Subcutaneous Pythiosis in a Horse

.A 10 year-old warmblood gelding presented to PHD veterinary services for the complaint of a swollen left front fetlock that was associated with a chronic draining wound. The recent history included a biopsy of the wound and diagnosis of pythiosis per histopathology. The gelding was treated with a single dose of a systemic pythiosis vaccine. In Figures 1 and 2 the yellow arrows are pointing to the firm swelling that is directly on the backside (palmar aspect) of the fetlock joint. In addition, the red arrow in Figure 2 corresponds to the chronic draining wound. The gelding was sensitive to direct pressure over the swelling, passive flexion of the fetlock and was mildly lame at the trot.
.
.

Figure 1

Figure 2

An ultrasound exam was performed of the area in question. The firm swelling consisted of multiple fluid filled structures along with focal areas of apparent mineralization. The structure appeared embedded within the distal annular ligament; however the superficial flexor tendon (SDF) and the deep digital flexor tendon (DDF) appeared to be normal. In Figure 3 the yellow arrows are highlighting the fluid filled structures. This case is a very unusual presentation for pythiosis in a horse. The majority of cases present with an external lesion as seen in Figure 4. As external lesions there are several treatment options which involve aggressive surgical de-bulking and various topical medications. The pathogen responsible for this condition is found in stagnant water and invades superficial abrasions that might be present any where on the horse. Hence the lower limbs are most commonly affected but it has been diagnosed in the naso-pharynx and GI track of horses.

Figure 3

Figure4

Because of the complicated location of the lesion in this horse, we elected to treat with a potent anti-fungal medication known as Amphotericin B. The medication was administered through a vein in the lower limb using regional limb perfusion. This technique maximizes the local perfusion of the soft tissues with the medication and minimizes the systemic effect of the medication. 

Figure 5

The lesion was re-evaluated 30 days after the initial treatment and there was approximately 40-50% reduction in size of the lesion. However, after 60 days, the lesion appeared to resume growth and a second treatment with Amphotericin B was recently administered. In addition, the gelding as received 2 vaccines against the pythiosis and will likely receive another. Because of the location, surgery is not an option for this horse hence the systemic therapy is our best option at this point. The case is on -going and the blog will be updated as we go!!

Figure 6

Severe Navicular Disease in a Horse

.
.A 10 year-old thoroughbred gelding presented to PHD veterinary services for the complaint of intermittent forelimb lameness. The gelding was purchased several months following a prepurchase exam performed by a local veterinarian. The buyer opted for NO radiographs at the time of the prepurchase considering that the horse was sound. Unfortunately, within several months after purchase, the gelding developed a lameness in the right front foot which was intermittent. The client contacted  PHD veterinary services for foot radiographs and a lameness exam. The lameness exam noted NO lameness in the forelimbs but rather a mild to moderate lameness in both hind limbs after flexing the upper limbs (hocks/stifles). The gelding was not positive to hoof testers in either forelimb. A radiographic exam was elected to document the palmar angle and sole thickness in both front feet. The image in Figure 1 is a lateral image of the right front foot and Figure 2 is a lateral image of the left front foot. The yellow arrows are highlighting the navicular bone of each foot.

Figure 1

Figure 2

Interestingly, the lateral image of the suspect foot (right front) appeared normal however the lateral radiograph of the left front foot was highly abnormal. The navicular bone of the left front foot was flattened and completely sclerotic when compared to the navicular bone of the right front.foot. Additional views of the navicular bone are imaged in Figures 3 and 4.  In Figure 3, the skyline projection of the navicular bone suggests severe deterioration of the bone and what appears to be a chronic fracture of the navicular bone (yellow arrow). The flexor surface of the navicular bone is very irregular.

Figure 3

In Figure 4, the distal border of the navicular bone is imaged. The yellow dotted line outlines the navicular bone and the yellow arrows are pointing to the many dark circles which are consistent with areas of lysis and/or cyst formation. The findings in Figures 3 and 4 are consistent with SEVERE degeneration and likely chronic fracture of the navicular bone. 

