Disorders of the Foot in Horses

Bone Cyst in the Pedal Bone

A large cyst in the pedal bone (the distal phalanx) can cause longterm lameness that may be severe and unresponsive to anti-inflammatory medication. This uncommon condition, caused by trauma, may be seen in any foot but more often affects a hindfoot. The diagnosis may be confirmed by your veterinarian through the use of regional analgesia and x-rays. Progressive weakening of the pedal bone can lead to a secondary fracture. Because of the cyst's location and size, surgery is not always successful. However, some horses do return to performance status, while others may be used for less strenuous activity such as breeding.

Bruised Sole and Corns

Bruising on the sole of the foot usually is caused by direct injury from stones, irregular ground, or other trauma. Poor shoeing, especially in horses with flat feet or dropped soles, can increase the risk of bruising, usually around the outside edge of the sole. Bruising may or may not be associated with lameness, but if it becomes longterm, the affected area can become infected.

A corn is a type of bruise that appears in the sole at the buttress (that is, the angle between the wall and the bar). It is most common in the forefeet on the inner buttress. Corns may arise from pressure applied to the sole by the heel of a shoe improperly placed or left on too long. Shoes that have been fitted too closely at the quarters can also cause corns. Malformations of the feet, such as straight walls that tend to turn in at the quarters, increase a horse's vulnerability. Other causes include excess trimming of the sole (which exposes the sensitive tissue to injury) or neglect of the feet to the extent that they become long and irregular.

Corns may be dry, with only mild inflammation, or moist, with extensive inflammation. If infection sets in, they may discharge pus. The sole of the foot looks discolored, either red or reddish yellow, and lameness sometimes occurs in the supporting leg. Applying pressure may cause discomfort or pain. If not promptly treated, a corn may lead to the formation of a pus-filled tract that runs to where the horn of the hoof meets the skin (the coronet).

The outlook for recovery is favorable. In uncomplicated dry corns, the first step is to relieve pressure on the affected area. Shortening a too-long toe or using an appropriate type of bar shoe (such as a three-quarter-bar shoe) can relieve pressure. A corn that produces pus must be surgically drained, then bandaged to allow continued drainage. Hot foot baths and poultices may help, and the horse should be kept in a dry, clean box stall. After the infection is controlled, the cavity can be packed with sterile gauze and topical antibiotic ointment. A metal, rubber, or leather sole may be placed between the shoe and the foot.

Canker

Canker is an enlargement of the horn-producing tissues of the foot, involving the tough flexible pad in the middle of the sole (the frog) and the sole, with obvious production of pus. The cause is unknown. Primarily a disease of heavy draft horses, canker is seldom seen today, although it has been seen in certain stables of light horses in the southern United States.

Canker is most often found in the hindfeet and is frequently well advanced before detection. The frog may appear to be intact but has a ragged, oiled appearance. The horn tissue of the frog loosens easily and reveals a swollen, foul-smelling layer covered with dry, diseased, dead tissue. The disease may extend to the sole and even to the wall of the hoof and show no tendency to heal.

The outlook for recovery for canker is guarded. Treatment must be intensive. All loose horn and affected tissue should be removed, and an antiseptic or antibiotic dressing applied daily. A clean, dry wound environment must be maintained to allow healing, which may take weeks or months. If the horse is not lame, it may be able to return to work during the healing period by use of a special shoe to maintain the dressing.

Contracted Heels

Contracted heels are seen primarily in the forefeet of light horses. The condition may be caused by improper shoeing that draws in the quarters. This prevents hoof expansion and adequate frog pressure. Dry hooves, excess scraping of the wall, and trimming of the bars make a horse more prone to contracted heels. However, this condition may also occur after the use of a hoof-immobilizing shoe, such as that used for fracture of the third phalanx (pedal bone).

When the heel is contracted, the frog is narrow and shrunken, and the bars may be curved or almost parallel to each other. The quarters and heels are noticeably contracted and drawn in. The hoof horn is dry and hard, and heat may be noticed around the heels and quarters. If the horse is worked at speed, it may become lame, and its stride length will be shortened.

