Preventing the Incurable

So far as man and his domesticated animals are concerned, rabies is under control in the U.S. Last year only one person died of the disease--one-tenth of the toll ten years ago. The death rate among dogs is down by the same percentage; the rate among cats and farm animals has been halved in the past decade. Yet rabies is still so serious a problem that each year at least 30,000 Americans who have been bitten take the 14-day series of vaccine injections. Last week the U.S. Public Health Service assembled its top virologists and epidemiologists, along with state and city veterinarians and teachers of preventive medicine, to bring one another up to date.

Why does rabies still loom so menacingly? Among wild animals it is increasing fast enough to raise the nation's overall total of cases steadily. A persistent mystery is just how the virus survives: since it invariably kills its victim, at least among the higher animals, it might be expected to die with him. But it may have another reservoir somewhere. Opossums and bats seem to have some tolerance for the virus. Rabies is spreading where opossums are spreading, and it is spreading among bats.

The ironic reason that so much remains to be learned about rabies, says Dr. Robert G. Scholtens of the PHS's Communicable Disease Center, is that Pasteur produced an apparently workable vaccine so fast. His success in 1885 stifled medical interest in investigation of the disease.

Rabbits & Duck Eggs. Pasteur's and later rabies vaccines are unique in being given after the victim has been infected. This is because the disease has an amazingly variable incubation period--from ten days to eight months in both man and dog. An infected animal is not literally "rabid" or dangerous until ten days before its inevitable death. If a rabid dog bites a child in the arm or leg, the virus will stay localized for weeks before it attacks his central nervous system. Doctors usually start daily injections of vaccine into abdominal muscle without delay. If the animal has been captured and is still alive and normal after ten days, its saliva was not infectious, and the injections are stopped. If the animal dies, all 14 injections are given. Although the long series of uncomfortable injections often turns out to have been an unnecessary precaution, it is better than living in an agony of doubt about the threat of an agonizing death.

Until recently all rabies vaccine was made much as Pasteur made it: by injecting the virus into the brains of rabbits. The vaccine that was later extracted contained rabbit-brain protein, and it was likely to set up painful local reactions. In some cases it caused paralysis or death. In 1957, Eli Lilly & Co. began marketing a vaccine made in fertilized duck eggs. Only the occasional person who is allergic to eggs will get a bad reaction from it. For dogs, a preventive vaccine made from live, though weakened, virus has proved effective. But it has been considered too risky for man.

Last week the C.D.C.'s Dr. Ernest Tierkel, known in the trade as "Mr. Rabies," reported promising results in tests with pre-exposure vaccination for people who run special risks--veterinarians, dog handlers and wildlife rangers. This protection program, Dr. Tierkel suggested, may be just the ticket for Peace Corps workers and other people going into areas where rabies is endemic, especially in Central and South America, home of the vampire bat.

Human-to-Human Serum. Dr. Tierkel also had good news for people who may be bitten by suspected rabid animals around the head and neck--from which the virus may reach the central nervous system before abdominal injections have time to build up protective antibody. Since 1954. these victims have been injected with antirabies serum from horses. This gives only short-lived, "passive" immunity, but it works fast. The trouble is that horse serum is almost as dangerous as the rabbit-brain product. Now, said Dr. Tierkel, veterinarians and others who have had a full course of vaccinations are being asked to take a booster shot of duck-egg vaccine. A month later, they donate a pint of blood. The gamma globulin fraction from the serum in these blood samples is rich in rabies antibody, and because it is from human serunr it should cause no bad reactions.

* Standing at left. Louis Pasteur.

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