My horse has what?
Temporohyoid Osteoarthropathy 

J. Brett Woodie DVM, Dipl. ACVS 

It can be frustrating for an owner to observe seemingly unexplainable changes in his or her horse’s behavior, and alarming to watch these changes progress to acute neurologic symptoms. Frustration and alarm may turn to bewilderment when the veterinarian diagnoses the horse with temporohyoid osteoarthropathy.

Temporohyoid osteoarthropathy (THO) is a progressive disease of the middle ear, the temporohyoid joint, the stylohyoid bone, and the base of the skull.  There is no age, breed, or sex predilection. The underlying cause of THO is not fully understood.  There are many theories as to the cause of THO such as an extension of inflammation and infection from otitis media-interna (inflammation of the inner/middle ear) or guttural pouch infection, trauma, and osteoarthritis. Relatively few horses with THO have a history or evidence of a guttural pouch infection or otitis at the time of the diagnosis.  It is possible that THO is the result of degenerative joint disease rather than a bacterial ear infection or guttural pouch infection.   Regardless of the cause, inflammation induces bony proliferation at the articulation of the stylohyoid bone with the petrous portion of the temporal bone (located at the base of the skull-see photo).  This results in the fusion of the temporohyoid joint.  The hyoid apparatus is connected to the tongue and larynx.  Therefore fusion of the temporohyoid joint reduces the mobility of these structures.  A stress fracture of the petrous temporal bone and/or stylohyoid bone can result from the impaired mobility.  This can be caused by eating, vocalization, or normal tongue movement. 

Initial symptoms for THO are unfortunately non-specific signs that can point to a variety of possible medical issues or even non-medical behavior problems. Head tossing, ear rubbing, refusing to take the bit, refusing to position the head properly when ridden, pain on palpation at the base of the ear, and non-specific behavior changes are early clinical signs.  As it progresses, this disease can cause acute neurologic signs such as ataxia (loss of balance), head tilt, nystagmus (involuntary oscillation of the eyes), and facial nerve damage.  Signs of facial nerve damage include the following:  drooping (partial or complete paralysis) of the ear on the affected side, deviation of the muzzle away from the affected side, decreased tear production, and the inability to completely close the eyelids on the affected side.  Corneal ulceration is a common result of the decreased tear production and the inability to blink properly.  Dysphagia (inability to swallow properly) can occur but is rare.  Neurologic signs are seen following the development of a stress fracture of the petrous temporal bone or the stylohyoid bone.
Diagnosis is made through an endoscopic examination of the stylohyoid bone and its articulation (temporohyoid joint) within the guttural pouch (Photo, left: Notice enlarged appearance of stylohoid bone in abnormal image).   Imaging modalities such as skull radiographs, CT, and MRI are also useful diagnostic tools that can be used. 

There are two surgical treatments for THO-a partial stylohyoid ostectomy or a certohyoidectomy (removal of the ceratohyoid bone).  Removal of a portion of the mid body of the stylohyoid bone (partial stylohyoid ostectomy) results in a fibrous non-union in the bone that should interrupt hyoid forces to the temporohyoid joint is one option. Potential complications include damaging the lingual artery, the hypoglossal or facial nerve, and regrowth of the stylohyoid bone at the surgery site resulting in a recurrence of the clinical signs. 

Removal of the ceratohyoid bone removes the mechanical stress on the fused temporohyoid joint also.  The complication rate is much lower with this surgery compared to the partial stylohyoidectomy.  Ceratohyoidectomy is safer, less technically demanding, and provides a better surgical alternative.  

The prognosis and the length of time that the horse will need to convalesce is based on the severity of the clinical signs at the time of diagnosis.  In general the prognosis is good.  Most horses will return to their intended use.  There are cases where the neurologic signs may persist.  Rehabilitation can be as long as 2 years but many horses will have an improvement in the clinical signs within 30 to 60 days.

An important consideration is that surgical intervention should not be delayed.  Rapid intervention is the key to a successful outcome.   

