Posted by: lidcblog | June 6, 2012

Rabies – an ancient disease continues to claim thousands of lives every year, but there is hope on the horizon

Vaccination of a puppy in Sri Lanka, by Barbara HaesslerA few days ago a British woman died in a London hospital after contracting rabies while on holiday in South Asia (Woman with rabies dies at London hospital, BBC News England). Does it mean rabies is back? How worried should we be?

 

What is rabies all about?
Rabies, first recorded in the 23rd century B.C. in the Eshuma Code of Babylon, is a disease present on all continents apart from Antarctica. Any mammal can become infected and there is a risk of transmission to humans (hence it is a zoonotic disease). Rabies is caused by a virus belonging to the Lyssavirus genus, which varies in genotype (it is different in, say, dogs, foxes, or raccoons than it is in bats).

At a global level, particularly in Asia and Africa, the most common way of transmission to people is by exposure to saliva from rabid domestic dogs through bites, scratches or licks to broken skin or mucous membranes (moist skin surfaces, like the mouth or inner eyelid). However, rabies can also be transmitted by other animals such as bats (the main source of transmission in the United States), cats, raccoons, skunks and foxes. After infection, the virus penetrates the tissue and then travels along peripheral nerves to the central nervous system to reach the brain where it multiplies. Once it reaches the central nervous system, the infection is untreatable and in almost all cases fatal. With adequate medical care consisting of local treatment of the wound, administration of rabies immunoglobulin (if appropriate), and vaccination, the onset of rabies symptoms and death is 100% preventable.

To avoid exposure, contact with unknown animals in rabies endemic countries/ areas, in particular adult dogs and puppies, should be avoided. Moreover, before travelling abroad to an area with rabies, you should seek medical advice as to whether you need pre-exposure rabies vaccination. Such vaccination will not give you full protection, i.e. after being bitten you should first wash the wound thoroughly with soap and plenty of water and immediately seek medical advice. The WHO provides a general guide to post-exposure prophylaxis.

Without such treatment, rabies first causes non-specific initial symptoms followed by an acute stage that can be expressed as “furious rabies” with hyperactivity, anxiety, hydrophobia (fear of water), confusion, hypersalivation and hallucination or as “dumb rabies” with muscle weakness, loss of sensation and progressive paralysis. In any case, people eventually fall into a coma and die.

How to prevent rabies from spreading across national borders?
Some countries, including the United Kingdom, have been free of rabies for a long time. While some nations have never had rabies, others implemented extensive vaccination programmes in domestic and wild animals to become rabies free. Because rabies remains endemic in many other countries worldwide, there is a risk of re-introduction of the disease to the UK through animal movements.

Since 1922, the UK has been free of classical rabies contracted locally, but there were 25 human rabies cases between 1946 and now, of which 24 were contracted abroad and one most likely caused by a bite from an indigenous bat. Because it is an island, the UK is deemed extremely unlikely to have rabies re-introduced through wildlife. Furthermore, there are comprehensive legal requirements in place for domestic animals that prevent the introduction of rabies. Consequently, the largest risk for rabies infecting the UK animal population would be through illegal imports of animals.

Although rabies can be prevented by mass vaccination of animals, the disease constitutes a major public health burden in developing countries that do not have the technical and financial resources to control rabies in animal populations. Particularly in Asia and Africa, there are few programmes in place to control the disease in animal populations, especially domestic dogs. Moreover, access to appropriate treatment after exposure is often complicated by prohibitive prices, unavailability of vaccines, and lack of awareness in the population. Therefore, every year over 55,000 people die from rabies worldwide. The actual figure is most likely much higher, because many bites and cases are not diagnosed and/or reported. The total annual costs in Africa and Asia related to post-exposure treatment, dog vaccination and population control, surveillance and livestock losses were estimated to be US $583.5 million.

Will we ever be rabies free?
But why has rabies not been eradicated yet? The availability of safe and effective vaccines for animals and humans and other achievements such as modern surveillance designs, epidemiological expertise and laboratory capacity make it technically possible to prevent human rabies cases and eliminate canine rabies. However, lack of resources, in-country expertise and awareness; limited coordination, collaboration and integration of budgets across ministries; and prioritisation of other pathogens make rabies a neglected disease. Many ongoing initiatives at national and international level are raising rabies awareness, addressing knowledge gaps and promoting effective rabies control strategies. Continued international collaboration and interdisciplinary efforts involving international organisations, local governments, NGOs, research institutes, industry and communities are needed to contribute towards sustainable implementation of control programmes in endemic areas, securing political commitment and funding, awareness raising and development of a global control strategy.

The Royal Veterinary College is active in the fight against rabies
The Royal Veterinary College (RVC) has been involved in zoonotic and infectious disease research, consultancy and educational partnering exercises at national and regional levels. It is one of four partner colleges that form the Leverhulme Centre for Integrative Research on Agriculture and Health (LCIRAH) that investigates themes with agricultural and health components in an interdisciplinary way. One of the Centre’s objectives is to understand the emergence, introduction, spread and transmission of foodborne and zoonotic diseases in food systems.

Contributed by Dr Barbara Häsler, LCIRAH Postdoctoral Research Fellow, Veterinary Clinical Services, Veterinary Epidemiology and Public Health Group, Royal Veterinary College (RVC)

Further information and rabies distribution maps
Centres for Disease Control and Prevention
FAO EMPRES Global Animal Disease Information System (EMPRES-i)
Global Alliance for Rabies Control
Pan American Health Organization – Epidemiological Information System
Rabies Bulletin Europe
World Organisation for Animal Health rabies portal
World Rabies Day
World Society for the Protection of Animals “collars not cruelty” campaign

Expert Q&A on rabies: Dr Ron Behrens from London School of Hygiene & Tropical Medicine (LSHTM)

Expert Q&A: Dr Ron Behrens on rabies


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