Rabies

• What is Rabies
• Statistics on Rabies
• Risk Factors for Rabies
• Progression of Rabies
• Symptoms of Rabies
• Clinical Examination of Rabies
• How is Rabies Diagnosed?
• Prognosis of Rabies
• How is Rabies Treated?
• Rabies References

What is Rabies

Rabies is a viral disease of the central nervous system (CNS); it is one of the oldest and most feared diseases reported in medical literature. Incidence of rabies is widespread throughout the world.

Statistics on Rabies

Human rabies has been reported worldwide except for Australia, New Zealand and the Antarctic.

There are an estimated 15,000 cases of rabies worldwide each year.

Risk Factors for Rabies

Being in contact with an infected dog, namely recieving a bite from said dog, is the main risk factor in contracting Rabies. Worldwide, dogs still pose a significant risk for transmitting rabies, however. Bats, skunks, raccoons, foxes and other animals can also be sources of rabies virus.

Progression of Rabies

Rabies occurs in 2 main epidemiological settings:

1. Urban rabies: which is most commonly transmitted to humans through rabid dogs and sometimes cats; and
2. Sylvan (wild) rabies: maintained in the wild by a number of animal reservoirs including foxes, skunks, jackals, mongooses and bats.

The disease is usually transmitted through animal bites, however, bites leading to rabies varies from 10% on the legs to 80% on the head.

Once the virus has entered the body, it replicates in the muscle cells near the entry wound. It then penetrates the nerve endings and travels in the oxoplasm to the spinal cord and brain. In the central nervos system, the virus again proliferates before spreading to the salivary glands, lungs, kidneys and other organs via the autonomic nerves.

How is Rabies Diagnosed?

Rabies antigens can be detected by fluorescent antibody from corneal impressions or in salivary secretions. The biting animal should be diagnosed pathologically.

Prognosis of Rabies

An established infection of rabies in invariably fatal with death occuring in 10-14 days. There have only been 2 reported cases of survival from clinical rabies.

How is Rabies Treated?

Treatment is symptomatic as death is virtually inevitable. The patient should be nursed in a quiet, darkened room. Nutritional, respiratory and cardiovascular support may be necessary. Morphine, diazepam and chlorpromazine can be used in excitable patients.

The disease can be prevented using HDCV (human diploid cell vaccine).

Pre-exposure prophylaxis is given to individuals at a high risk of contracting the disease (e.g. lab workers, animal handlers and vets). HDCV 1.0mL deep subcutaneously or intramuscularly is given twice, 4 weeks apart. Another dose is given 12 months after that and then every 1-3 years depending on the risk of exposure.

Postexposure prophylaxis consists of 5 one mL doses given intramuscularly at days 0, 3, 7, 14 and 28. The wound should be cleaned, debrided and left open. Human rabies immunoglobulin should be given immediately with half injected around the area of the wound and half given intramuscularly (20IU/kg).

Domestic animals should also be vaccinated if there is any risk of rabies in the country.

Rabies References

1. Anderson LJ, Nicholson KG, Tauxe RV, Winkler WG: Human rabies in the United States, 1960 to 1979: epidemiology, diagnosis, and prevention. Ann Intern Med 1984 May; 100(5): 728-35.
2. eMEDICINE.
3. Kumar P, Clark M. Clinical Medicine. Fourth Ed. WB Saunders, 2002.
4. MEDLINE Plus.