Rabies

Rabies is caused by a rhabdovirus which infects the central nervous tissue and salivary glands of a wide range of mammals, and is usually conveyed, by saliva, through bites or licks on abrasions or on intact mucous membranes. Man is most frequently infected from dogs. In Europe the maintenance host is the fox and in recent years the zoonosis has spread from Poland westwards through Germany and France.

The incubation period, during which the virus is spreading centripetally along axons to the brain, varies in man from a minimum of 9 days to many months but is usually between 4 and 8 weeks. Severe bites, especially on head or neck are associated with short incubation period.

Louis Pasteur was the founder of the science of microbiology, proved the germ theory of disease, invented the process of pasteurization, and developed vaccines for several diseases, including rabies. Louis Pasteur spent his life working on the causes of various diseases—including septicemia, cholera, diphtheria, tuberculosis, and smallpox—and their prevention by means of vaccination. He is best known for his investigations concerning the prevention of Rabies. Pasteur developed an attenuated form of the virus that could be used for inoculation. In July 6, 1885, with the help of vaccine developed by him , the first human victim of active rabies was saved.

Clinical Features

Only a proportion of people bitten by rabid animal develop the disease, but once menifest it is almost always fatal. At the onset there may be fever and paraesthesia at athe sit of the bite. Prodromal period of 1 to 10 days during which the patient is increasingly anxious, leads to characteristic fear of water, “Hydrophobia”. Although the patient is thirsty attempts to drink water lead to violent contraction of muscles of diaphragm and other inspiratory muscles and thereafter even the sight or sound of water may provoke distressing spasms and attacks of panic. Delusions, hallucination may develop with spitting biting and mania. Cranial nerve lesions develop with terminal hyperpyrexia. Death occurs within a week of the onset of symptoms. In some ascending paralysis is seen without mental excitment, and these patients servive on average 12 days.

Clinical Features

Only a proportion of people bitten by rabid animal develop the disease, but once menifest it is almost always fatal. At the onset there may be fever and paraesthesia at athe sit of the bite. Prodromal period of 1 to 10 days during which the patient is increasingly anxious, leads to characteristic fear of water, “Hydrophobia”. Although the patient is thirsty attempts to drink water lead to violent contraction of muscles of diaphragm and other inspiratory muscles and thereafter even the sight or sound of water may provoke distressing spasms and attacks of panic. Delusions, hallucination may develop with spitting biting and mania. Cranial nerve lesions develop with terminal hyperpyrexia. Death occurs within a week of the onset of symptoms. In some ascending paralysis is seen without mental excitment, and these patients servive on average 12 days.

Investigation

Diagmnosis is usually on clinical grounds.

Immunofluoroscent techneques can detect antigen in the corneal smear impression and skin biopsies.

Management

Only a few patients with rabies have survived, and all of them had received some form of prophylaxis and needed intensive care to control respiratory and cardiaac failure. Once symptoms appear only palliative measures cn be taken.

Prevention

Pre-exposure prophylaxis is a must for those at a risk with antirabies vaccination.

Post-exposure prophylaxis

• Thorough cleaning of the wound with detergents or soap.
• Damaged tissue to be excised and wound left unsutured.
• Antirabies vaccine: The safest vaccine is the Human Diploid Cell Strain Vaccine. 1.0 ml given in the deltoid region days 0,3,7,14,30,90
• Human rabies Immunoglobulin 20 I.U. / Kg bwt. Half of the dose is infiltrated around the wound and the remaining half is given I.M. Hyperimmune animal serum 40 I.U. / Kg bwt.may also be used.

Rabies Vaccination

Rabies Transmission by Oral and Other Non-bite Routes

Rabies in Animals