Jaw Swelling in Horses: Causes, Risk Factors & Treatment

Jaw Swelling
Anatomy
Causes
Diagnosis
Treatment
Prevention

Jaw swelling is a common concern in equine medicine. A horse presenting with a swollen jaw can indicate a range of underlying health issues, from mild to potentially life-threatening conditions.

Common causes of jaw swelling in horses include dental disease, traumatic injuries, infections, immune-mediated reactions, and tumors.

Determining the exact cause requires a detailed veterinary evaluation, including the horse’s medical history, a physical exam, and advanced diagnostic tests. Treatment varies based on the underlying condition.

Regular dental exams, veterinary check-ups, and vaccinations are critical for reducing the risk of this condition. Understanding the causes, symptoms, and treatments of jaw swelling enables horse owners and caretakers to provide timely and effective care, ensuring the long-term health and well-being of their horses.

Jaw Swelling in Horses

Jaw swelling in horses is a symptom of various underlying conditions, some of which are relatively benign while others may be more serious. Associated conditions include tooth root abscesses, equine herpesvirus, strangles infection, and tooth or jaw fractures.

The most obvious sign is a noticeable lump or swelling on one or both sides of the jaw. This swelling may be soft or hard to the touch and can vary in size.

Horses may show signs of discomfort when the swollen area is touched or pressed. They might flinch, pull away, or display other signs of pain, such as head shaking or avoidance behavior. Horses may also display general behavioral changes such as becoming irritable or less cooperative with bridling.

If the swelling is due to dental issues or an abscess, the horse may have difficulty chewing food, leading to slower eating, dropping feed, or even refusal to eat. Chronic dental conditions that interfere with eating can lead to weight loss over time.

Concurrent Symptoms

Depending on the root cause, horses with jaw swelling may exhibit several concurrent symptoms that vary in severity, including:

Quidding (dropping feed)
Appetite loss
Head shaking
Excessive salivation
Facial paralysis
Blood in saliva
Deviated jaw
Head trauma
Difficulty eating
Bad breath (halitosis)
Lethargy
Fever
Nasal discharge

If any of these signs are observed, it is important to consult a veterinarian promptly for accurate diagnosis and treatment. The underlying conditions can range from minor infections to more serious issues like tumors or significant dental disease.

Anatomy

To understand oral pathologies of horses, it’s helpful to have a basic knowledge of equine oral anatomy. The mouth is the entryway to the digestive system and is where the first steps of digestion are initiated.

Horses are monogastric herbivores and need to thoroughly masticate (chew) their feed to optimize digestion further down the gastrointestinal tract. In addition to breaking down fibrous plant material, chewing triggers salivation, which is involved in the initial breakdown of food. Saliva also helps neutralize stomach acid and lubricates feed prior to swallowing. ^[1]

The horse’s tooth anatomy includes the following: ^[2]

Twelve incisors
Four canines (not always present)
Twelve premolars
Twelve molars

Illustration: Dr. Ana Mesa, PhD

The horse’s jaw is composed of the maxilla (upper jaw) and the mandible (lower jaw). The two jaws are connected via the temporomandibular joint (TMJ). In horses, natural jaw posture is referred to as anisognathic, meaning the maxilla is approximately 20% wider than the mandible. ^[2]

In addition to the dental structures, jaw swelling may be related to physiological changes in the surrounding soft tissue.

Possible sources of soft tissue swelling near or around the jaws include: ^[7]

Mandibular lymph nodes: There are prominent lymph nodes behind the jaw. The lymphatic system is involved in draining fluids from the tissues back into the blood stream. Lymph nodes often swell during times of immune system activation, when inflammation leads to fluid buildup.
Guttural pouches: The throat (pharynx) and middle ear in most mammals are connected by a structure called the Eustachian tube. In horses, this structure has a large sac roughly midway along its length called the guttural pouch. Any dysfunction or infection of the middle ear or the guttural pouches can cause swelling in this area.
Salivary glands: The horse has three pairs of salivary glands, and the mandibular glands lie along the jaw at the rear of the mouth. Obstruction or disease in the salivary glands may lead to swelling in some cases.
Oral tissues: Uneven wear of teeth and foraging on hard materials or off the ground can lead to soft tissue injuries in the cheeks. In severe cases, this can cause facial swelling.
Facial tissues: Any blunt force trauma near the mouth or jaw can result in inflammation and swelling.

Causes of Jaw Swelling in Horses

Jaw swelling is associated with an array of conditions spanning from traumatic injury to lymph node infections. Swelling may occur in the bone or joint tissue or in surrounding structures, particularly the lymph nodes behind the jaws.

