Rabies

Epidemiology of Infectious Diseases: Rabies

Causal agent
Rabies virus - a rhabdovirus of the genus Lyssavirus

Common clinical features

  • Onset of symptoms often starts with apprehension, headache, fever, malaise, sensory changes depending on site of bite1.
  • Excitability and Aerophobia.
  • The disease progresses to paresis or paralysis; spasms of swallowing muscles leads to hydrophobia; delirium and convulsions.
  • Death is often due to respiratory paralysis.

Epidemiology

  • Worldwide - with an estimated 65,000 - 87,000 deaths per year (mostly in developing countries, particularly Asia and Africa)1.
  • No case of indigenous human rabies from animals other than bats has been reported in the United Kingdom since 19022.
  • In the UK rabies has been eliminated form the animal population.

Reservoir
Wild and domestic animals, including dogs, foxes, coyotes, wolves, skunks and raccoons. 

In developing countries dogs remain the principal reservoir.

Mode of transmission

  • Transmitted to animals and humans through close contact with saliva from an infected animal (bites, scratches, through broken skin and mucous membranes).
  • No person to person spread demonstrated.
  • Airborne transmission - uncommon
  • Organ transplants e.g. cornea (rare)

Incubation period
Usually 3-12 weeks,  with a range of 4 days to 19 years.
In 93-99% of patients, the onset is within one year of exposure1.

Period of Communicability
Dogs and cats  - from 3-7 days before the onset of clinical symptoms, and throughout the course of disease. 

Prevention and control
Post exposure immunisation

There are currently two licensed rabies vaccines in the UK:

  1. Rabies human diploid cell vaccine (HDCV)
  2. Purified chick embryo cell rabies vaccine (PCEC).

In the UK pre-exposure immunisation with rabies vaccine is recommended for2.

  • Laboratory workers handling the virus.
  • Persons who, in the course of their work regularly handle imported animals.
  • Veterinary and technical staff (SVS); the Department of the Environment, Food and Rural Affairs (DEFRA), the Scottish Executive Environment and Rural Affairs Department (SEERAD); the Welsh Assembly Government, Environment Planning and Countryside Department (WAG EPCD) and the Department of Agriculture and Rural Development, for Northern Ireland (DARD NI).
  • Inspectors appointed by local authorities under the Animal Health Act (1981).
  • People who regularly handle bats in the UK.
  • Overseas workers who by nature of their work are at risk of contact with rapid animals.
  • Health workers who are about to be exposed to a patient with suspected or confirmed rabies.
  • Some Travellers - those living or travelling for more than 1 months to rabies enzootic areas.

Post Exposure Management
Post -exposure management normally consists of wound treatment and risk assessment for appropriate immunisation2.

Prevention
Dog registration, immunisation and euthanasia of ownerless dogs in endemic countries1.
Surveillance for rabies in animals.
Quarantine animal known to have bitten a person in endemic area.

References

  1. Heymann D L, editor, Control of Communicable Disease Manual. 18th ed. American Public Health Association; 2004.
     
  2. Salisbury DM, Begg NT.  Immunisation against infectious disease (The green Book). London: HMSO, 1996. Available at http://www.dh.gov.uk/assetRoot/04/07/29/84/04072984.pdf

© CM Kirwan 2006