Mobile Equine Veterinary Service

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Dr. Porter @ 352-258-3571

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Friday, March 29, 2013

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. 

Friday, March 22, 2013

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

Thursday, March 14, 2013

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

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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...

Thursday, March 7, 2013

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.

Friday, March 1, 2013

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