Figure4

These findings are NOT consistent with the physical exam findings of a sound horse or the history unless this horse has had the nerves, which provide innervation to the foot, surgically transected (nerved). At the time of the exam, the gelding did demonstrate sensation to the skin along the heel bulbs however there were small scars consistent with a previous surgery over the neuro-vascular bundles. Considering how normal the right front navicular bone appears, the degeneration of the left front navicular bone is most likely due to a septic process from a penetrating foreign body that resulted in infection of the navicular bone or a traumatic fracture. Regardless of the cause, these radiographic findings are suffice to retire this horse from forced exercise and hope that he remains comfortable for an extended period of time. This case represents another example of the benefit of simple foot radiographs as part of all prepurchase exam.

Ionophore-free Horse Feed Mills

The two bags of horse feed shown below were produced in IONOPHORE-FREE mills!! Why is this important??  In the past year there has been at least two well publicized cases of horses ingesting feed that was contaminated with a common supplement for cattle known as ionophores. The first case involved a barn full of horses in south Florida which ingested contaminated feed. Initially, three horses died however the remainder of the 22 horses were expected to eventually die due to the toxin in their feed.http://www.sun-sentinel.com/local/broward/fl-sick-horses-davie-20141121-story.html  The story is heart breaking however it could have been prevented.

 Recently, there was another reported incident of horses becoming ill and dying from contaminated feed. http://www.poisonedpets.com/deadly-horse-feed-still-sale-adm-alliance-refuses-pull-feed/ . Once again, the feed appeared to be contaminated with the supplement for cattle, ionophores. Ionophores are extremely toxic to horses and attack the muscle of the heart. If the horse does not succumb initially, it is likely that the diseased heart muscle will slowly weaken resulting in heart failure and death.. How can horse owners and trainers avoid the possibility of such a tragic occurrence?? By purchasing horse feed from ionophore-free mills. Most feed companies produce feed for various types of livestock including cattle and horses. In addition, it is common practice for some feed companies to produce cattle and horse feed in the same facility. These feed companies practice techniques to "flush" the cattle supplements out of the system prior to producing the horse feed. Clearly, there is room for error. The solution is to buy feed from documented, ionophore-free mills. If your horse feed representative is not capable of saying the words "ionophore-free mill" then its time for a change in feed!!!

Proximal Suspensory Desmitis in a Horse

A 10 year-old warm-blood gelding presented to PHD veterinary services for the complaint of forelimb lameness. During the lameness exam, it was noted that the gelding was moderately lame in the right front limb and the lameness appeared worse when the horse was lunged at the trot in a circle to the left. Palpation of the limb noted only mild response to pressure over the proximal suspensory ligament (back side of the limb, just below the carpus). A series of nerve and joint blocks were performed to isolate the source of the lameness. Once the proximal suspensory ligament was "blocked" the horse's lameness improved significantly. Therefore, an ultrasound exam was performed of the soft tissue structures of the right limb with emphasis on the proximal suspensory ligament. Figures 1 and 2 correspond to the proximal suspensory ligament. The yellow line outlines the body of the proximal suspensory ligament in cross-section and the blue arrows a bright (hyperechoic) lesion within the suspensory ligament. The area of increased brightness or echogenicity is consistent with an enthysophyte. In addition, the enthysophyte was surrounded by an area of decreased echogenicity consistent with edema or active inflammation. An enthysophyte is a abnormal bony projections at the site of attachment between a tendon/ligament at bone. In this case, between the proximal suspensory ligament and the third metacarpus (cannon bone).

Figure1

Figure 2

In a similar case, the horse was subjected to a CT (computed tomography) exam and the enthysophytes appear as small, spikes (blue arrows) which are projecting into the body of the suspensory ligament (yellow outline). From this view is understanding why these horses have chronic and recurring forelimb lameness issues. The presence of enthysophytes tends to worsen the prognosis with regards to return to "full" work.

Figure3

The above mentioned gelding was treated with rest, multiple PRP (platelet rich plasma) injections, and shockwave treatment. He is currently sound however his prognosis remains guarded for full return to work and show.