Bonnie Barr VMD, Dipl. ACVIM

Cellulitis is diffuse inflammation and infection of the subcutaneous tissues.  In horses cellulitis most commonly involves the limbs, although it may occur in other areas of the body.  Commonly the dermal and subcutaneous layers of the tissue are affected although deeper more severe cellulitiscan occur.  Lesions can spread rapidly and dissect along tissue planes with devitalization and loss of skin.  The initial symptoms include acute swelling and lameness that involves one or more limbs.  The entire limb rapidly becomes two to three times the normal size and becomes hot and painful to the touch.  Cellulitis occurs more often in the hind limbs than the front limbs.  Accompanying systemic signs include increased rectal temperature and heart rate. 
Bloodwork often will reveal an increased white blood cell count and fibrinogen.  An ultrasound of the limb may identify a localized fluid pocket that can be aspirated for culture, although sometimes the ultrasound just confirms the diagnosis of cellulitis.  If there is a deep wound, a specimen can be obtained for culture.  Radiographs may be performed to rule out bony related causes for the lameness and swelling.  Cellulitis is usually caused by bacteria entering into the connective tissue.  A majority of the time an underlying cause is not determined or the wound may be small and superficial.  Cellulitis often occurs where the skin has previously been broken from cuts, scrapes, bruises or insect bites resulting in inoculation of normal skin bacteria or exogenous bacteria.  Normally the skin has many types of bacteria living on it, but where there is a break in the skin, bacteria can enter the body and cause infection and inflammation.  Cellulitis can also be secondary to recent injections of the limb, surgery or trauma.  The most common bacteria isolatedare Staphylcoccus aureus andStreptococcus species.  Other bacteria occasionally isolated include E. coli, Actinobacillus sp, Enterococcus sp and Pseudomonas sp.  It is often not possible to isolate a causative agent.        
Treatment involves broad-spectrum antimicrobials such as penicillin and gentamicin or trimethoprim-sulfadiazine.  Once the culture results are available, antimicrobials might be switched based on the susceptibility pattern of the bacteria isolated.  Non-steroidal anti-inflammatory agents, such as Bute or Banamine, are administered for pain and inflammation.  Hydrotherapy, bandages and hand-walking can also help to reduce the swelling.  Horses with deep seeded infections, devitalized skin or poor response to medical treatment may require surgical debridement or drainage.  Possible secondary complications include laminitis in the opposite limb, thrombosis of vessels in the affected limb, extensive tissue necrosis with loss of skin or lymphangitis.
In the literature it is reported that roughly 80-90% recover.   Horses that recover rarely regain the original contour of the limb and seem to be predisposed to re-occurrence.  Prevention includes such measures as carefully clipping long hair on the legs and keeping them clean and dry.  Avoid abrading the skin when cleaning the legs thus use soft brushes and sponges.  Frequent bathing may predispose the skin to drying and chapping, thus frequent bathing should be avoided or the limbs should be carefully dried afterwards.  Because bathing equipment may act as a fomite for the causative bacteria, it is best to clean the equipment on a daily basis and, if the horse is prone to cellulitis, have separate bathing equipment for that horse.  Finally wounds should be properly treated by a veterinarian.

Controversies of Equine Herpesvirus -1 Myeloencephalopathy
Stephen M. Reed DVM, Dipl. ACVIM