The outlook for recovery is guarded. In advanced cases, recovery can take 6 to 12 months. The most important factors in treatment are to moisturize the hooves and to promote expansion. This can be achieved by soaking the feet in water daily for 10 to 14 days followed by corrective shoeing. Hoof-moisturizing products that contain oils or waxy substances should be used with caution because they can keep water out of the hoof. Slipper shoes with no more than 3 nails in each branch promote hoof expansion. Quarter clips and the fourth shoe nail must be avoided.

A veterinarian can thin the wall of the quarters or groove the walls parallel to the coronet to aid in expanding the heels. As the quarters grow out, the procedure may need to be repeated until the heels and quarters are expanded normally.

Fracture of the Navicular Bone

The navicular bone may fracture as a result of trauma or a jarring injury to the foot. It may also break as a consequence of navicular disease (see Bone, Joint, and Muscle Disorders in Horses: Navicular Disease). Fracture of the navicular bone is much less common than that of the pedal bone, but it may be seen in either the fore- or hindfeet. Pain may vary, but a hoof tester usually can locate the general area of the fracture. Lameness is persistent. X-rays and regional analgesia can confirm the diagnosis.

Treatment is prolonged rest and corrective trimming, although the fracture seldom heals entirely. Surgical repair using lag screws is an option, but the outlook for recovery remains guarded to poor.

Fracture of the Pedal Bone

Pedal bone fractures (fracture of the third phalanx, os pedis, or distal phalanx) generally follow a jarring injury, producing a sudden onset of lameness during exercise or racing. Most fractures are through the wing (flat side) of the pedal bone and often extend up into the adjacent joint.

A horse that fractures its pedal bone immediately becomes lame. Compressing the foot with hoof testers causes pain. Lightly tapping the hoof with a hammer also may cause pain, and turning the horse or making it pivot on the affected leg worsens the lameness. Lameness may improve considerably after 48 hours of stall rest, unless the fracture extends into the joint.

Diagnosis is confirmed by regional analgesia and x-rays. X-ray confirmation may be difficult immediately after the injury because the fracture may be only a hairline at this stage. Repeating the x-ray 2 or 3 days later may be necessary for confirmation and to determine the extent of the fracture.

Conservative treatment of 6 to 9 months' rest is usually all that is required for fractures that do not involve the joint. The horse should return to soundness, although the fracture will remain visible on x-rays. It is usual to fit a plain bar shoe with a clip well back on each quarter to limit expansion and contraction of the heels. In young horses (less than 3 years old), fractures into the joint usually heal satisfactorily, provided a 12-month rest period is given. Horses older than 3 years have a much less favorable outlook for recovery, and insertion of a bone screw is recommended. However, infection is a frequent complication. Many fractures heal in the presence of infection, but the screw must be removed at a second surgery to restore the horse to complete working soundness.

Keratoma

A keratoma is a hard, thickened area of the horn, usually at the toe. It is believed to follow longterm inflammation caused by nail bind, which occurs when a horseshoe nail is driven close to, but not into, the soft tissue. A keratoma may also be caused by mechanical injury to the wall or coronet, or by hoof-grooving. The condition may be difficult to detect until the growth is well advanced. Examining the surface of the underside of the horse's forefoot shows that the growth has pushed the white line in toward the center of the sole. In severe cases, the pressure shrinks the pedal bone. Surgical removal of the mass is recommended. In mild cases, corrective shoeing may give some temporary relief. The outlook for recovery is guarded.

Laminitis (Founder)

A horse's foot has 2 types of laminae (tissue layers). The sensitive laminae are attached to the pedal bone. The insensitive laminae are the layers of tissue just inside the hard exterior of the hoof. The word laminitis means “inflammation of the laminae,” and it can refer to either a short-term (acute) inflammation or the disease caused by longterm or repeated (chronic) attacks of inflammation. Laminitis can develop in the forefeet, in all 4 feet, or in the hindfeet only. Biomechanical laminitis can be seen in a single foot, usually as a complication of a severe lameness or bone injury in the limb on the opposite side of the body.

Acute laminitis occurs when an inadequate supply of blood reaches the laminae. The reduced blood flow causes tissue to break down where the sensitive and insensitive laminae come together, eventually leading to a degeneration of the union between the layers of tissue. When treatment is unsuccessful, the pedal bone often rotates. If rotation progresses, a hole may form through the sole of the foot.

