Rabies is a viral disease that affects the dog's brain and spinal cord, where it causes fatal infalmmation. The disease can afflict any warm-blooded animal and humans. The virus is present in the saliva of infected animals, often racoons, foxes, skunks, and bats, and is usually transmitted through bite wounds. Rabies can also be transmitted if the infected saliva contacts a fresh wound or the lining of the mouth or nose. Because rabies poses such grave danger to humans, any dog that is not protected by a current rabies vaccination and is exposed to a suspicious animal or bites a human, must be quarantined for six months or euthanized. Owners may be fined for having an unvaccinated pet. Rabies is nearly always fatal once symptoms appear, but it can be prevented almost 100% of the time when postexposure rabies vaccine and immunoglobulin are administered soon after a rabies exposure occurs.3
The striped skunk (Mephitis mephitis), the most common skunk in the United States, is one of the important species in perpetuating wildlife rabies in the central regions of the country. In mongoose rabies is six times more common than in dogs. Most frequent behaviors reported in rabid striped skunks appear during the day are entering dog pens and attacking pets. Rabid skunks often attack anything that moves with extreme fury and frequently roam during daylight hours, which is unusual behavior for this nocturnal animal. Foxes are important reservoirs of wildlife rabies, along with raccoons and coyotes. Vampire bats, which feed exclusively on blood, are a major rabies threat to people and animals in Mexico.2
Rabies is a self-limiting disease in most animals. This means that when they become infected with the virus, they die and theoretically, therefore, all susceptible wildlife in the area should die. When the area becomes repopulated with wildlife after an interval of a year or two, no rabies should occur. However, in practice this does not happen. Animals have been found to recover from both inapparent and over rabies infection. Dogs may excrete the rabies virus for more than six months, while appearing perfectly healthy. Vampire bats have been known to similarly infective after more than two years. Serial passaging from small rodents to foxes may alter the virulence of the virus. In some cases the virus does not alter and the animal survives and excrete the virus.4
The rabies virus belongs to the genus Lyssavirus in the family Rhabdoviridae and is among the small number of viruses that kill all of the individuals they infect. The rabies virus is not only a deadly menace but also a truly amazing feat of nature. This virus, shaped like a bullet, is extremely small (180 nanometers long and 75 nanometers across). If you stack rabies viruses one on top of the next, you would need more than a thousand of them to reach the thickness of a single human hair. It is simple, tiny, and increadibly powerful. The virus particles that infect the central nervous system modify the host's behavior, increasing aggression, interfering with swallowing, and creating a profound fear of water. When put together, a rabies infection leads to an aggressive host literally foaming at the mouth with virus. A host that lacks the capacity to drink or swallow further increases the probability of delivering a successful bite, a bite that gives this particular virus the ability to advance from one individual to the next.1
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Of the two main classes of symptoms, the first is "furious rabies," in which the dog shows a period of melancholy or depression, then irritation, and finally paralysis. The first period can be from a few hours to several days, and during this time the dog is cross and will change his position often, lose his appetite, and begin to lick, bite or swallow foreign objects. During this phase, the dog is wild and has impulses to run away. He may act fearless and bite everything in sight. If he is caged or confined, he will fight at the bars and possibly break teeth or fracture his jaw, with his bark becoming a peculiar howl. In the final stage, the dog's lower jaw becomes paralyzed and hangs down. He then walks with a stagger, and saliva drips from his mouth. About four to eight days after the onset of paralysis, the dog dies.
The second class of symptoms is referred to as "dumb rabies" and is characterized by the dog's walking in a bearlike manner with his head down. The lower jaw is paralyzed and the dog is unable to bite. It appears as if he has a bone caught in his throat. If a dog is bitten by a rabid animal, he probably can be saved if he is taken to a veterinarian for a series of injections. After the symptoms appear, however, no cure is possible. As is with other shots, an annual rabies inoculation is very important. In many areas, the administration of rabies vaccines for dogs is required by law.
- Nathan Wolfe. The Viral Storm
- C. Greene. Infectious Diseases Of The Dog And Cat.
- Rabies Information for Specific Groups (CDC)
- A hair of a dog. J.M. Dunlop