Rabies
Rabies is an outstanding example of a dangerous disease which could be controlled or eventually eradicated in this country but which is not under control because of failure to impose and thoroughly carry out uniform regulations. Here is an account of the disease and the control measures it demands.
Through its veterinary services, Federal, State, and private, the United States has been outstanding among the countries of the world in controlling and eradicating animal diseases and, generally speaking, has attained a freedom from infectious animal diseases second to none. There is one animal disease that is far too prevalent in this country, however, and that disease is rabies. The irony of the situation lies in the fact that rabies is controllable and even eradicable if present knowledge were applied. Outstanding livestock sanitarians and scientists visiting this country from abroad have from time to time expressed. Amazement at the prevalence of rabies in the United States—a country in which such great strides have been made in the control or eradication of foot-and-mouth disease, tuberculosis, brucellosis, and. other contagious diseases of animals.
Before entering into a discussion of the reasons for the prevalence of rabies in this country it would be well to discuss the known facts concerning the disease and methods for its control.
Rabies or hydrophobia is ages old; it was described several centuries before the beginning of the Christian era as a dread disease. Only in modern times, however, through the brilliant work of Pasteur and others following him, has exact information become available on the cause, transmission, and control of rabies.
The disease is primarily one of the dogs, although a wide variety of species are susceptible to infection, including man. Rabies has-been reported in the cat, cow, horse, mule, sheep, goat, hog, wolf, fox, coyote, hyena, skunk, monkey, deer, antelope, camel, bear, elk, polecat, bat, squirrel, hare, rabbit, rat, mouse, jackal, badger, marmot, wood-chuck, porcupine, weasel, hedgehog, gopher, raccoon, owl, hawk, chicken, pigeon, and stork. It is definitely recognized, however, that the chief disseminator of rabies is the dog and that when rabies is once controlled in this species it will cease to be of any great importance from an economic or public health standpoint. It should be recognized, however, that once the disease becomes established in a wild species, a serious situation develops, and strenuous efforts must be made to control it in the species affected.
The disease is caused by a filterable virus—a type of infective agent sometimes called an ultramicroscopic virus, capable of passing through certain filters that retain ordinary bacteria and not rendered visible by any of our present-day microscopes. The infective agent is found in the saliva of affected animals, and under natural conditions, as it exists in dogs, the disease is produced by the bite of a rabid animal or by contact with the saliva of a rabid animal. The bite makes a wound in which the virus in the saliva is deposited.
The period of incubation, that is, the time between exposure to infection and the first appearance of ’symptoms of the disease, invariable. It may be as short as 2 weeks or as long as many months. The majority of cases, however, develop within a 3-month period.
Every animal or person bitten does not necessarily develop the disease, and the percentage of fatalities has been variously estimated. According to Hog, the proportion of persons who ‘contract the disease after being bitten by rabid dogs and not treated is conservatively estimated at 15 percent. The percentage inconsiderably higher in man following bites by the wolf. From 35 to45 per cent of the dogs, 40 per cent of the horses, 36 per cent of the hogs, and 25 to 30 per cent of the cattle bitten by rabid animals contract the disease, making a general average of about 35 per cent for these animals. Whether an individual animal contracts the disease depends in part on the location and size of the wound, the amount of hemorrhage produced, and various other conditions. In general, the nearer the bite to the central nervous system and the deeper the wound, the greater is the danger of infection. In cases in which the hemorrhage resulting from the bite is profuse, there is possibility that the virus will be washed out of the wound. Also, exact information is not available on whether the virus of rabies inconstantly present in the saliva of a rabid animal. It may be variable in both quantity and virulence.
After being deposited in the wound, the virus remains latent furan extremely variable period of time, which depends on the size and depth of the wound as well as its location and the amount of virulent saliva introduced. Experiments have proved that the virus follows the course of the nerves to the spinal cord and along the latter to the brain before the symptoms appear. Garlic, who collected statistics from a large number of cases, found the period between the bite and the appearance of the first symptom to vary from 14 to 285 days.