Rabies: Signs and Symptoms in Animals and Human Beings

Rabies is a disease, which man acquires from vertebrate animals. The disease is caused by a virus infecting the nervous tissue. Rabies causes 100% mortality if the human beings bitten by rabid animal and are not adequately vaccinated. Rabies is a disease of antiquity, having been known to mankind probably earlier than 2000 BC. Clinically, in both animals and man, rabies can manifest either in the form of hyperactivity (furious rabies) or paralysis (paralytic or dumb rabies). Human beings if not given prophylactic vaccination after animal bite always develop furious type rabies, whereas around 25% of dogs develop furious type rabies. Excessive salivation and lacrimation may also be present in affected animals and human beings. Hydrophobia (fear from water) may also be present in majority of the cases. No drugs work after the development of symptoms of rabies and patients lapse into coma and die. Millions of people are treated worldwide with post bite prophylactic vaccination for suspected rabid dog bites, every year.

The great Louis Pasteur was the first authority to make rabies vaccine by inactivating rabies virus obtained from the spinal cord of infected rabbit. The 'old stock vaccine' is made from the monkey's nervous tissue and 12 to 14 injections of this vaccine are required for 100% protection. Almost half of people vaccinated with 'old stock vaccine' may have appreciable local side effects and only 5 in 10,000 may have serious side effects. The latest anti-rabies vaccines have minimal side effects. The Purified Chick Embryo Cell (PCEC) and Human Diploid Cell (HDC) vaccines give 100% protection not only to those who are bitten by rabid dogs but also to those who work with rabies virus and handle reservoir animals. All vaccines are easily available worldwide at reasonable rates. Neurological complications may develop in persons vaccinated with 'old stock vaccine'.

Incubation Period: The incubation period of rabies disease is usually between one and two months. In extreme cases incubation period may be a few days or rarely, even years. The site of the bite is indicative in determining the length of incubation period. Infants and children have a shorter incubation period than adults. Restlessness, agitation, excitation, confusion, muscle spasms, hallucinations, thought disorders and hydrophobia are common signs of possibility of development of rabies in person infected with rabies virus.

Diagnosis: The diagnosis of rabies in animals is made by microscopic examination of stained brain smears or histological sections for Negri bodies. The biological test for rabies is intra-cerebral inoculation of mice with the nervous tissue squash of animals or body secretions of infected human beings and isolation of virus from inoculated mice after an incubation period of 1-2 weeks. In human beings the rabies virus can directly be isolated from saliva, urine and cerebrospinal fluid, and revealed by electron microscopic study.