Rabies also known as Hydrophobia (fear of water) is a highly fatal virus infection of the nervous system caused by Rhabdovirus. It is spread world wide and affects all warm blooded animals including man and other domestic and wild animals except birds. It is transmitted when infected animals bite other animals and contaminate the bitten wounds with the saliva containing the virus. The disease manifests by irritation of the brain resulting into over excitement, mania and attack complex by the infected animals. In Kenya, the disease is more serious in rural than urban areas. It is common in the rural areas because most of the rural people are not aware of the dangers associated with the disease. It is occurrence in the rural areas is also attributed to the social attachment to the local dogs kept and regarded as pets by the youth. The dog is also regarded as a source of security in the rural areas and is present almost in every homestead. Because of the fact that most of the rural people are not aware about the hazards of the disease, they are not bothered to vaccinate their dogs to protect them against rabies.

The virus is excreted through the saliva of an infected animal and the route of transmission is the contamination of fresh wounds with infected saliva usually produced after the bite of the rabid animal. It can also be transmitted through inhalation and ingestion of the causative agent. The virus spreads from the site of the bite to the brain, other nerves of the body and salivary glands thus causing the clinical signs several weeks or months later. The dog is regarded as the main transmitter of the disease but other domestic animals such as cats, cattle, sheep and goats can as well transmit the disease among themselves as well as to human.

Following the bite of a rabid animal, the incubation period takes a few days to several months. In cattle, incubation period takes three weeks but may also vary between 2 weeks to several months as well. The disease can last from as short as two days to about a week after the onset of the clinical signs. The first sign is change of behavior which may take two to three days in dogs. The next stage is the excitement stage whereby the animals would display the typical signs of rabies such as restlessness, aggressiveness and voice changes. Depending on the species of the infected animal, the voice changes may include howling, roaring and bleating. Infected people would be heard barking like dogs while for dogs, they would make unprovoked attacks on other animals or objects. This stage is referred to as 'furious' rabies and lasts for about four days. This is the most dangerous stage of transmitting the disease to human by dogs. The infected animals then develop paralysis from the rear limps and would refuse to eat or drink while profusely salivating. The paralysis phase is often referred to as 'dumb' rabies due to the dominant clinical feature. In this form cattle would show uncoordinated gait and the hind quarters would show periodic collapse. The tail would become flaccid. There would be decreased sensation evident over the hind quarters followed by tenesmus and paralysis of the anus. The animals become unable to bellow then develop total recumbence. Death then quickly follows.

Presence of a carnivore showing sings of nervous disturbance should be suspected of the occurrence of rabies in a given locality. However, histological analysis of brain tissue would reveal the presence of Negri-bodies in the cytoplasm of the nerve cells of the brain.