filled space in the head called the “guttural pouch.” Even after a horse recovers from strangles, this space may harbor bacteria for months, making transmission to other horses possible.

The preferred treatment for a horse with a known strangles infection is to let the infection run its course while providing supportive care to improve the horse’s comfort level as much as possible. Recovery requires rest and easy access to food and water. If a fever persists, NSAIDS (non-steroidal anti-inflammatory drugs) can be used to lessen the symptoms. Occasionally the use of antibiotics is called for, but only in severe cases or when complications occur, such as the disease spreading to areas in the body not associated with the respiratory tract.

Vaccines available for strangles should not be considered an absolute preventative. In addition, adverse reactions to the vaccine can occur, particularly in young and previously unexposed horses. Dr. Lascola is currently participating in ongoing research with the goal of developing an intranasal strangles vaccine that is safer to use than those currently available.

The logistics of dealing with a strangles outbreak within a horse population can be overwhelming, but it is imperative that a plan be developed to prevent the spread of the disease.

“When faced with an outbreak, owners should work closely with their veterinarian to establish appropriate barrier precautions and isolation of infected horses,” says Dr. Lascola. “Horse traffic on and off the property should be stopped until infection in all horses is resolved.”

Strict methods of disinfecting the facilities will need to be followed to prevent the spread of the disease from the isolation area. Because horses that have recovered may still be infectious, the veterinarian will develop a program of testing the horse, by culturing nasal swabs or washes, over several weeks to determine when a horse can be reintegrated into the herd.

If you have any questions about strangles or you think that your horse may be ill, please contact your local veterinarian.