Rabies is a potentially deadly virus caused by the lyssaviruses in the Rhabdovirus family. Rabies is an acute viral encephalomyelitis that principally affects carnivores and any mammals. Rabies is not restricted to any particular country but is a world-wide disease and as such, countries have imposed strict quarantine policies/controls when exporting animals or importing animals.
In North America and Europe, canine rabies has been more or less eradicated because of programs put into place to first eliminate rabies from wildlife. One successful program is dropping of fresh meat loaded with ant-rabies vaccine from helicopters to remote places where rabid carrying animals are located. These animals consume the meat and eventually the animals build up a resistance to rabies.
Rabies is usually transmitted by the bite of an infected rabid animal. When the rabid animal bites, the animal introduces rabies infected saliva into the tissues of the bitten animal. Another form of transmission is where saliva from the rabid animals enters into a wound or contusion of another animal.
This transmission electron micrograph (TEM) revealed the presence of numerous dark, bullet-shaped rabies virions within an infected
tissue sample. Courtsey CDC – National Center for Infectious Diseases - Rabies
The incubation period can be from 21 to 80 days after being infected, however depending on the disposition of the animal bitten it can be either shorter or longer.
Since the disease affects the nervous system, the virus travels along the peripheral nerves to the spinal cord and moves towards the brain. The rabies virus is not spread by blood.
Rabid animals usually show signs of Central Nervous System (CNS) behavior problems leading to paralysis. Behavior problems include sudden anorexia, signs of apprehension or nervousness, irritability, and hyper excitability (including priapism). The animal may seek solitude. Normal docile animal may suddenly become vicious. Rabid wild animals may become fearless of humans, and nocturnal animals may be seen wandering about during the daytime.
Clinically, rabies can be divided into three stages:
This stage is when the rabid animal shows signs of minimal CNS symptoms and rises rapidly to where the animal becomes paralyzed and eventually expires. This period last from one to two days.
Furious Form Stage:
Also known as the "mad dog stage". At this stage the rabid animal is not paralyzed but shows signs of very aggressive behavior. Any noise or attraction makes the animal vicious, showing it's teeth and exhibiting fearlessness. In this stage they can attack other animals and human beings.
This photograph shows a canine suspected of being rabid that had been exhibiting signs of restlessness, and overall uncharacteristic aggressive behavior, which are two symptoms of rabies. Other symptoms of rabies in pets may include impaired walking, eating and drinking.
Courtsey CDC – National Center for Infectious Diseases - Rabies
Paralytic Form Stage:
From the Furious Stage the rabid animal migrates into the Paralytic Stage. As the virus spreads rapidly through out the CNS, paralysis becomes imminent. The first signs of paralysis occurs where the the throat and masseter muscles become debilitated. As hours go by, the animal becomes completely paralyzed, goes into a coma and succumbs to death.
Whenever rabies is suspected in an animal, blood work is taken and sent to a qualified laboratory where analysis is done to confirm the diagnosis of rabies. If the lab analysis is positive, then the proper health authorities are notified and procedures which are in place for rabies are carried out.
In the pet industry, rabies is controlled by anti-vaccines given by veterinarians. In some countries, the anti rabies vaccine is given out free of charge or for a nominal fee.