The most recent outbreak of Equine Herpesvirus myeloencephalopathy has finally subsided.  Once again this outbreak served to alert horse owners and veterinarians of how prevalent and devastating EHM can be and how rapidly it can spread across state and even country borders.  Work by Allen et al has shown that this Herpesvirus mutant has established a well-entrenched reservoir of latently infected horses.  Outbreaks of EHM have been observed since 1966 but appear to be increasing in frequency along with significant patient morbidity and mortality. Horses demonstrating neurological signs associated with outbreaks of EHV-1 were more sporadic prior to 2000. (Allen AAEP white paper and GP Allen AJVR 2007).  
The principal mode of transmission is horse to horse via the mucosal epithelium of the upper respiratory tract.   Recent episodes in the United States are the result of a mutant strain of the Herpesvirus, however it is important to remember that both wild-type and mutant strain of EHV-1 can cause neurological disease. Nasal shedding may last up to 14 days with clinical signs observed within 3 to 6 days after exposure.  To prevent disease in naïve animal’s best practicesshould include vaccine maintenance, although existing vaccines may not provide sufficient protection. Vaccine ineffectiveness may be a result of exposure to a large quantity of virus or exposure to a particularly aggressive strain of virus or suboptimal performance of currently available vaccines.
How do we know it’s EHM? Typical clinical signs may be very helpful with identification of infection by this virus.  These clinical signs include ascending neurological deficits such as poor tail tone, urinary incontinence, weakness and ataxia beginning in the pelvic limbs.  Identifying a significant rise in complement fixing or virus neutralization antibodies in acute and convalescent serum titers collected 7 to 21 days apart is useful. Tests such as PCR on nasal swabs or blood samples, viral culture, and immunohistochemistry may be used to establish a definitive diagnosis, although in some cases a post-mortem examination is required. 
The management of horses with suspected EHM should be directed at achieving a safe environment and providing excellent nursing care.  Isolation of horses which are suspected or known to have EHM is critical to help prevent spread from horse to horse.  The individual horse with obvious bladder dysfunction should quickly and as frequently as possible have aseptic evacuation of the bladder. Administration of anti-viral agents such as use of valacyclovir has been quite positive recommending doses of 27 mg/Kg three times a day orally for one week followed by 18mg/Kg twice daily for 14 days.
To reduce the risk of large-scale, farm wide outbreaks of EHM herd management procedures should be employed. The procedures considered to be the most effective are dividing the at-risk population of horses on the premises into smaller groups; keeping those sub-groups in closed, physically isolated units; and minimizing the stress caused to horses by crowding, poor nutritional state, heavy parasite infestation, lengthy transport, disruption of established social groups, inclement weather, en masse weaning, etc. Smaller group sizes with each group maintained under conditions that limit the transmission between the groups helps to maximize effectiveness. Management should restrict moving horses in and out of each established group and avoid any contact with transient horses. Adding a new horse to a closed group should be preceded by a 21 day isolation period.
Understanding the disease, following proper vaccination protocols along with best herd health practices are important factors for the horse owner to reduce the threat of EHM.  In addition, employing good biosecurity practices at home and away at competitions and knowing how to respond when outbreaks occur is critical in safeguarding your horse from the devastating impact of EHM.


Hats Off to Kentucky’s Horse Industry Day was instituted 7 years ago as an equine industry initiative to promote awareness of the state’s equine industry and its vital role in Kentucky’s past, present and future. On this special day, all Kentuckians are invited for a free afternoon of family fun and educational activities at the Kentucky Horse Park, the only day of the year where Park admission is free for the entire family. Since its inception the event has grown and become a favored day for Kentuckians to come to the Kentucky Horse Park to celebrate Kentucky’s claim as the Horse Capital of the World.

This year’s Hats Off Day – presented by Alltech with Official Partners Rood & Riddle Equine Hospital, Hallway Feeds and Spy Coast Farm was held August 6. Activities began at 4:00 p.m. with a giveaway of hats from equine businesses followed by fun, free activities including pony rides, educational booths, and interactive equine stations located in and around the fabulous outdoor Rolex Stadium at the Kentucky Park Horse Park.

At 7pm, the crowds turned their attention to the arena show which featured unique equine demonstrations including Australian horseman Guy McLean and his amazing  Horses (left), and an equine “Dancing with the Stars” duel between freestyle reining rider, Lyndsey Jordan and freestyle dressage rider Nicole Levy.

The day’s events concluded with the $50,000 Rood & Riddle Kentucky Grand Prix, a premier show jumping competition held annually for the past 25 years. Michael Morrisey and Vorst prevailed in an 8 horse jump off giving Morrisey back-to-back wins in this event.

