Rabies Health Article

Rabies

A viral disease that is fatal in humans if not treated immediately. It typically spreads to humans from animals through a scratch or a bite and causes inflammation of the brain.

Although the vaccine first used in 1885 is widely used today, fatalities from rabies still occur. Most fatalities take place in Africa and Asia, but some also happen in the United States. Prevention of rabies in the United States can cost as high as $ 1 billion per year.

From animal to human

While many animal diseases cannot be passed from animal to humans, rabies can, and since ancient times it has been known as an easy traveler from one species to the next. The very name rabies, Latin for "rage" or "madness," suggests the fear early men and women must have had for the disease. For centuries no treatment existed, and the disease was left to run a rapid course leading to death.

This changed in 1885, when French scientist Louis Pasteur saved the life of a nine-year-old boy who had been attacked by a rabid dog. Pasteur used a live virus vaccine made from spinal cords of infected rabbits. To be effective, the vaccine needed to be administered 14 to 21 times.

The vaccine has since been refined and improved many times. Currently, two rabies vaccines are used in the United States. Yet rabies continues to plague most underdeveloped parts of the world, particularly regions without access to health care.

Rabies is caused by a number of different viruses that vary depending on the geographic area and species. While the viruses are different, the disease they cause is singular in its course. The bullet-shaped virus is spread when it comes in contact with broken skin or a mucous membrane. Initially, the virus begins to reproduce itself in muscle cells near the place of first contact. At this point, within the first five days or so, treatment by vaccination has a high rate of success.

Once the rabies virus passes to the central nervous system, immunization is no longer effective. When it moves into the brain, it replicates itself there before finally moving to other tissues such as the heart, lungs, liver, and salivary glands. Symptoms appear when the virus reaches the spinal cord.

Since rabies symptoms for humans and animals mirror each other, sick animals are an excellent guide to understanding the disease. The common symptoms are muscle spasms, confusion, sensitivity to bright light, and fever. In addition, a fear of water and so-called foaming of the mouth, a symptom that occurs due to difficulty in swallowing and abnormally active salivation, are present. The incubation period from the time one is exposed to rabies to the time the disease develops is usually one to two months, but it can take as long as seven years for symptoms to make their appearance.

Dogs, cats, and bats

The likelihood that certain animals will contract rabies varies from one location to the next. Dogs are one example. In areas where public health efforts to control rabies have been aggressive, dogs make up less than 5% of rabies cases in animals. These areas include the United States, most European countries, and Canada. However, dogs are the most common source of rabies in many countries. They make up at least 90% of reported cases of rabies in the developing countries of Africa, Asia, and many parts of Latin America. In these countries, public health efforts to control rabies have not been as aggressive. Other key carriers of rabies include the fox in Europe and Canada, the jackal in Africa, and the vampire bat in Latin America.

In the United States, raccoons comprised 60% of all reported rabies cases. A total number of 4,311 rabid raccoons was reported in 1992. The high number of these cases suggests an animal epidemic, or epizootic. The epizootic began when diseased raccoons were carried further south from Virginia and West Virginia. Since then, rabies in raccoons has spread up the eastern seaboard of the United States. Concentrations of animals with rabies include coyotes in southern Texas, skunks in California and in south and north central states, and gray foxes in southeastern Arizona. Bats throughout the United States also develop rabies. When rabies first enters a species, large numbers of animals die. When it has been exposed for a long period of time, the species adapts, and smaller numbers of animals die.