Infectious Causes of Jaw Swelling in Horses

A number of infections, both viral and bacterial, can cause severe jaw swelling in horses. These include:

Equine herpesvirus
Strangles
Tooth infections
Actinomycosis

Equine herpesvirus (EHV)

Equine herpesvirus (EHV) is a viral respiratory infection caused by two separate groups of viruses: EHV-1 and EHV-4. The virus is transmitted via direct contact with the nasal secretions of infected animals. ^[3]^[4]

Following exposure, symptoms of EHV occur within 24 hours to six days and can include: ^[3]^[4]

Swelling of lymph nodes under the jaw
Nasal discharge
Cough
Lethargy
Fever

There is no specific treatment for EHV infection. Affected horses require supportive care and the administration of NSAIDs to alleviate fever symptoms. Infected horses should be isolated and quarantined for a minimum of two weeks after symptoms end to prevent spread of disease. ^[3]^[4]

Strangles

Strangles, also known as equine distemper, is a highly infectious bacterial disease affecting the horse’s lymphoid tissue. Strangles is caused by the bacteria Streptococcus equi. Young horses are more likely to develop severe clinical symptoms, which include: ^[5]^[6]^[7]

Fever
Reduced thirst and appetite
Nasal discharge
Eye discharge

In cases of strangles, lymph node abscesses on the neck rupture and drain into the guttural pouches, resulting in profuse nasal discharge. Diagnosis is based on clinical signs, especially the presence of abscesses.

Once diagnosed, treatment options for strangles in horses include: ^[5]^[7]

Isolation
Antibiotic treatment
Surgical drainage of abscesses
Supportive care
NSAIDs

Strangles can lead to severe complications, such as guttural pouch empyema (pus collection), and occasionally more severe conditions such as ‘bastard strangles’, where abscesses spread to other parts of the body. Due to the potential complications and the highly infectious nature of the condition, prevention is paramount. ^[5]^[7]

Prevention strategies include: ^[5]^[7]

Vaccination
General hygiene measures
Regular and proper disinfection of equipment
Quarantine of new horses or those returning from travel

Actinomycosis

Actinomycosis, commonly referred to as lumpy jaw, is an infection caused by bacteria of the Actinomyces genus. Different species of bacteria belonging to the genus cause disease in various animal species. Horses are mainly infected by A. denticolens. Affected horses present swollen lymph nodes. ^[8]^[9]

Actinomyces bacteria are part of the horse’s healthy oral bacterial flora. Actinomycosis arises when the bacteria proliferate in the oral soft tissue via small wounds. Affected horses can develop facial distortions and loose teeth. ^[8]^[9]

Prognosis varies and depends on the severity and location of infection. Long-term infection of the bone carries a poor prognosis. ^[8]^[9]

Tooth Root Abscess

Tooth root abscesses are an avoidable, but common, dental issue in horses. Abscesses occur as the result of dental fractures or the presence of gaps between teeth, both of which can cause the accumulation of feed debris. Horses with tooth root abscesses may exhibit symptoms including: ^[10]

Warm, painful swelling on the jaw
Appetite loss
Weight loss
Difficulty eating
Colic
Excessive salivation
Halitosis (bad breath)

Treatment options for dental abscesses commonly include: ^[10]

Extraction of affected teeth
Administration of antibiotics
Anti-inflammatory medications

Traumatic Causes of Jaw Swelling in Horses

Sometimes jaw swelling in horses is related to direct trauma to the jawbone or temporomandibular joint (TMJ), which connects the jawbone to the skull. Injuries to the jaw and surrounding structures of the mouth can result in swelling.

Jaw Fractures

Jaw fractures are relatively common in horses. Trauma to the head and face can occur as a result of collisions, falls, kicks, and other blunt trauma.

The main symptoms of jaw fractures in horses include: ^[11]^[12]

Swelling of the face
Excessive salivation
Difficulty eating
Signs of discomfort

Diagnosis is straightforward; in severe cases, the diagnosis is self-evident. In others, X-rays and other diagnostic imaging may be required. Simple fractures often do not require any treatment, as they heal on their own. Severe cases require medical treatment and surgery.

Surgical options include: ^[11]^[12]^[13]

Intra-oral wiring: Used to treat fractures located in front of the cheek teeth. The procedure involves insertion of a stainless-steel wire around the teeth on each side of the fracture to anchor the two parts of the bone.
Bone plating: In severe cases where wiring may not suffice, screws and plates may be used alongside the wire to further stabilize the jaw.
External fixation: An advanced surgical procedure used in cases that require additional stabilization.

