Vaccination and Biosecurity for Strangles Prevention

Show season is in full swing and many owners are traveling with their horses to events across the country. Keeping horses healthy when traveling can present challenges. Increased travel can increase potential exposure to risk-based infectious diseases. Pfizer Animal Health advises that proper vaccination by a veterinarian is the best way to help protect horses against strangles and other contagious diseases.

According to the American Association of Equine Practitioners, the incidence of strangles varies regionally, as well as from farm-to-farm. Therefore, it is listed in their guidelines as a 'risk-based' disease. Risk-based vaccinations differ from core vaccinations in that they help protect from diseases that are endemic to a region, those with potential public health significance, and required by law. Core diseases include Eastern equine encephalitis, Western equine encephalitis, rabies, and tetanus. Due to these variations, it is important to consult a veterinarian when developing a vaccination program.

"Strangles is considered a risk-based disease, meaning it is at the discretion of the veterinarian and the horse owner whether to vaccinate," said Tom Lenz, DVM, MS, Dipl. ACT, senior director of equine veterinary services for Pfizer Animal Health. "However, a disease outbreak can happen anytime, anywhere and so it's a good idea to help maximize the protection of our horses through proper vaccination."

Strangles, caused by the bacterium Streptococcus equi, is a highly contagious disease that localizes in a horse's lymph nodes in its upper respiratory tract. Strangles can affect horses of any age, but most commonly infects those between weaning and five years of age. The disease is usually acquired after exposure to another horse that is shedding the S. equi bacteria, either during or after its own bout of the illness. Once a horse is exposed to the bacteria, it can begin to show clinical signs (e.g., high fever, poor appetite, and depression) in two to six days. Horses will usually excrete a thin, watery discharge from their nostrils, which will quickly turn thick and yellow. The horse's upper respiratory lymph nodes can become enlarged and might abscess, most noticeably the ones at the throat latch area and between the jawbones. Most horses will recover, but approximately 10% of untreated horses could die, usually from pneumonia, a secondary infection. Infectious horses can spread the bacteria even when they are no longer showing signs of the disease. Around 20% of horses remain contagious for four to six weeks after all clinical signs vanish.

"Strangles is highly contagious," said Lenz. "Therefore, owners and caregivers should follow proper biosecurity practices to try to help prevent contamination of equipment and the spread to other horses."

Vaccination can be used as an aid in the prevention of strangles. Although vaccinated horses might still contract the disease, they tend to experience a less severe illness. Horses cannot contract strangles from the vaccine itself.

If you suspect that a horse has strangles, notify a veterinarian to confirm the disease. The sooner the positive diagnosis is reached, the sooner the horse can be isolated and treated.

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