Berton Roueche - The Medical Detectives Volume I

Dr. Taylor's letter was dated October 19, 1953. Little more than two years later, on February 1, 1956, a news story authorized by the New Mexico State Department of Public Health appeared in the Santa Fe New Mexican under a six-column headline reading, "CARLSBAD CAVE BATS INFECTED WITH RABIES."

"Rabies," it began, "has been discovered among the millions of bats at Carlsbad Caverns. It was a rabies epidemic which caused the death of hundreds of the Caverns bats in August and September of last year." The account continued:

Last Aug. 20, officials of the National Park Service at Carlsbad noticed dead and dying bats in increasing numbers. They were found on the floor of the caverns and in its entrance. Ranchers in the area also found dead bats. At that time it was thought that extensive insecticide spraying might have caused the deaths during the 10-day epidemic. But tests by the U. S. Public Health Service found no evidence of this. Instead, tests were begun to see if rabies had caused the deaths.

Lt. Col. Kennet Burns, chief of the veterinary virus laboratory at Ft. Sam Houston, Tex., collected specimens of dead and dying bats for examination while the epidemic was going on. Virus examinations by Burns revealed the presence of rabies in more than 50 per cent of the specimens, the department said. In addition, blood samples from a large number of live bats collected in flight at the caverns after the epidemic showed the presence of antibodies against rabies, indicating that many of the bats had been exposed to the disease some time in the past. . . .

The story also stated that although no human being had ever been known to be bitten by a bat while visiting the caverns, the health authorities had warned people against touching any of the creatures they might find dead or dying there.

Rabies is one of around sixty human diseases now known, or confidently supposed, to be of viral origin. Its causative agent is thus a member of the most mysterious form of life on earth. About all that can be said of the viruses is that they are supremely small (some are only just within the reach of an electron microscope), infinitely numerous (not even the bacteria are more ubiquitous), and almost incomparably specialized. All viruses are obligate intracellular parasites. They share with the rickettsiae the otherwise unique distinction of being unable to grow or reproduce outside the protoplasmic tissue of a living host. In general, the severity of a viral invasion reflects the functional importance of the particular cells to which the invaders are drawn. The virus of rabies is a neurotropic virus. Like the viruses of poliomyelitis and the several encephalitides, it has a special affinity for the cells of the central nervous system. It has, however, little else in common with any other virus. Its range, for one thing, is extraordinarily wide. Unlike the great majority of viruses (including the agents of smallpox, measles, yellow fever, poliomyelitis, infectious hepatitis, and the common cold), which can find in nature fewer than half a dozen satisfactory habitats, it is able to exist comfortably and abundantly proliferate in any warm-blooded animal. Its means of transmission is also peculiarly its own. Most viruses insinuate themselves into host through either the respiratory passage or the gastrointestinal tract. A few are conveyed by bloodsucking insects. The rabies virus enters by way of a bite contaminated with the saliva of one of its victims. In this respect, it might seem to resemble the various mosquito-borne viruses, but the resemblance is merely apparent. The latter are transmitted in the natural course of the carrier's search for food. There is nothing natural about the transfer of the rabies virus. It wrings collaboration from its carrier hosts by torturing them into a homicidal fury. The incubation period of rabies (or the interval between the implantation of the organism und its establishment in the brain) is largely determined by the depth of the wound, its proximity to the brain, and the size of the original viral colony. This period, though disconcertingly variable, is seldom shorter than fifteen days and almost never longer than a year. But whether the virus reaches its destination in days or weeks or months, the result is inevitably the same. Rabies, in man, is a fatal disease.

The symptomatology of rabies is essentially the same in all susceptible animals. There are only superficial differences. The onset of the disease is generally mild and always indistinct. In man (and, insofar as can be determined, most comparably complicated animals), its earliest manifestations are those of any infection—a little fever, a dull headache, a scratchy throat, occasional nausea. This phase frequently lasts for two or three days, and sometimes even four, and is followed by a tingling pain at the site of the wound—the first diagnostically significant indication of rabies. Its grip, already fixed beyond release, then suddenly tightens. The muscles stiffen, the nerves tense, and the mind begins to fray with temper and apprehension. Anxiety quickens into fear. There is a vivid sense of approaching doom, a certainty of death. "A [rabid] patient weighed down with terror often becomes maniacal," D. L. Harris, medical director of the Pasteur Clinic in St. Louis, noted in a recent clinical study. "An excessive flow of thick tenacious saliva pours over his face and neck and becomes smeared on his hands and clothes and over the bedding and floor. These periods of rage are followed by moments of calm in which [he] usually shows anxiety for the safety of those around him and warns them of the approach of another crisis. Hyperesthesia of the skin to changes of temperature, and especially to currents of air, and increased sensitiveness to sound and light mark the progress of cerebral irritation. Convulsions are brought on by the least irritation and by the slightest current of air. . . the breath comes in spasms, dyspnea is extreme, and there are epileptiform seizures or tetanic rigidity. Hydrophobia is rarely absent. . . . When the patient [attempts to drink], there is an immediate viselike contraction of the muscles of deglutition with an excruciatingly painful spasm of the glottis and the pharynx. The body trembles with convulsive movements, the jaws are clenched, respiration is impossible. . . . After several attempts to drink, the pain is so terrible that despite intense thirst [the patient] cannot be induced to try to swallow liquids, and the sight of water or mention of the word brings on an attack. As a rule, death occurs after two or three days from cardiac or respiratory failure."

Although all highly developed animals are equally responsive to its gothic embrace, the rabies virus has its favored circle of hosts. It is naturally most inclined to frequent those best equipped to further its spread. This largely confines its normal range to the more prolific and short-tempered carnivores, a group that includes the fox, the wolf, the coyote, the jackal, the skunk, the mongoose, the cat, and the dog. Of these, the last, for reasons still obscure, has always been its most consistently conspicuous victim. The dog is also the animal in which its depredations were first recognized as those of a specific disease. Just when that occurred is uncertain. An illusion in the Iliad to "canine madness" has persuaded many medical historians that rabies may have been known to the Mediterranean world as early as the tenth century before Christ, and most believe, on the basis of rather stronger internal evidence, that the fifth-century Greek philosopher Democritus, who is chiefly remembered as a pioneer atomic theoretician and the teacher of Hippocrates, was probably conscious of its existence. The first explicit reference to rabies of which there is any record was set down by Aristotle, around 335 B.C., in his Historia Animalium.