Canine Herpesvirus-1 Affects Eyes by Carole Williams|
Field Spaniel Society of American Health Committee
As breeders, we're well aware of the danger of Canine Herpesvirus-1 (CHV-1) to pregnant bitches and newborn pups. Depending upon the stage of pregnancy when she is exposed, a bitch that has not previously had CHV-1 will resorb the pups and appear to be infertile, will have stillborn pups, or will deliver puppies who fade and die painfully one by one within a day or two of birth. The disease is known as Fading Puppy Syndrome.
"This puts breeders in a Catch-22 situation. At present, exposing breeding stock to the disease is the only way to prevent abortions and puppy deaths, but may lead to eye disease and blindness in older dogs."
Because of this danger, many breeders make sure their bitches have been exposed to the common virus before pregnancy. In adult dogs, it causes only mild respiratory disease or infection of mucous membranes in the genital tract. It's much like the "chickenpox parties" that predate the chickenpox virus vaccine, where mothers deliberately exposed their children to the disease.
Now veterinary scientists know that like chickenpox, the CHV-1 virus lingers in the dog's body long after disease symptoms are gone. Eric C. Ledbetter, DVM, DACVO, from Cornell University, presented information on his study of CHV-1 at the AKC Canine Health Foundation 2009 National Parent Club Canine Health Conference in St. Louis. This puts breeders in a Catch-22 situation. At present, exposing breeding stock to the disease is the only way to prevent abortions and puppy deaths, but may lead to eye disease and blindness in older dogs.
Investigating conjunctivitis, or pinkeye, in dogs, Dr. Ledbetter and his team isolated CHV-1 virus in the infected dogs, and were able to grow the virus in the lab and subsequently show that the virus caused infection in other dogs. Dr. Ledbetter calls CHV-1 the most common cause of conjunctivitis in dogs. Once the eye infection passes, the titers of antibodies against the virus fade rapidly, within about two weeks. After that time, there is no way of identifying that the dogs have ever been infected..
The virus also causes ulcerative keratitis and nonulcerative keratitis, both infections of the eyes' cornea. Dogs with weakened immune systems or those on steroids are particularly vulnerable. Owners should suggest that their veterinarians test for CHV-1 virus in dogs with these symptoms.
Since 95% of dogs in the United States have been exposed to CHV-1, Dr. Ledbetter says that antiviral drugs need to be tested to treat the eye disorders. In the future, he predicts a vaccine will be developed. A vaccine against CHV-1 exists in Europe, but has been tested only to reduce puppy deaths.
Other advances in eye disease Dr. Ledbetter discussed include:
- Genetic testing for inherited ocular diseases. Several tests exist now, and others are being investigated.
- Gene therapy-the next logical step after finding the genes that cause eye disease. Gene therapy is in the research stage now for several rare eye conditions.
- Vitreoretinal surgery-new surgical techniques for retinal tears and detachments.
New imaging techniques that offer "live biopsies", a means of seeing cells in the eye without surgery.
- New laser surgery for glaucoma that drops production of fluid in the eye by destroying some of the fluid-producing cells. A new endoscopic technique allows much more accurate surgery.
Carole Williams of Rainbow Creek Field Spaniels, has been breeding and showing Field Spaniels since 1993. She is cochairman of the health committee and vice president of the Field Spaniel Society of America. A former newspaper journalist, she served as Director of Information for Morris Animal Foundation for eight years.