Arytenoid Chondritis in a Horse

A 12 year old quarter horse mare presented for a 2-3 month history of coughing and "wheezing". The mare had developed the symptoms some what suddenly and was responsive to systemic corticosteroids. As such, it was initially thought that the mare was developing signs of heaves or COPD (chronic obstructive pulmonary disease). Heaves is relatively common in the southeastern United States and is a chronic progressive condition that involves an allergic condition that affects the lungs and causes fibrosis and scarring.     At presentation, the client was interested in finding out for sure what was causing the coughing and wheezing. Re-breathing exam was essentially normal with no wheezing detected or coughing. The mare was currently being treated with corticosteroids and had been for the past 48 hours. The initial plan was to scope the mare and perform a bronchoalveolar lavage (BAL) to confirm the diagnosis of heaves. However, when the endoscope was passed to the point of the larynx, we discovered what was the true problem!

Figure 1

In Figure 1 and 2, the larynx of the horse in question appears grossly abnormal. In Figure 1, the horse is in between breaths and there is thin slit between the arytenoids which consists of her airway. In Figure 2, the mare is taking a deep breath and the full extend of her airway is probably the diameter of a sharpie pen! There is large linear ulcer that crosses the left arytenoid cartilage and the significant thickening of both left and right arytenoid cartilages suggest chronic inflammation. In Figure 3, a "normal" endoscopy demonstrates what the full extent of the airway should be during inspiration and what normal arytenoid cartilage should look like!

Figure 2

Figure 3

Arytenoid chondritis is a relatively common cause of coughing and nasal discharge in older horses. This mare was a bit on the young side to have developed this condition. The causative agent is not clear but it is believed to be a combination of chronic irritation that is made worse by bacterial infection. In my experience, I have diagnosed this problem in horses that were exposed to a chemical irritant in agriculture setting such as dairy farms and produce farms; however, I have not been able to determine what chemical is causing the problem. Unfortunately  once the condition becomes chronic and the arytenoids are permanently disfigured, the only viable option is to perform a permanent tracheotomy. Surprisingly  horses do very well with permanent tracheotomies as long as they do not go swimming!! Clinical signs will improve with systemic corticosteroids and throat spray however these treatments will NOT reverse the damage done!!  This case, once again, demonstrate the importance of an endoscopic exam EARLY in the disease process.

White Line Disease and Laminitis in a Horse!

Figure 1

 The radiograph in Figure 1 is that of a middle-aged gelding that presented for intermittent foot pain. One year prior, the gelding had developed a high fever of unknown origin (presumed viral). During the weeks that followed the high fever, the gelding was slow to walk in small circle and on concrete surfaces. Over several months, the gelding's lameness improved however he was consistently tender immediately after being trimmed by the farrier.  There are 2 disease processes identifiable in Figure 1. The first is chronic laminitis or founder.

Figure 2

 In Figure 2, the yellow lines correspond to the dorsal hoof wall and the dorsal aspect of the coffin bone. Normally, these lines are parallel to each other such that a horizontal line drawn across them would yield equal angles (angle A and angle B). However, when the coffin bone has "rotated" from its axis then the angles will differ as they do in Figure 2. Hence, the radiographic finding is consistent with laminitis (founder) and subsequent coffin bone rotation. This condition appears to be chronic, evidenced by the "flaring" of the tip of the coffin bone seen in the blue circle in Figure 3. This flaring often corresponds to small fractures of the tip of the coffin bone secondary to increase concussive forces over the toe region of the foot. The red arrow highlights the extremely thin sole which measured less than 5 mm!  Ideally, the sole depth at the tip of the coffin bone should measure between 10-15 mm in thickness.

Figure 3

 The second disease process noted in these radiographs is White Line Disease. This is evidence by the gas lucency traveling up the dorsal hoof wall (yellow arrows in Figure 4). The lateral radiograph is only 2 dimensional hence it is impossible to predict if this gas lucency is right down the middle of the hoof or if it wraps around the medial and lateral aspect of the hoof. Regardless, the gas lucency corresponds to separation of the hoof wall from the underlying tissue. White line disease may be the primary problem or secondary. In this case, it is likely secondary to the chronic founder/laminits however in primary cases, it can cause coffin bone rotation and result in laminitis. This condition results from the accumulation of dead/decaying material that slowly works its way from the sole surface up the hoof wall. The offending organism is believed to be in part anaerobic bacteria that thrive in a low-oxygen environment and produce gas that can be seen on a radiograph. Excessive gas accumulation may result in hoof wall separation from the coffin bone and coffin bone rotation.  Treatment involves aggressive removal (hoof wall resection) of ALL dead and decaying hoof wall to expose the offending organisms. Hoof wall resection along is very effective in treating this condition but it is typically paired with soaking the foot after resection in a variety of solutions to kill off the offending organisms.

