Transplants for Pets: The New Frontier
Although potentially lifesaving, the procedure has physical and ethical consequences for owners and animals.
Joanne Healey Howl, DVM |
Posted: Sat Feb 10 00:00:00 PST 2001
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Chloe, a Lhasa Apso, turned her nose away from her dinner dish - a simple action that started her adventure two years ago at the outer edge of veterinary science. As the ounces, then pounds melted from Chloe's once-plump frame, her owner, Cindy Tozzoli of Westwood, N.J., began to worry. A visit to her veterinarian, Mary Anne Crawford of Oradell Animal Hospital in Oradell, N.Y., explained everything: Chloe's appetite was gone because she was suffering severe kidney failure. Traditional medical care offered little hope. "Basically all we could do was maintain her for a little while," Tozzoli said. "She might live a month, maybe a year." Chloe needed more than ordinary veterinary treatment could offer; she needed new kidneys.
In human medicine, organ transplants of almost every kind are considered routine. A person who receives a transplanted kidney today has a greater than 97 percent chance of living more than a year and may expect to live 10 to 20 years. Kidneys are also available for cats, with several surgical centers reporting one-year survival of about 71 percent. For a dog, however, the hope of a transplant of any kind is slim. "The dog is without a doubt the most difficult animal to transplant," said Clare Gregory, DVM, director of the Comparative Transplantation Laboratory at the University of California, Davis, School of Veterinary Medicine. "But
exciting advances are being made. Right now I'm more optimistic for transplantation in the dog than I've been for 10 years."
What makes a dog so hard to transplant? It's not the surgery. Doctors had perfected the techniques of transferring most organs from one dog to another by the early 1950s during studies for human organ transplantation. Today's surgeons say it's relatively simple to place a new liver, kidney, pancreas, heart, lung or bowel into a dog. The trick is getting the dog's body to accept the new organ (there's also an ethical dilemma, as detailed here).
"Dogs have an amazing aggressiveness built into their immune systems," Dr. Gregory explained. They simply don't tolerate foreign proteins inside their bodies, and it makes no difference whether the proteins belong to a disease-causing virus or a life-giving kidney. Humans and cats reject organs, too, but their immune systems are a bit more tolerant, making it easier to suppress the rejection with drugs. A tolerant immune system is why people and cats can carry viruses such as the immunosuppressive viruses (feline leukemia and human immunodeficiency virus) in their bodies for years, while dogs don't. "When dogs see an invader, they either get sick with the disease or they quickly get rid of it," Dr. Gregory said. "They almost never just live with it." Left alone, a dog's immune system will mount a savage attack on a transplanted organ, killing it within five to seven days.Page 1 | 2 | 3 | 4
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