Furr, an accomplished researcher and specialist in equine internal medicine, discussed the causes, symptoms, treatments, and methods of prevention for several neurological diseases and conditions including hypoxic ischemic encephalopathy (HIE), equine herpesvirus myeloencephalitis (EHV-1), botulism, wobblers and equine protozoal myeloencephalitis (EPM).

Highlights from the presentation are included below:

Hypoxic Ischemic Encephalopathy

Hypoxic ischemic encephalopathy--also known as dummies, barkers, convulsives, and neonatal maladjustment--occurs within the first three days of a foal's life. The condition is typically attributed to complications during delivery. Symptoms include dullness, failure to nurse, blindness, seizures, aimless wandering, and a lack of affinity for the mare. Foals suffering from HIE may be hypothermic but do not usually exhibit a fever. The condition of affected foals typically worsens for one to two days and then stabilizes and returns to normal function on days five through seven.

Hypoxic ischemic encephalopathy is diagnosed through physical examinations and history, and evaluation of the blood and spinal fluid. It is treated through the administration of intravenous fluids and nutrition, control of seizures, antibiotics, blood pressure support, and ventilation support. The prognosis for full recovery is 75% to 80% when the patient's condition is not complicated by infection. There are typically no long-term complications for survivors of HIE.

Equine Herpesvirus Myeloencephalitis-1

Equine herpesvirus myeloencephalitis-1 (EHV-1) is a viral infection that can lead to nervous system disease, respiratory disease, abortion, and genital infections. EHV-1 features the characteristic of latency and is spread by direct contact. Although this form is most commonly seen in older animals, it can affect horses of any age. Horses who contract EHV-1 typically exhibit a transient fever that follows a one-week incubation period. Additional symptoms include an abrupt onset of depression, stumbling in the rear limbs with weakness, and bladder and rectal paralysis.

Diagnosis of EHV-1 includes evaluation of clinical signs and history, as well as cultures of blood, nasal secretions, and cerebrospinal fluid. Antibody tests can also be used, although false negative results to these tests are common. Treatment for EHV-1 includes oral fluids and nutritional support, evacuation of the rectum and bladder, and anti-inflammatory drugs. 30 days of isolation and restricted movement is recommended for premises housing a horse that is suspected of having EHV-1. A quarantine period of 14 days for all incoming animals can aid in the prevention of the disease. The vaccines that are available for other forms of the Equine Herpesvirus are not effective against the neurological form of EHV-1.

Botulism

Botulism is a disease that is caused by the presence of the clostridium botulinum toxin and results in severe muscle weakness. In foals, it is known as "Shaker Foal Disease" and usually affects horses that are one to two months of age. In adults, it is known as "Forage Poisoning" and has an 80% fatality rate. Horses affected by botulism will drag their toes and exhibit muscle trembling, a weak or shuffling gait, lowered head and an overall dull appearance.

Diagnosis is made by evaluation of clinical signs, analysis of the stomach, blood and intestinal tracts, electromyography and post-mortem examination. A serum is available to neutralize the clostridium botulinum toxin once contracted. Supportive care includes nutritional and fluid support, oral laxatives, cleaning of wounds, mechanical ventilation and management of recumbency. Vaccination and proper cleaning of feed bins can help to prevent horses from contracting the disease.

Wobblers

Wobblers is another term for cervical spinal cord compression. A common cause of this spinal cord disease in young adult horses is cervical vertebral myelopathy (CVM). Wobblers is most common among 2- to 3-year-old Thoroughbreds but it can be seen in horses of all breeds and ages. Clinical signs of CVM include stumbling and tripping, an uncoordinated or unsteady gait that is worse in the rear legs than in the front legs, swaying of the body and erratic foot placement. It is often first noticed when horses are being broken or trained and is usually slow to progress.

Diagnosis of CVM is made through radiographs of the neck, calculation of sagittal ratios and myelogram. Nuclear scintigraphy can be useful in cases of trauma, osteomyelitis, or severe cervical arthritis. Surgical treatments include dorsal laminectomy, which provides immediate relief of compression, and interbody fusion in which vertebral bodies are fused using a surgical implant. Non-surgical treatments have been shown to have poor efficacy in treating Wobblers.

Equine Protozoal Myeloencephalitis

Equine protozoal myeloencephalitis (EPM) is a disease that affects horses of all ages and breeds. Research is currently being conducted to identify new diagnostics, treatments, and prevention methods for EPM. EPM leads to gluteal muscle atrophy, abnormal limb position, and masseter atrophy. It is diagnosed through tests that identify antibodies to the parasite including the Western blot, indirect immunofluorescence, an ELISA test and stall side screening test.

There are several medical treatments available for EPM including ponazuril (Marquis), nitazoxanide (NTZ or Navigator) and sulfadiazine/pyrimethamine (Re-Balance). Proper feed management techniques can decrease a horse's chances of contracting EPM. Examples include the removal of spilled feed and the cessation of ground feeding.

The Marion duPont Scott Equine Medical Center's next Tuesday Talk, "Acupuncture and Pain Relief for Horses," will be held on January 16, 2007." Details are available online at www.equinemedicalcenter.net or by contacting Amy Troppmann at 703/771-6843.

The Marion duPont Scott Equine Medical Center is a Leesburg, Va., based full-service equine hospital that is owned by Virginia Tech and operated as one of three campuses that comprise the Virginia-Maryland Regional College of Veterinary Medicine.