Figure 4

Often, the early signs of white line disease can be detected at the time of hoof trimming and appear as a shallow crack at the toe region. The opposite foot of this horse had the very beginnings of white line disease evidenced by a small amount of gas lucency noted at the very tip of the hoof (Figure 5). When identified at this early stage, the condition is easily managed with regular balanced 4-pt trimmings by the farrier. Successful  management of white line disease is best accomplished through a farrier-veterinarian team effort. The farrier is the most important part of the team since they will be doing 99% of the work. The veterinarian will provide the radiographic studies to verify that adequate exposure of the diseased foot is accomplished.

Figure 5

EPM in a Horse

A middle-aged Quarterhorse gelding presented for a history of strange gait and apparent pelvic limb weakness. The clinical signs developed suddenly over 24 hours. The gelding was current on vaccination for West Nile virus, Eastern Equine Encephalitis, and rabies. Neurologic exam noted a gelding in good body condition, alert, responsive yet quite "wobbly" in the hind limbs. Closer examination of all 4 limbs revealed severe weakness in both hind limbs. The degree of weakness was significant enough that the horse was having difficulty remaining standing. Importantly, the hind limb weakness was NOT symmetrical but was more severe in the left hind limb compared to the right hind limb. In the video below, the gelding is bearing most of his weight on the forelimbs and the result is a tendency to spin on the hind limbs due to the severe weakness of the pelvic limbs. 

Based on the neurologic exam, the most likely disease processes affecting this horse include Equine Protozoal Myeloencephalitis (EPM), spinal cord trauma, Eastern Equine Encephalitis (EEE), and West Nile Encephalitis. The sudden or acute onset of clinical signs is most consistent with spinal cord trauma however there was no history of a traumatic event and there were no external signs of such. Equine Protozoal Myeloencephalitis typically does not develop such severe signs over night however such clinical history is possible. The likelihood of either EEE or West Nile virus encephalitis is low in a well vaccinated horse yet not impossible! Diagnosis of encephalitis is dependent on serum testing and confirmation of EPM is dependent on testing of cerebral spinal fluid (CSF). Cerebral spinal fluid can be collected from two location including the atlanto-occipital (AO) joint space and the lumbo-sacral (LS) joint space. It was determined to collect CSF from the LS region. This option was chosen since it would be performed in the standing horse with moderate sedation. Collecting CSF from the AO site typically requires short term anesthesia and the ability of this horse to rise from recumbency was questioned. CSF fluid was collected and submitted for testing. The sample was positive and EPM was confirmed as the disease process in this horse. He is currently being treated with a variety of medications/supplements and the client is committed to treating for 4-6 months.

Read more about EPM @

http://www.aaep.org/health_articles_view.php?id=248

Stifle OCD!!

A yearling thoroughbred presented for sudden lameness and swelling around the stifle joint. The filly had been purchased several months prior from a select thoroughbred sale and repository radiographs were performed at the time of purchase. At the time of purchase, the filly was sound, there was no effusion of the stifle joint and there were no obvious radiographic changes noted in either stifle joint. When the filly presented for lameness, the stifle radiographs were repeated. Close inspection of the lateral trochlear ridge suggested irregular contours (yellow arrows inside blue box, Figure 2) of the trochlear ridge along the mid body region (Figure 1 and 2, blue box). Based on the radiographs alone, the filly was treated with intra-articular Hylartin and forced stall rest for 30 days.

Figure 1

Figure 2

Unfortunately, the filly remained lame after 30 days of stall rest and a follow-up exam included an ultrasound evaluation of the stifle joint. The ultrasound exam revealed significant changes along the lateral trochlear ridge which were not fully appreciated on the radiographic exam. In Figure 3, the lateral and medial trochlear ridge are displayed. The bony surfaces of the trochlear ridges appear as a bright white lines and the cartilage as  thin black lines that follow the contour of the bony surface. Any disruption of the bony surface/cartilage will appear as a mix of disrupted white lines and black pockets. In Figure 3, the image on the left is of the lateral trochlear ridge and there is clearly disrupted bone and cartilage along the bony surface.

