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Fact Sheet N°99
Revised June 2001

Rabies

Rabies is a zoonotic viral disease which infects domestic and wild animals. It is transmitted to other animals and humans through close contacts with saliva from infected animals (ie. bites, scratches, licks on broken skin and mucous membranes). Once symptoms of the disease develop, rabies is fatal to both animals and humans.

The first symptoms of rabies are usually non-specific and suggest involvement of the respiratory, gastrointestinal and/or central nervous systems. In the acute stage, signs of hyperactivity (furious rabies) or paralysis (dumb rabies) predominate. In both furious and dumb rabies, paralysis eventually progresses to complete paralysis followed by coma and death in all cases, usually due to respiratory failure. Death occurs during the first seven days of illness without intensive care.

Incidence

Reliable data on rabies are scarce in many areas of the globe, making it difficult to assess its full impact on human and animal health. The annual number of deaths worldwide caused by rabies is estimated to be between 40 000 and as high as 70 000 if higher case estimates are used for densely populated countries in Africa and Asia where rabies is endemic. An estimated 10 million people receive post-exposure treatments each year after being exposed to rabies suspect animals.

Since 1990 rabies in wildlife has been eliminated in some Western European countries that have conducted oral vaccination campaigns. With the help of this technique rabies could eventually be totally eliminated from its terrestrial reservoirs in Western Europe. Oral vaccination programs for dogs have been or are in the process of being evaluated in a few developing countries where canine rabies is endemic. Dramatic decreases in human cases of rabies have also been reported during recent years in China, Thailand, Sri Lanka and Latin America following implementation of programmes for improved post-exposure treatment of humans and the vaccination of dogs.

Transmission

In developed countries rabies is present mainly in wild animal hosts, from which the disease spills over to domestic animals and humans. Recently bat rabies has emerged as an important epidemiologiic reservoir in some parts of the world (i.e. the Americas and Australia). In North America, most documented human rabies deaths occurred as a result of infection from the silver haired bat rabies virus variant and in Australia at least 2 human deaths have occurred from exposure to a previously unrecognized rabies virus. In contrast, in most countries of Africa, Asia and Latin America, dogs continue to be the main hosts and are responsible for most of the human rabies deaths that occur worldwide.

The most frequent way that humans become infected with rabies is through the bite of infected dogs and cats, wild carnivorous species like foxes, raccoons, skunks, jackals and wolves, and insectivorous and vampire bats. Cattle, horses, deer and other herbivores can become infected with rabies and although they could transmit the virus to other animals and man, this rarely occurs.

Post-exposure treatment

The most effective mechanism of protection against rabies is to wash and flush a wound or point of contact with soap and water, detergent or plain water, followed by the application of ethanol, tincture or aqueous solution of iodine. Anti-rabies vaccine should be given for Category II1 and III2 exposures as soon as possible according to WHO recognized regimens. Anti-rabies immunoglobulin should be applied for all Category III exposures and for Category II exposures in immunosuppressed patients. Suturing should be postponed, but if it is necessary immunoglobulin must first be applied. Where indicated, anti-tetanus treatment, antimicrobials and drugs should be administered to control infections other than rabies.

The use of highly purified horse immunoglobulins can provide at least a partial solution to the current problems of insufficient quantities and high cost of human immunoglobulin. Further details on pre- and post-exposure can be found in the reports of WHO consultations held in 1996 and 2000 respectively and available at www.who.int/emc-documents/rabies/whoemczoo966c.htm and www.who.int/emc-documents/rabies/whocdscsraph2005c.html. A slide set on WHO recommendations on pre and post exposure treatment can also be accessed and downloaded at: www.who.int/emc/diseases/zoo/slides.

In case of human exposure to animals that are suspected of having rabies, immediate attempts should be made to identify, capture or kill the animal involved. In case of a Category III exposure, post-exposure treatment should be started immediately and can be stopped if the animal is a dog or cat and remains healthy after 10 days. Tissue samples should be taken from dead animals and sent to competent laboratories for diagnosis. The responsible veterinary services should be notified and information obtained on the epidemiological situation in the area.

Vaccines and immunization

Neural tissue rabies vaccines, still widely used in developing countries, require daily injections over a period of 14 days, followed by booster shots. Highly purified and potent modern cell culture and embryonating egg vaccines were developed over three decades ago. Reduced vaccination schedules and routes for vaccine administration (particularly the intradermal route) have been successfully used in developing countries where the cost of the five dose intramuscular schedule is prohibitively expensive. In addition to the five-dose Essen regimen given on days 0, 3, 7, 14 and 28 in the deltoid muscles, the following reduced intradermal treatment regimens also fulfill WHO requirements:

The Red Cross 2-site ("2-2-2-0-1-1") and the "8-0-4-0-1-1" intradermal schedules have been evaluated and used extensively in some developing countries to replace nerve tissue vaccines where expensive intramuscular vaccination regimes are not an alternative. For more details please consult our web sites: www.who.int/emc-documents/rabies/whoemczoo966c.htm .Intradermal injections should be administered by staff well trained in this technique.

Rabies immunoglobulin

Rabies immunoglobulins is expensive and may be either in short supply or non-existent in most developing countries where canine rabies is endemic. However, rabies immunoglobulins should be administered in all Category III exposures and in Category II exposures that occur in immunosuppressed persons. Both purified equine rabies immunoglobulin and human immunoglobulin are used in developing countries. The full dose of rabies immunoglobulin, or as much as is anatomically feasible, should be administered into and around the wound site. Any remainder should be injected intramuscularly at a site distant from the vaccine administrative site.

If the dose of rabies immune globulin is too small to infiltrate all wounds, (as might be the case in a severely bitten child) the correct dosage of rabies immune globulin can be diluted in physiological buffered saline to insure more wound coverage.

Vaccination in immunosuppressed persons

Severely immunosuppressed patients may not develop an immunologic response after rabies vaccination. Therefore, prompt and appropriate wound care after an exposure is an essential step in preventing death. In addition, rabies immune globulin should be administered in all immunosuppressed patients experiencing Category II and Category III wounds.

Rabies in children

Where data are available, there is consistent evidence that between 30 - 60% of human cases of rabies occur in children under 15 years of age. The majority of these children are not treated because their exposures go unreported to parents or health officials. In order to reduce the mortality rate in children the following activities should be strengthened or initiated in countries where successful canine rabies vaccination or control programs have not been put in place: 1) Promote proper and immediate care of dog bite wounds; 2) Increase access to modern cell culture vaccines in vulnerable populations including pre-exposure vaccination in children living in regions where canine rabies is highly endemic; 3) Promote proper application of effective and economical rabies post-exposure treatment; 4) Prevent dog rabies through dog vaccination.

Conclusions

Prevention of human rabies must be a community effort involving both veterinary and public health officials. Rabies elimination programmes focused mainly on mass vaccination of dogs are largely justified by the future savings of discontinuing prevention programmes. However, until canine rabies is eliminated or at least well controlled, safer and more economical post-exposure treatments for humans are a desirable alternative to the use of nerve tissue vaccines, Pre-exposure vaccination has been widely and successfully used to prevent rabies in at risk populations in industrialized countries and should be promoted in children living in regions where canine rabies is highly endemic. If rabies is not eliminated, expenses related to prevention of the disease in both humans and animals are likely to increase dramatically in developing countries.

For further information, journalists can contact Office of the Spokesperson, WHO, Geneva. Telephone (+41 22) 791 2599; Fax (+41 22) 791 4858; Email: inf@who.int All WHO Press Releases, Fact Sheets and Features as well as other information on this subject can be obtained on Internet on the WHO home page http://www.who.int/

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