Strangles
Strangles is caused by Streptococcus equi, a gram positive bacterium known for its strength and persistence. S. equi can live in the environment, in the nasal discharge of infected horses, and in the guttural pouches of carrier horses. Transmission occurs when there is direct or indirect transfer of bacteria within nasal discharge between affected and susceptible horses. Direct transmission refers to horse-to-horse contact through mutual head contact. Indirect transmission occurs through the sharing of contaminated housing, water sources, feed utensils, tack, and other less obvious fomites such as people. The bacteria enter via the nasal passages and slowly make their way to the lymph nodes in the lower jaw or throat-latch area. Diagnosis consists of a nasal wash that targets these areas. Horses usually develop signs of strangles several days to a month after exposure. They usually present with a fever (temperature over 101.5 degrees Fahrenheit), lethargy, and anorexia, followed 2 to 3 days later by swollen lymph nodes. Horses with swollen lymph nodes in the throat-latch area can struggle to breath if the swelling gets large enough to compress their trachea (windpipe) that runs in that area. If this happens, the horse can suffocate to death if emergency treatment is not given. Emergency treatment consists of performing a tracheotomy, which means making a breathing hole in the horse’s neck and bypassing the compression on the trachea. If the swollen lymph nodes have a soft spot, they may need to be opened, flushed, and cleaned in the field or under general anesthesia.
As an owner, prevention and early detection are keys to fighting this disease. When traveling to horse shows, make sure that your horse is housed near other healthy horses. If you notice the horse in the stall next door has a nasal discharge, please ask your horse to be moved. When bringing a new horse into the barn, isolate him or her for 3 weeks to prevent the transmission of disease. There are two types of Strangles vaccines on the market (one is given intramuscularly and the other is given intranasally), but there are possible complications. Safety issues include residual virulence with subsequent abscess development, nasal discharge, and rarely, immune-mediated vasculitis (also known as purpura hemorrhagica), which is life-threatening. The vaccine should not be given if the horse has signs of strangles or has been exposed to strangles in the past year. Because the vaccine contains live S. Equi, it should not be given at the same time as other injections to prevent the development of abscess formation at the other injection sites. During an outbreak, only horses with no known contact with strangles cases or the exudates should be vaccinated. However, know that immunity takes about 2 weeks to develop, so vaccination will not prevent a horse from developing strangles if exposed in that time frame. Monitor rectal temperatures on a daily basis in the event of an outbreak. S. equi is normally not present on the mucosa until 24 to 48 hours after the onset of fever; therefore, horses monitored with daily rectal temperatures during an outbreak may be recognized early and isolated to limit transmission.
Strangles is a serious disease that often presents in barns that have horses coming and going. If your horse stops eating or acts tired, please monitor his or her temperature and call your veterinarian if the temperature is over 101.5 degrees Fahrenheit. If your horse develops a swelling in the lower jaw or throat-latch area or has trouble breathing, please call your veterinarian. The sooner you catch Strangles, the better.
If you have any questions or concerns feel free to contact us at
802-893-6800 or email me at jwilkinson@vlac.net
Jenny Wilkinson,DVM – Vermont Large Animal Clinic
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