What is Poll Evil?
While poll evil is a seriously painful condition, its name is a bit humorous. Before medications for infections and pain were discovered, being touched in the poll area would cause quite an unhappy response when this area was infected or injured. This response gave the impression of being evil dubbing the horse as being poll evil. If the condition is not treated right away, the main ligament may become infected, causing even worse pain. This can make your horse keep the head still and upright to prevent movement and the agony that goes with it. Although Brucella is bacteria that usually affects cattle, horses can pick up the bacteria by eating from areas infested with bacteria shed by infected cattle.
Poll evil is a condition that starts out as an inflammation of the bursa in the neck and progresses to a large abscess at the poll, on the top of the back of your horse’s head. The poll is the nape of the neck and it is a large nerve center in the horse so this inflammation or abscess in the poll can be a serious concern for any horse owner. Although it is under the large ligament in the neck, it is similar to the covering of the spinal cord and can affect your horse’s ability to be ridden without severe pain.
In fact, even wearing a halter or bridle can bring intense discomfort. This condition can be caused by infection or an injury such as a blow to the head or neck. This can become life threatening if the infection spreads into the ligament and bones, which is incredibly hard to treat with success. In fact, many horses with poll evil require months or even years of treatment.
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Symptoms of Poll Evil in Horses
The symptoms of poll evil are generally the same for all horses but can be more severe as the infection gets worse. Here are the most commonly reported symptoms of poll evil:
- Swelling on the top of the neck and back of head between the ears
- High body temperature
- Pain in neck and head
- Holding the neck still and straight upright
- Drainage from neck or head
- Pulls away when touched in the face, head, or neck area
- Refusal to wear halter or bridle
- Dizziness and staggering
- Traumatic (injury)
Causes of Poll Evil in Horses
There are several causes of poll evil such as injury, irritation of the skin, or puncture wound, but the most common cause is infection of any number of bacteria, including but not limited to:
- Actinomyces bovis
- Bacteroides fragilis
- Brucella abortus
- Corynebacterium spp.
- Escherichia coli
- Onchocerca cervicalis
- Pasteurella spp.
- Proteus mirabilis
- Staphylococcus aureus
- Staphylococcus epidermidis
- Streptococcus equi
- Streptococcus zooepidemicus
Diagnosis of Poll Evil in Horses
Diagnosing poll evil requires a visit to see an equine veterinarian as soon as possible. The veterinarian will ask for your horse’s history, which should include medical records and immunizations (if you have them), recent injury or illnesses, abnormal behavior or appetite, and symptoms you have seen, if any. It is important to also let the veterinarian know if you have given your horse any medication recently because it could mask some symptoms and interfere with diagnosis and treatment plan.
A comprehensive physical examination comes next, which will usually start with a detailed assessment of the skin and hair from head to tail, looking for any injuries, inflammation, redness, and lesions. Next, the veterinarian will likely ask you to lead your horse around in a circle and then in a straight line (walking, cantering, and trotting) to check the muscles and joints in motion. Palpation of the abdomen and neck will be performed and then the veterinarian will check your horse’s body temperature, pulse, respirations, blood pressure, reflexes, height, weight, and breath sounds.
Laboratory tests will be performed next, which will usually include a complete blood count (CBC), serum biochemistry profile, blood urea nitrogen (BUN), packed cell volume (PCV), glucose, insulin, neutrophils and fibrinogen levels, and total protein. Bacterial cultures are also important in finding the bacteria that caused the poll evil. Radiological procedures are done last, including radiographs (x-rays) of the neck and head, contrast x-rays, and ultrasonography to find the pockets of fluid (abscesses) and fistulas.
Treatment of Poll Evil in Horses
Treating your horse for poll evil depends on the cause, but the most common treatments are cleaning and draining, medication, surgical, and therapeutic.
Cleaning and Draining
The first thing the veterinarian will do is clean the wound carefully with astringent such as iodine, betadine, or dimethyl sulfoxide (DMSO). Any abscesses will be drained and cleaned thoroughly.
An aggressive antibiotic regimen usually includes oxytetracycline, rifampin, or chloramphenicol either intravenously (IV) or by mouth for the next several months. It usually takes several rounds of antibiotics to get rid of the bacteria completely.
In some cases, thorough debridement of infected tissue and some form of surgery to reconstruct the area will be used to close the wounds.
Aqua therapy, heat, or cold packs can all be helpful in this condition.
Recovery of Poll Evil in Horses
Be sure to adhere to your veterinarian’s instructions and return for a follow up appointment as recommended. Keep an eye on the area to make sure the infection does not return.