Figure 3

In Figure 4, the lateral trochlear ridge is imaged in a longitudinal plane to assess the length of the defect. Irregular bone/cartilage appears to extend for several centimeters along the length of the trochlear ridge (yellow lines). The filly was referred for arthroscopic exam and a large bone/cartilage defect was identified on the lateral trochlear ridge consistent with a osteochondritis dissecans or OCD lesion.

Figure 4

Osteochondritis dissecans is defined as a disorder that results in cracks in the articular cartilage and underlying subchondral bone. The "cracks" and cartilage separation result due to lack of blood flow to the region resulting in avascular necrosis of the tissues involved.  This condition is considered in part a hereditary disorder AND nutritional.  Unfortunately OCD lesions are common in young horses that were bred for sport such as racing thoroughbreds, performance quarter horses, and warm blood breeds.  Some cases of OCD can be managed with surgical intervention however the OCD lesion in this filly's stifle was so large that there was no hope for soundness. This case is a good example of the benefit of multiple imaging modalities in diagnosing the source of lameness in the equine stifle.

Resolved Aspiration Pneumonia

Approximately 2 months ago a young warm blood gelding presented for a 4-6 month history of chronic coughing, bilateral nasal discharge, poly-synovitis, and failure to thrive. At presentation, the gelding was in poor body condition and there was a moderate amount of nasal discharge which consisted of mucus mixed with feed/hay. Auscultation of the thorax noted abnormal lung sounds, bilaterally.  As I reported previously, endoscopic exam revealed feed material within the larynx and trachea (Figure 1 and 2). The feed material was noted through out the entire trachea and a trans-tracheal wash revealed the presence of feed material and bacteria in the cranial ventral lung lobes! The gelding was diagnosed with dysphagia and aspiration pneumonia.

Figure 1

Figure 2

Based on the trans-tracheal culture results the gelding was treated with oral antibiotics for 30 days. In addition, he was treated with systemic anti-inflammatory medication and systemic anti-arthritic medication. Once the antibiotic treatment was started, the coughing episodes subsided but were not completely abolished. The gelding began to gain weight and for the first time was seen laying down to sleep and roll in the pasture! A follow-up endoscopy performed at the end of 30 days of antibiotics revealed feed material within the larynx (Figure 3) and an intermittent dorsal displacement of the soft palate (Figure 4). Mild to moderate ulcerations were noted along the caudal edge of the soft palate when displaced. At this point, we were not sure what was going to happen once we stopped treating with antibiotics however based on the continued presence of feed material in the pharynx, it was assumed that a recurrence of aspiration pneumonia was soon to follow.

Figure 3

After discussing the limited options with the owner, it was decided to pursue acupuncture as a potential source of treatment. Dr. Marilyn Maler was asked to examine the gelding and provide her expert opinion and treatment options. She immediately instituted an acupuncture regiment that was directed at treating the horse's difficulty with swallowing among other points of interest. According to the owner, the gelding's cough improved significantly and in a short period of time was completely absent! The gelding continued to gain weight and has been eating "normally" for over 4 weeks. A follow-up exam was performed 2 days ago and the gelding's condition has improved so dramatically that I did not even recognize the horse!  Endoscopic exam noted NO feed material in the pharynx and normal lung sounds!! The gelding has a long way to go but our conversation has shifted from when might it be time to "do the humane thing" to when might it be time to ride him!!  This case is a strong reminder of the benefits of acupuncture for treating chronic diseases and I wish to extend a special thanks to Dr. Maler for all her help!!

Figure 4

Final note: On the day of the most recent exam, the gelding was feeling so good that he played hard to get. So, he was enticed with several hand fulls of feed just prior to the endoscopic exam. This happens to be a crude method of detecting dysphagia in horses and the gelding passed with flying colors!!

Figure 5

Coffin Bone De-Rotation!!

Approximately 6 weeks ago, a middle aged mare presented for chronic founder and non-weight bearing lameness. At presentation, there was significant rotation of the coffin bone in the lame foot (greater than 15 degrees) and reduction in the sole depth at the toe region (Figure 1-3). Due to the severe degree of coffin bone rotation and lameness it was determined that transection of the deep digital flexor tendon was the best option for the mare. The procedure was performed at the barn with sedation and a regional block.

