HEALTH - EPILEPSY
Canine Epilepsy
Scientists Continue the Search for Genetic Cause of Canine Epilepsy in Cocker Spaniels
“WE NEED FAMILIES WITH NORMAL AND AFFECTED MEMBERS. FROM THESE FAMILIES WE
HOPE TO IDENTIFY MARKERS LINKED TO EPILEPSY, OR THE MUTATION(S) RESPONSIBLE FOR CAUSING INHERITED SEIZURES.”
Liz Hansen Project Coordinator of the Canine Epilepsy Project Genetic researchers studying epilepsy are trying to learn how the disease is inherited in various breeds, including American and English Cocker Spaniels, and are looking for the gene or genes that may cause the disease. “Knowing the mode of inheritance will make the research easier,” says Barbara Licht, Ph.D., associate professor at Florida State University, who is studying epilepsy in Standard Poodles. “For example, if researchers determine that epilepsy in any given breed is recessive and that only one major gene is involved, then they know they are looking for a single gene and an affected dog has two copies of it. You have a better idea of what you’re looking for.” Though data is not available on the prevalence of epilepsy in Cocker Spaniels, the incidence among all breeds is about 4 percent, says Liz Hansen, project coordinator of the Canine Epilepsy Project at the University of Missouri.
The Canine Epilepsy Project is part of the Canine Epilepsy Research Consortium, a group of scientists
studying the disorder who have agreed to share information, collaborate on papers and release their findings to the public. The project involves a collaborative effort between researchers from the University of Missouri, the University of Minnesota, The Ohio State University and the Animal Health Trust in England. Grants from the American Kennel Club (AKC) Canine Health Foundation and the National Institutes of Health, as well as individual breed clubs, including the American Spaniel Club, and private donations, help to support the work. The researchers are collecting samples from as many affected dogs and their relatives as possible. “We need families with normal and affected members,” Hansen says. “From these families we hope to identify markers linked to epilepsy, or the mutation(s) responsible for causing inherited seizures.” So far, samples from 3,781 dogs representing 72 breeds have been submitted. Of these samples, 624 are from dogs affected with epilepsy –– 20 samples are from affected American Cocker Spaniels. There also is a good representation among other flushing breeds, including English Springer, Welsh Springer and American Water Spaniels. Flushing spaniels have similar profiles of the disease, Hansen says. “We are not sure just what that means, but it’s notable,” she says. One characteristic noted in flushing spaniels is that more males seem to be affected than females. The hope is that finding the gene in one flushing spaniel breed may help make it easier to find the gene in others. “Any genetic test developed will be offered to the public at as low a cost as possible,” Hansen says.
Diagnosing Epilepsy
Veterinarians diagnose primary, also known as genetic or idiopathic epilepsy, only after other possible causes of seizures have been ruled out. For example, a seizure can be caused by trauma to the head, a metabolic disorder, poisoning, an infectious disease affecting the central nervous system, or a tumor. Seizures from idiopathic epilepsy can begin at any age, but the common age range is from 1 to 5 years old. Unfortunately, the onset usually comes after a dog is old enough to have been bred. If a dog has a seizure, an owner should contact his or her veterinarian. The veterinarian should conduct a thorough workup including a physical examination, a complete history, blood work, bile acids assay or ammonia tolerance test to rule out liver problems, and a thyroid function test. If a referral is made to a neurologist, the consultation should include an evaluation of behavior, coordination and reflexes (called a neurological exam) and possible a brain scan (MRI or CT scan), spinal tap, or EEG.”
Epilepsy Treatment
If idiopathic epilepsy is diagnosed, a dog may be treated with anti-convulsant drugs such as
phenobarbital or potassium (or sodium) bromide. Since neither of the drugs is without side effects, the veterinarian and owner might choose to wait until seizures become more frequent or prolonged before starting an epileptic dog on them. Dawn Boothe, D.V.M., Ph.D., associate professor of veterinary physiology and pharmacology at Texas A&M University, has completed a study funded by the AKC Canine Health Foundation that examined the safety and efficacy of phenobarbital vs.
bromide. She found that both drugs have short-term side effects, which include grogginess, vomiting and increased hunger, thirst and urination. With the exception of vomiting, the side effects diminish with both drugs. Some dogs taking bromide were still vomiting six months later. Phenobarbital was more effective than bromide in eliminating and shortening the duration of seizures. Thus, for many dogs, phenobarbital may be the first choice for an anti-seizure medication. Though the study did not look at long-term effects of using either drug, phenobarbital can damage the liver with prolonged use. Also, phenobarbital more so than bromide interacts with many other drugs. For that reason, bromide might be a better first choice for older dogs or those on other drugs, Boothe says.
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