The Grand Prix also serves as a charity fundraiser for the Kentucky Equine Humane Center and the Kentucky Horse Park Foundation, raising more than $450,000 for charitable organizations in Kentucky since 2002.

Rood & Riddle feels it is vital to support Hats Off Day and other initiatives that strengthen the equine industry which has a multi-billion dollar economic impact on Kentucky and generates 80,000 to 100,000 Kentucky jobs. “Around the country and the world, when people think of Kentucky, they think of horses,” said Dr. Tom Riddle. “Kentuckians should feel a great sense of pride in the champion horses that are raised here and come here to compete.”

Registration Open for Equine Upper Airway Symposium 

Registration is open for the4th annual Equine Upper Airway Symposium, scheduled for September 22-25, 2011, at the Embassy Suites in Lexington, Kentucky. The 3 ½ day symposium, sponsored in part by Rood  &Riddle, Optomed, and the ACVS  Foundation, offers an intense schedule of lectures and labs designed to present in depth, current information regarding pathophysiology, diagnosis, treatment, and prognosis for upper airway (UA) conditions in the horse. The target participants for the meeting are veterinarians in resident training programs and young clinicians who have not had the desired exposure to UA conditions in the horse. The number of participants will be limited to 40, restricted by available lab space. Participants will be accepted in the order the registration is received, with additional preference provided to those in residency training programs.  Registration is $450 for ACVS/ECVS residents and $900 for non-residents.

Complete program and registration information is available at

Opportunities in Equine Practice Seminar Benefits Students and Practitioners

For nine years Rood & Riddle has acted as organizing host and sponsor for the Opportunities in Equine Practice Seminar(OEPS), an annual meeting to promote equine practice to third year veterinary students.  The meeting is a cooperative effort funded by the American Association of Equine Practitioners, equine industry businesses and numerous private equine practitioners from across the U.S. and Canada.  Every Labor Day Weekend equine practitioners gather in Lexington to meet OEPS students to present their experiences in practice and offer opportunities for externship and internship training at their individual practices. Since its inception in 2003, over 3,500 veterinary students have attended OEPS making it the most successful recruitment arena for equine veterinary practice.

When veterinary graduation statistics showed a disturbing trend of declining numbers of new equine veterinarians, OEPS was launched as a proactive means to increase the number of veterinary graduates entering equine practice. In recent years that trend has stabilized and the seminar has evolved into a mentorship forum and recruitment opportunity for practices offering externships and internships.

The OEPS program has also evolved over the years. In addition to presentations from veterinarians discussing different practice discipline opportunities, the program includes financial and practice management advisors offering business information with professional and financial strategies for students to consider when they enter the job market.
“It has been rewarding to work with my colleagues around the country to mentor veterinary students entering equine practice,” stated Dr. Bill Rood. “We’ve adapted the program to reflect current trends in equine practice providing valuable information for both students and practitioners.”

The 2011 OEPS will bring nearly 400 veterinary students seeking information about equine veterinary careers to Lexington, Kentucky, September 2-4.

Pony Clubber to Veterinarian
Sarah Mouri, DVM 

Dr. Sarah Mouri is a 2011 graduate of the Atlantic Veterinary College in Prince Edward Island, Canada. She is currently expanding her equine veterinary skills and knowledge in a one year internship program at Rood & Riddle Equine Hospital. During the recent 2011 USPC Festival educational workshops, Dr. Mouri had the privilege of addressing young USPC members about her Pony Club experiences, encouraging them to use their Pony Club skills throughout life.  

 “Never tie a horse to a stall door!”  

Any graduate pony clubber may take this statement for granted. Of course, no one should tie a horse to a stall door or fence board for that matter. The horse should have a breakaway halter on and be tied with a safety release knot to an appropriate structure.  Having recently graduated from vet school, I’ve quickly learned to appreciate Pony Club words of wisdom in the professional world.  