Figure 1

Figure 2

Figure 3

In addition to transection of the deep digital flexor tendon, corrective shoeing was achieved by an expert farrier who specializes in foundered horses  (Sir Adam Whitehead). Corrective shoeing is as important if not MORE important than the surgical procedure and without it the procedure could not be a success! The mare's lameness has slowly improved over the past 4 weeks and follow up radiographs revealed complete DE-ROTATION of the coffin bone (Figure 4).  The palmar angle (blue line) is now approximately zero degrees with respect to the horizon and there has been a moderate increase in the sole depth at the toe region (yellow arrow).

Figure 4

In my experience, horses coffin bone rotation that exceeds 15 degrees benefit greatly from this procedure. Typically, these horses require 4-6 months from time of surgery before they are barefoot and sound in the pasture. This mare's initial recovery was slowed due to a sub-solar abscess that involved her entire sole and communicated with the coronary band. 

Guttural Pouch Fungal Infection Resolved!!

Back in January, a gelding presented for a history of recurrent nasal discharge. Endoscopic exam revealed the presence of a fungal infection within one of the guttural pouches (Figures 1 and 2) . A bacterial and fungal culture was performed on fluid/debris collected from the pouch. The bacterial culture was negative however the fungal culture was positive for Cladosporium spp. This species of fungi is very common in the environment, especially in the presence of moist or wet wood. In humans, it is a big player in fungi induced allergies. Interestingly, this species of fungi has not been described in the guttural pouch of a horse previously!

Figure 1

Figure 2

The gelding was treated with a specific anti-fungal medication given by mouth daily. After 4 weeks of treatment, there was a 50% reduction in the size of the fungal plaque and the degree of inflammation (Figures 3 and 4).

Figure 3

Figure 4

After 2 months of treatment there has been complete resolution of the fungal infection and inflammation (Figures 5 and 6). The stylohyoid bone remains slightly thickened compared to the opposite stylohyoid bone (Figure 7) however this will like resolve over the next 3-6 months. This case is unusual in several ways. First, the species of fungi has not been described before in the guttural pouch of a horse, secondly, most guttural pouch fungal infections include bleeding (epistaxis) thirdly, there are few reports of successful treatment of guttural pouch fungal infections in horses with JUST systemic anti-fungals.

Figure 5

Figure 6

Figure 7

Fibrosarcoma in a horse!

A 14 year old gelding presented for a complaint of recent lameness and swelling of the right knee or carpus. There was no history of trauma but a plumb size swelling was palpated along the outside of the knee. The gelding resented direct pressure over the knee and any manipulation of the knee. When radiographed, there were no significant abnormalities noted with regards to the bones or articular surfaces that make up the carpus. However, a moderate soft tissue swelling was noted along the dorsal (front) and lateral (outside) aspect of the carpus (Blue circles in Figures 3-4). 

Figure 1

Figure 2

Figure 3

Figure 4

An ultrasound exam was performed on the soft tissue swelling and a hypoechoic (dark) soft tissue structure was identified (Figure 5). This structure appeared well demarcated and was consistent with a mass or tumor which was below the surface of the skin yet outside the joint capsule of the carpus.

Figure 5

When the ultrasound image is flipped into the same projection as the radiograph, the soft tissue mass aligns perfectly with the soft tissue swelling noted on the digital radiograph (Figure 6). The red line corresponds to the middle carpal joint and helps demonstrate how close the tumor is to the joint yet does NOT communicate with the joint.

Figure 6

A core biopsy was taken of the soft tissue mass through a small skin incision directly over the area in question and submitted for analysis.  The histopathology report indicated that the core biopsy was consistent with a fibrosarcoma. This type of tumor is not common in horses and although it does not commonly spread to other regions of the horse, it can be locally destructive and aggressive. As such, it was determined that the immediate course of action was intra-lesional injections of a potent chemotherapy drug. Due to the close proximity with the joint capsule, surgery was considered too risky at this point. The gelding has been treated 1x with a chemotherapy medication and a follow-up exam is expected within 2-3 weeks. To be continued...

Osteochondroma in a horse!!