The most common causes of laminitis are ingestion of too much grain, grazing of lush pastures (especially in ponies), and excessive exercise or repetitive trauma. Other causes include generalized infections, colic, and treatment with corticosteroids and certain other medications. The risk is higher in ponies and in horses that are overweight and unfit. The number of cases of acute laminitis tends to increase whenever there is a flush of new grass.

Initially, the disturbances in the circulation to the foot are reversible. However, if the condition is severe or lasts for a long time, the outlook for recovery is poor. The pedal bone may rotate, or the hoof may alter its shape or separate from the underlying tissues. These changes may be irreversible, and secondary infection is common.

Signs and Diagnosis

In acute laminitis, the horse is depressed, has no appetite, and stands reluctantly. The horse resists exercise and attempts to shift weight off of the affected feet. If forced to walk, it has a slow, crouching, short-striding gait. Each foot, once lifted, is set down as quickly as possible.

Usually, heat is apparent in the whole hoof, especially near the coronary band. Pain can cause muscle trembling, and pressure reveals tenderness in the feet. If an effective treatment is not given quickly, the pedal bone may rotate. X-ray evidence of rotation can be present as early as the third day. Horses with laminitis typically have elevated vital signs, such as increased body temperature, heart rate, and respiration. In exceptionally severe cases, for which the outlook for recovery is unfavorable, a blood-stained discharge may seep from the coronary bands.

In less severe cases, the horse may exhibit any or all of the above signs but to a lesser degree. Often, there is only a mild change in stance, with reluctance to walk and some increased sensitivity in the soles of the affected feet. Episodes of acute laminitis tend to come back at varying intervals and may develop into a chronic condition.

Chronic laminitis is characterized by changes in the shape of the hoof and usually follows one or more acute attacks. Bands of irregular horn growth may appear in the hoof, and the hoof itself may narrow and become elongated, with the wall almost vertical at the heel and horizontal at the toe. As the condition progresses, the sole thickens and either flattens or begins to curve outward. When standing, the horse continually shifts its body weight from one foot to the other. X‑rays reveal rotation of the pedal bone, as well as a diseased state in which the bone has become very porous. The top of the bone is forced downward and presses on the sole. In severe cases, it may poke through the sole just in front of the point of the frog.

To diagnose laminitis, a medical history is taken, noting possible contributing factors such as a grain overload in the diet. The physical examination will pay close attention to the posture of the horse, any abnormalities of the hooves, and a reluctance to move. Mild cases with no visible hoof deformity can be identified by x‑rays of the affected feet.

Treatment and Outlook

Acute laminitis is considered a medical emergency because pedal rotation can occur quickly. If laminitis is suspected, your veterinarian should be contacted immediately.

In cases of grain overload, it is critical to prevent the absorption of toxic material from the gastrointestinal tract. Mineral oil is usually recommended—1 gallon (4 liters), by mouth. Purgation should not be performed on horses in the acute phase as they tend to be dehydrated.

Traditionally, cold packs or ice packs applied to the affected feet have been encouraged, but recent evidence suggests that hot packs used early in the course of the disease may be more beneficial.

Your veterinarian may prescribe certain nonsteroidal anti-inflammatory medications to lessen inflammation. Administration of corticosteroids is not recommended. Follow prescriptions exactly as described.

Heart-bar shoes have been used in acute cases of laminitis in an attempt to distribute sole pressure and avoid pedal rotation. Because an improperly fitted heart-bar shoe aggravates the pain, correct fitting is essential.

Treatments of chronic laminitis have attempted to restore the normal alignment of the rotated coffin bone and encourage frog pressure by lowering the heels, removing excess toe, and protecting the dropped sole. This requires corrective hoof trimming and the use of full leather pads or a heart-bar shoe. The hoof should be trimmed and the shoe reset at 4- to 6‑week intervals. This approach can be successful in selected cases but is expensive, labor intensive, and prolonged.

Surgical removal of the separated hoof wall may also be recommended and has been used in cases of both acute and chronic laminitis. This procedure carries risk and should follow consultation between the veterinarian and the person who makes and fits the horseshoes (farrier).

Despite prompt treatment, the outlook for recovery is guarded until recovery is complete and it is evident that the hoof structure is not altered.

Navicular Disease

Navicular disease is essentially a longterm, degenerative condition of the navicular bursa and navicular bone that involves damage to the surface of the bone and the flexor tendon with abnormal outgrowth of bone on the borders of the bone. Thus, it is a syndrome with a complex disease development. It is one of the most common causes of longterm forelimb lameness in horses. Navicular disease is essentially unknown in ponies and donkeys.