In the majority of cases, the outcome of mandibular surgery is excellent, but infections can occur. Horses recovering from mandibular surgery require hospitalization to receive fluid therapy and nutritional support. ^[11]^[12]^[13]^[14]

While antibiotics and pain medication are usually sufficient, in the case of infections, additional antibiotic treatment is required. ^[11]^[12]^[13]^[14]

Teeth Fractures

Fractures are a common finding in equine dental practice. There are multiple possible causes of teeth fractures including:

Uneven wear
Chewing stones
Injuries

Fractured teeth can cause significant discomfort and complications. If the fractured teeth fill with feedstuff, they can rot, leading to: ^[15]

Infection
Facial swelling
Oral pain
Decreased appetite
Quidding

On occasion, the issue may resolve on its own through the spontaneous loss of displaced fragments. However, surgical removal of the fractured tooth may be necessary. ^[15]

Other Causes of Jaw Swelling in Horses

Equine jaw swelling is sometimes related to systemic physiological causes, including conditions such as grass mumps, tumors, and sialoliths, which can all contribute to abnormal growths or obstructions around the jaw.

Grass Mumps

Another cause of facial swelling in horses is enlargement of the parotid salivary glands due to an allergic reaction to pollens in pastures.

Commonly referred to as “grass glands” or “grass mumps,” this condition is not well understood at this time. While usually not painful, the swelling can obstruct range of motion in the face and neck, which is irritating to the horse. ^[16]

Tumors

Fortunately, tumors in horses are relatively rare compared to other species, affecting only 2-3% of all equines. These growths can originate from various tissues, including the skin, teeth, or bone. ^[17]^[18]

The most common type of equine tumors are sarcoids, which frequently affect the head and neck. Treatment of sarcoids in horses varies depending on the location and stage of the tumor. Options include surgical removal, laser therapy, and immunotherapy. ^[17]^[18]

Odontogenic tumors develop following dental issues. They include ameloblastomas, ameloblastic odontomas, and complex odontomas. These kinds of tumors can affect both the horse’s maxilla and mandible. Treatment involves the surgical removal of the mass. ^[17]^[18]

Bony tumors include osteomas, osteosarcomas, and ossifying fibromas and most commonly affect the mandible. Treatment requires surgical excision and radiation therapy. ^[17]^[18]

Tumors of the guttural pouch are extremely rare. Treatment options are often unsuccessful, and affected horses carry a very poor prognosis. ^[17]^[18]

Sialoliths

Sialolithiasis is a condition that causes the formation of calcified masses in the horse’s salivary glands. These masses typically form as a consequence of the progressive layering of calcium around small fragments of plant material that penetrate the salivary ducts. ^[19]^[20]

As the masses grow, these “stones” can cause inflammation, infections, and swelling. Due to the blockage, salivation decreases and digestives complications often ensue. ^[19]^[20]

Because sialolithiasis has a slow progression, affected horses do not present symptoms for a long time. There have been reports of some animals presenting initials symptoms several years after the initial formation of the salivary stone. ^[19]^[20]

The main symptom of sialolithiasis in horses is facial swelling. Other clinical signs can include: ^[19]^[20]

Quidding
Decreased appetite
Weight loss
Halitosis (bad breath)
Fever
Difficulty swallowing

Fortunately, sialolithiasis is easily treated and carries an excellent prognosis following surgical removal of the stone. ^[19]^[20]

Diagnosis

Diagnosing the underlying cause of jaw swelling in horses requires a comprehensive approach due to the variety of potential underlying issues. The first steps are a physical examination and medical history conducted by your veterinarian. ^[7]

Based on these findings, your veterinarian will run specific tests such as diagnostic imaging, blood tests, and biopsies to precisely identify the cause and determine the appropriate treatment plan.

Treatment

The management and treatment of jaw swelling in horses vary depending on the underlying condition. Treatment may include: ^[7]

Antibiotic therapy
Supportive care including NSAIDs, fluid therapy, and rest
Surgical drainage
Surgical removal of tumors, bone fragments, calcified masses, or any other foreign material
Stabilization techniques such as wiring, plating, or screwing
Quarantine and isolation measures
Nutritional support

Prevention

Regular dental check-ups and routine veterinary care are key in the prevention of odontogenic issues, which are common causes of jaw swelling in horses.

Vaccinations for diseases like strangles and equine herpesvirus (EHV) play a vital role in preventing infectious diseases that may cause swelling and other severe symptoms.

Maintaining good hygiene practices and robust disinfection of equipment reduce the risk of infections and ensure a clean environment for livestock. This, coupled with the implementation of quarantine protocols for new or returning horses, helps prevent the introduction and spread of infectious diseases within the farm.

Prompt veterinary intervention for oral injuries and infections is also necessary to prevent complications.

By adhering to these preventive strategies, horse owners and caretakers can significantly reduce the likelihood of their horses developing jaw swelling and ensure the overall health and well-being of their herd.

Summary

Swollen jaws are a common finding in equine medicine. Causes may be related to the jaw bones and joint itself, dental problems, or systemic disease.

Common causes of jaw swelling in horses include viral and bacterial infections, teeth fractures, allergies, and traumatic injury to the jaw.
Many forms of jaw swelling are easily treated and carry a positive prognosis.
Staying up to date with routine dental and veterinary care are the best strategies to detect oral health problems early.