 The radiograph in Figure 1 corresponds to the carpus of the horse which became lame ONLY after heavy work. Once he was lame, the lameness was resolved by injecting carbocaine into carpal joints. Careful radiographic examination of the carpus and the surrounding structures noted a bony protuberance along the distal, palmar aspect of the radius (Figure 1 and 2). This finding is consistent with an osteochondroma formation. In humane medicine, an osteochondroma is defined as " an abnormal, solitary, benign growth of bone and cartilage, typically at the end of a long bone". In horses, osteochondroma formation is not common however when it does occur, the occurs commonly along the lower end (distal) aspect of the radius. In this location, the osteochondroma may cause irritation to the surrounding soft tissue structures including the carpal sheath. 

Figure 1

Figure 2

In Figure 3 and 4, an ultrasound exam was performed of the distal radius to determine if the osteochondroma was the source of the lameness. Two irregular lines (yellow lines) can be seen on the ultrasound exam which are consistent with the bony protuberances noted in the radiographs. In addition, the surrounding tissue is irregular with pockets of edema and there is a large accumulation of fluid within the carpal sheath (Red star). 

Figure 3

Figure 4

When the left and right forelimbs were compared via ultrasound (Figure 5), there is no evidence of an osteochondroma in the normal leg (right) compared to the left leg. A needle was placed into the pocket of fluid within the carpal sheath and blood tinged synovial fluid was collected. Following fluid aspiration, the carpal sheath was treated with cortisone, antibiotic, and Hylartin V. Most osteochondromas in horses are surgically removed and the prognosis is good for full return to work.

Equine Herpes Virus-1

What is EHV-1?

The acronym EHV-1 refers to Equine Herpes Virus -1 which is one of 4 varieties of the equine herpes virus complex (EHV-1, EHV-2, EHV-3, and EHV-4). EHV-4 is associated with upper respiratory disease in horses where as EHV-1 is associated with respiratory, neurologic, abortion, and foal death. EHV-3 is also known as coital exanthema and is a sexually transmitted disease in horses. This family of viruses is found in horses all over the world and it is unclear why some horses develop the neurologic form of this disease complex.

How is EHV-1 transmitted?

Transmission of the virus from one horse to another is dependent on 1: direct contact (nose to nose), 2: indirect contact via contaminated items and 3: aerosolized fluids (coughing or sneezing). Aerosolized fluids may travel up to 35 feet! The virus may survive for up to 30 days in the environment if the conditions are ideal. Once horses are infected they become latent carriers for the remainder of their life. They may become spontaneous "shedders" during periods of stress!

What are the clinical signs?

Incubation period is typically 6-8 days (time from exposure to onset of clinical signs) however it has been reported to be as long as 21 days!

Common clinical signs may include fever, depression, inappetance, upper respiratory infection, and abortion.
Neurologic signs range from temporary ataxia (in-coordination), urinary incontinence, rear limb weakness (dog sitting), complete paralysis and death. Death may occur within 24 hours of the onset of neurologic signs!!

How do you diagnose and treat horses with EHV-1?

Detection of EHV-1 in horses may be through PCR testing of nasal swab or blood, serologic testing, virus isolation and post-mortem exam.

Treatment is based supportive care which may include IV fluid therapy, anti-inflammatory medication and in some cases anti-viral drugs. There is no specific medication to treat EHV-1 in horses!!

Does vaccination protect horses from EHV-1?

There is no commercially available vaccine that prevents the disease! However there are several vaccines which are believed to reduce nasal shedding and hence limit the spread of disease. These include Rhinoimmune (Boehringer Ingelhein), Calvenza (BI), Pneumorabort-K (Pfizer) and Prodigy (Merck). Vaccination during an outbreak is recommended ONLY if there is a history of being vaccinated previously with these vaccines. Recommended to vaccinate every 3-6 months.

What should you do in the face of an outbreak?


Encourage barn personnel to disinfect clothing, shoes, and hand-wear at the entry and exit of all barn areas.

Monitor rectal temperature daily in horses exposed to known EHV-1 positive horses.

If your horse has been exposed to a horse known to be positive for EHV-1, a 21 day isolation protocol is necessary! Isolation area must consider the potential for a 35 foot range of aerosolized mucus.


Additional information may be viewed at the following sites:

AAEP and EHV-1

UF Veterinary Hospital and EHV-1

Department of Agriculture in Florida and EHV-1