The exact cause is unknown, but many factors involving the navicular bone and its blood supply, as well as the nearby ligament, joint, bursa, and tendon, may contribute. It is most often a disease of the more mature riding horse, although it has been seen in 3-year-olds. Navicular disease may be partially hereditary. Defective shoeing that stops the action of the frog and the quarters may also be a contributing factor, as well as trauma or a jarring injury.

Usually, navicular disease is slowly and subtly harmful in onset. An early sign may be the way in which the horse relieves pressure on the painful area by pointing or advancing the affected foot with the heel off the ground. If both forefeet are affected, the horse points them alternately. Lameness tends to come and go early in the course of the disease. The stride is shortened, and the horse may tend to stumble. Turning the horse in a tight circle usually produces a short-term worsening of lameness. There may be soreness in the shoulder muscles after the changes in posture and gait, resulting in a common complaint of “shoulder lameness.”

Diagnosis is based on a complete history and careful physical examination. The lameness can be eliminated by the use of regional analgesia (see Bone, Joint, and Muscle Disorders in Horses: Regional Analgesia). X‑rays show degenerative changes involving the navicular bone, including some abnormal outgrowths of bone and bone reshaping.

Because the condition is both longterm and degenerative, it can be managed in some horses but not cured. With severe lameness, rest is recommended. Foot care includes trimming and shoeing that restores normal bone alignment and balance. Nonsteroidal anti-inflammatory drugs, along with proper foot management, extend serviceable soundness in some horses. The injection of corticosteroids into the bursa may relieve pain but is not curative.

Surgical removal of part of the palmar digital nerve (“denerving”) may provide relief from pain and prolong the usefulness of the horse, but this should not be considered curative. The surgical removal of nerves can be accompanied by severe complications such as a painful tumor formation.

The outlook for recovery is guarded to poor, but a carefully designed treatment plan can prolong the usefulness of most horses. Athletes may even temporarily return to competitive status. However, over months or years, all affected horses eventually stop responding to treatment.

Pedal Osteitis

Pedal osteitis is an inflammation of the sensitive structures of the soles of the forefeet, associated with inflammation of bony tissue and mineral loss from the coffin bone. Repeated jarring injuries, laminitis (see Bone, Joint, and Muscle Disorders in Horses: Laminitis (Founder)), persistent corns, and chronic bruised soles have been implicated as causes. Pedal osteitis is common in performance horses and usually is associated with work on hard tracks.

Lameness may not be obvious because usually both forelimbs are affected. There may be a stilted or shuffling action in front, with signs of discomfort in the hoof region. Tapping and pressure from hoof testers usually reveal tenderness over the entire sole. X-rays are helpful in diagnosis and can be used to help differentiate this condition from others with similar signs.

Treatment involves prolonged rest, anti-inflammatory medication, and careful shoeing to relieve sole pressure. The outlook for recovery is guarded, but the serviceable soundness of many horses can be extended by proper management.

Puncture Wounds of the Foot

Puncture wounds are usually the result of poor horse-shoeing technique but can occur when a horse steps on a penetrating foreign object. Nail bind implies that a nail has been driven close to the sensitive structures of the foot, causing severe pain and lameness. Nail prick means that the thick, sensitive layer of connective tissue beneath the outer layer of skin has been pierced.

When a foreign object penetrates the sole of the foot, it can introduce microorganisms that can cause infection. Lameness is usually severe following a puncture wound, especially when the foot bears weight; the degree of lameness may be similar to that produced by a fracture. The horse may stand and point the affected foot. The foot will show increased pain and may be warm to the touch. Infection may progress to the coronary band, and abscesses may form. Subsequently, the pastern and fetlock areas accumulate fluid and swell. Diagnosis requires confirming the site of pain by pulling the shoe, applying hoof testers, and paring down the suspect area to locate the foreign object or its path of entry.

Prompt treatment with disinfectants and poultices is important for nail bind and nail prick. Ensuring adequate wound drainage helps prevent the formation of abscesses. In pricked foot, the outlook for recovery is good, provided diagnosis is made and treatment begun early. If an abscess has developed below the sole of the foot, treatment may be prolonged, and the outlook for recovery is guarded. If infection spreads to the joints, the outlook for recovery is unfavorable.