The mission of Pony Club is "to provide a program for youth that teaches riding, mounted sports, and the care of horses and ponies, thereby developing responsibility, moral judgment, leadership and self-confidence.” I am a graduate B from the Middleburg Orange County Pony Club in Virginia. As an active member I competed at national rallies in Show Jumping, Quiz, and Combined Training. My Show Jumping team won overall and Horse Management in 2001 with zero points off the entire weekend. Anyone who has competed at nationals will understand the commitment to cleanliness involved!

Thanks to dedicated parents and volunteers, MOCPC has access to a variety of top equine professionals. I’ll never forget Dr. Jeannie Waldron’s treadmill and heart rate monitor demonstration, tours of Dr. Kent Allen’s Virginia Equine Imaging, and lectures at the Virginia Tech Mare Center on equine nutrition. In addition, summer camp, mounted lessons, and rallies were all centered around sportsmanship and providing individual care for your mount. I am extremely grateful to all those volunteers from my active pony club days.  I hope to give back to the organization that helped shape my interest in veterinary medicine and care of the equine athlete.  

I find myself using skills gained from Pony Club every day. As a Rood & Riddle intern for Dr. Spike-Pierce and Dr. Newton, I bandage a lot of horses! My “Teddy” had his limbs wrapped multiple times a day for practice before ratings. Thanks to his patience, bandaging is a skill I’ve developed well before vet school. A well placed bandage is something simple that serves the patient well and clients take note of.

Pony Club has given me a common language with clients who may be PC graduates themselves and/or have children currently involved. They may rest assured that I know how to clean every inch of a horse, I have communication skills thanks to the oral tradition of ratings, and I will not be tying their ponies to any stall doors. The knowledge and practical experience from my MOCPC days have helped me navigate the long and sometimes rocky road to becoming a veterinarian. I know I will continue to use my “pony Club skills” for many years in the future.

Around the Practice . . . 

The 26th Rood & Riddle Intern Class began their one year training program earlier this summer.  This year’s hospital interns are Dionne Benson DVM, veterinary graduate from University of Minnesota; Jen Godfrey DVM, Washington State University; Jim Maxwell DVM, Virginia Tech; Sarah Peters VMD, University of Pennsylvania; Sheena Roles DVM, Oklahoma State; Ashley Homm DVM, Auburn University; Ashley Edge DVM, St. George’s University; and Nikki Dalesandro DVM, Purdue University. Interns training with our ambulatory veterinarians are Ashley Embly DVM, University of Georgia; Anna Hichborn DVM, University of Georgia; Sarah Mouri DVM, Atlantic Veterinary College; and Abbie Holland-Cullen DVM, from Michigan State University. Rood & Riddle, which offers hospital and field service internships annually, has graduated 224 veterinarians from the program since its inception in 1986.

Rodney King (left) and Jonathan Nunn were winners in Creative Forging Congratulations to Farrier Rodney King NZCEF, CJF, AWCF, for honors earned in the World Championship Blacksmith competition at the 2011 Calgary Stampede July 6-10. Rodney, representing his native country of New Zealand, placed 9th overall in the “Shoe to Fit” class. He also teamed up with farrier Jonathan Nunn from England to win first place in “Creative Forging.” The Championship, known as the “Olympics of Blacksmithing” annually draws the world’s top blacksmiths to Calgary to compete in a series of forging, horseshoeing and team events. (Photo: King, left and Nunn holding first place ribbons from the Creative Forging competition).

Rood & Riddle Veterinarians were actively involved with the recent US Pony Club Festival Education workshops, held at the Kentucky Horse Park. Rood & Riddle presentations included, “From Pony Clubber to Veterinarian” presented by Dr. Sarah Mouri; “Practical Equine Chiropractic Applications” by Dr. Alex Emerson; “Pre-purchase Exams – Important Information for the Buyer and the Seller” and “Conditioning Your Sport Horse” by Dr. Chris Newton; “Performance Dentistry” by Dr. Brad Tanner; “Understanding and Addressing Colic” by Dr. Hannah Wellman; and “Lameness in the Foot & Hoof Care” by Dr. Fred Peterson.

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