Any foreign object must always be found and removed, and the infected area pared with a hoof knife to allow adequate drainage. The foot should then be kept in a rubber or plastic boot for 3 to 5 days with a cotton pad soaked in saturated magnesium sulfate solution or other suitable poultice. All horses with puncture wounds should be immunized against tetanus. If the pain is severe, regional analgesia provides temporary relief. Antibiotic treatment is not necessary, provided the infection is localized and good drainage has been achieved. Deep punctures of the foot that involve the deep digital flexor tendon, navicular bursa, navicular bone, or third phalanx require emergency surgery.

Pyramidal Disease (Buttress Foot)

Pyramidal disease, also called buttress foot, involves inflammation of the covering of connective tissue that surrounds the coffin bone. The disease may arise after trauma or from a separating fracture caused by excess tension on the tendon. Secondary arthritis is a likely complication. In early stages, the area will be hot and painful. The toe region above the coronet usually enlarges, creating the “buttress foot” appearance.

There is no specific treatment for pyramidal disease. Anti-inflammatory medication given by mouth or injection may be beneficial. Corrective shoeing can help minimize lameness. Surgery has been successful for the separating fractures. The outlook is guarded to poor for a return to soundness.

Quittor

Quittor is a chronic inflammation of the cartilage of the pedal bone characterized by death of the cartilage and one or more sinus tracts extending from the diseased cartilage through the skin. It is seldom encountered today but once was common in working draft horses.

In most cases, injury to the coronet or pastern introduces infection into the deep tissues, forming a pus-filled sore called an abscess. Quittor may also occur after a penetrating wound through the sole. The first sign is an inflammatory swelling over the cartilage, followed by the formation of abscesses. During the inflammatory stage, lameness occurs.

Surgery to remove the diseased tissue and cartilage is usually successful. Drug treatment without surgery is likely to fail. Without treatment and drainage the cartilage will die, and abscesses will recur and extend to deep structures, leading to longterm lameness. If damage is extensive and the distal phalangeal joint has been invaded, the outlook for recovery is unfavorable.

Sandcrack (Toe Crack, Quarter Crack, Heel Crack)

In sandcrack, cracks in the wall of the hoof begin at the coronet and run down the hoof. They are most common in racehorses. Excess drying of the hoof makes the hoof more prone to cracking, but trauma or structural factors are usually to blame. Extensive injury to the coronet may leave a crack in the wall characterized by an overlapping buildup in the wall at the site of injury. This latter condition is referred to as false quarter.

A crack in the horn coming from the coronet is the most obvious sign of sandcrack. Lameness varies depending on the site and extent of the injury; if infection is involved, lameness may be accompanied by a bloody or pus-filled discharge and signs of inflammation.

Treatment involves surgery and corrective shoeing to change the distribution of weight on the hoof. The use of bar shoes is often recommended. If the crack has become infected, an antiseptic pack may be used. The hoof is then bandaged until new horn formation is evident.

Scratches (Greasy Heel)

Scratches, sometimes referred to as greasy heel, is a longterm inflammation of the skin in which the rear surface of the pastern and fetlock enlarge and ooze discharge. It often is associated with poor stable hygiene, but no specific cause is known. Heavy horses are particularly susceptible, and the hindlimbs more commonly are affected. Standardbreds often are affected in the spring when tracks are wet. The common use of limestone on racetracks has been associated with scratches.

Scratches may go unnoticed if hidden by the “feather” at the back of the pastern. The skin is itchy, sensitive, and swollen during the early stages; later, it thickens and loses all but its shorter hairs, which stand in an upright position. The surface of the skin is soft, and the grayish discharge has a rotten odor. If the condition becomes chronic, small masses of tissue may appear. Lameness may or may not be present, but it can be severe if inflamed tissues beneath the skin of the limb become infected. As the condition progresses, the skin of the affected regions thickens and hardens.

Persistent and aggressive treatment is usually successful. This consists of removing the hair, regular washing and cleansing with warm water and soap to remove all soft discharge, drying, and applying an astringent dressing. If small masses appear, a veterinarian should remove them. Infection requires whole-body antibiotics and preventive treatment for tetanus.

Seedy Toe (Hollow Wall)

Seedy toe is a condition of the hoof wall in the toe region, characterized by changes in or loss of the tissue that makes up the horn. It is most often a consequence of mild, longterm laminitis (see Bone, Joint, and Muscle Disorders in Horses: Laminitis (Founder)). The outer surface of the wall appears sound, but the inner surface of the wall is mealy, and there may be a cavity due to loss of horn substance. Tapping on the outside of the wall at the toe produces a hollow sound over the affected portion. The disease may affect only a small area or nearly the entire width of the wall at the toe. Lameness is infrequent but may occur if infection or an abscess is also present.

The outlook for recovery is usually good. The diseased portion of the hoof wall should be cleaned and packed with juniper tar and oakum. In the absence of lameness, shoeing and work can continue. If the condition is extensive, the outer wall may need to be removed over the affected area.

Sheared Heels

In sheared heels, unevenness of the heels produces a severe imbalance of the foot. This results in one side of the heel contacting the ground before the other, creating a shearing force at the rounded parts of the heel, uneven growth of the toe, and severe overriding contraction of the heels. The heel develops longterm soreness similar to that of navicular disease (see Bone, Joint, and Muscle Disorders in Horses: Navicular Disease). Hoof cracks, deep cracks between the rounded parts of the heel, and an infection of the frog frequently accompany the problem. Navicular disease may occur at the same time.

Heel alignment and foot balance may be restored with corrective trimming and shoeing. A full bar shoe with a reinforcing diagonal bar to support the affected quarter and heel is used. Improvement will likely require several shoe resettings. The outlook for recovery is good in uncomplicated cases, if corrective measures are consistently applied until new hoof growth occurs.

Sidebone

Sidebone is the hardening (calcification) of the cartilage of the coffin or pedal bone. It is most common in the forefeet of heavy horses working on hard surfaces. It also is frequent in hunters and jumpers but is rare in racing Thoroughbreds. Repeated jarring injuries to the quarters of the feet are probably the most basic cause. Improper shoeing that stops normal movement of the quarters may also lead to sidebone. Other cases arise from direct trauma.

The hardened cartilage may stick out above the coronet. The presence of lameness depends on the stage of the hardening process, the amount of jarring injury sustained by the feet, and the type of terrain underfoot. Often, no lameness is noted. A narrow or contracted foot makes lameness more likely. Lameness also may occur if sidebone is accompanied by another condition such as navicular disease. The stride may be shortened, and walking the horse across a slope may exaggerate the soreness.

Sidebone may be diagnosed using examination and palpation (hands-on evaluation of the leg); however, x-rays are necessary for confirmation. When lameness is present, corrective shoeing to promote expansion of the quarters and to protect the foot from jarring injury often helps. Grooving the hooves also may promote expansion of the wall.

Thrush

Thrush is a degeneration of the frog with secondary bacterial infection. It results from poor management and hygiene, such as allowing the horse to stand too long in wet conditions and failing to clean the hooves regularly. The condition is more common in the hindfeet. The affected area is moist and contains a black, thick discharge with a characteristic foul odor. These signs alone are sufficient to make the diagnosis.

Treatment should begin by providing dry, clean material underfoot and cleaning out the hoof, including the removal of all softened horn. An astringent lotion, used with daily hoof cleaning, aids recovery after removal of the diseased tissue. Use of a bar shoe after the disease has been stopped may help the frog regenerate. The outlook for recovery is usually favorable, but if the connective tissue of the frog has been damaged, all diseased tissue must be removed.

Last full review/revision July 2011 by Russell R. Hanson, DVM, DACVS, DACVECC; Joerg A. Auer, DrMedVet, Dr h c, MS, DACVS, DECVS; Andrew P. Bathe, MA, VetMB, DACVS, DEO, MRCVS; Leo B. Jeffcott, MA, BVM, PhD, FRCVS, DVSc, VD; Svend E. Kold, DMV, MRCVS, RCVS Specialist in Equine Surgery (Orthopedics); C. Wayne McIlwraith, BVSc, PhD, DSc, FRCVS, DACVS; Dale A. Moore, MS, DVM, MPVM, PhD; Sheldon Padgett, DVM, MS, DACVS; Tracy A. Turner, DVM, MS, DACVS, DABT; Stephanie J. Valberg, DVM, PhD, DACVIM; John F. Van Vleet, DVM, PhD