Why Latin America is nearer elimination of rabies than Africa

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"World Rabies Day" is September 28th. Copyright: CC, Global Alliance for Rabies Control   
   
Rabies: a contagious and fatal viral disease of dogs and other mammals, transmissible through the saliva to humans and causing madness and convulsions. Rabies is fatal once symptoms appear.

Latin America is doing far better at managing, controlling and ultimately eliminating rabies from the region. Africa is failing to make the same gains and a rethink is required: can the lessons learned in Latin America be  applied or adapted to Africa?

At  the biennial RSTMH meeting “Challenges in Disease Elimination” held in Cambridge [September 12-16th, 2016], Katie Hampson [University of Glasgow] described the Pan American Health Organisation (PAHO)'s surveillance & management framework operating in Mexico and Brazil,  and devised to support the elimination of rabies in 25 PAHO countries. She also described the work of Tanzanian colleagues who have developed a “pragmatic approach to surveillance” for the African setting where resources are constrained.

Current situation of rabies control in Latin America vs Africa

The short answer is that in Latin America, PAHO, which exists to “strengthen national and local health systems and improve the health of the peoples of the Americas”, has concentrated on vaccinating the dog population against rabies and interrupting transmission. African countries have no similar regional support structure for their health ministries and rely on post-exposure prophylaxis (PEP)  of humans bitten by dogs, to achieve a form of control of rabies. PEP vaccination only saves lives if the bitten person has timely access to a well-stocked clinic, and the money to pay for the shots. In remote and rural areas, this can lead to grim choices: which child do you treat if you only have money for one?  We heard at the RSTMH of an African mother with several children bitten by the “family dog”, who having travelled a great distance to reach the vaccine, was then faced with that very choice.

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One medicine; in practice

The
‘One-medicine’ movement has been boosted by the launch of a new web site at http://www.onehealthinitiative.com.
It aims to promote the idea of ‘one
medicine’ throughout the world and provide information on this initiative for
the public, political and governmental leaders, news media, and all ‘One Health’
professionals, advocates, and supporters.

The concept of ‘one
medicine’ is now well established having been adopted by both the American
Veterinary Medical Association (AVMA) and the American Medical Association. It
seeks to enhance collaboration between veterinarians and physicians, and other
health professionals, to promote the health and well being of all species. More
recently, the health of the environment has been included in the ‘one medicine’
concept reflecting the facts that all three are interlinked. The term one medicine
was first used by the pioneering veterinary epidemiologist, Calvin Schwabe, who
sought to break down the barriers between human and veterinary medicine.
Professor Schwabe set up the Department of Epidemiology and Preventive Medicine
at the University of California, Davis, in 1966, which was the first veterinary epidemiology department in the world.
He developed his ideas from his experiences in researching into hydatid disease
and other parasitic zoonoses while he was teaching at the American University in Beirut.

The idea of ‘one
medicine’ sounds very worthy and laudable, but it is not always easy to
envisage how in practice to impact on the lives humans and animals and the
environment. If anyone wanted a really good example of how the ‘one
medicine’ approach can benefit all three, they would have done well to have
attended an excellent talk delivered by Dr Sarah Cleaveland on rabies control in
Africa, given at the British Veterinary Association Congress in London on Friday
26 September. Those of us who were fortunate to be there heard how the health of
livestock, wild animals and humans in the Serengeti are woven together in a
dynamic relationship, and how measures to control infectious diseases affect the
humans, livestock, wild animals and the environment. Dr Cleaveland has been
based at the veterinary school in Edinburgh, was awarded the Trevor Blackburn Award in recognition of her work on zoonotic,
livestock and wildlife diseases in East Africa and for her outstanding
contributions to animal and human health, wildlife conservation and animal
welfare in Africa and beyond. The talk covered the effects of
disease and its control in the Serengeti region of Tanzania, known to viewers of wildlife programmes as the site of spectacular wildebeest
migrations, followed by lions and other carnivores that live off them. Dr
Cleaveland spoke about the control of a number of zoonotic diseases such as
brucellosis, tuberculosis, and echinococcosis, but it was her account of the campaign
to control rabies which really showed the value of the ‘one medicine’ approach.
Rabies is a very serious problem in many parts of the world and it is
estimated that 55,000 people die from the disease each year. Most of the victims
are children, and poor children in remote areas are the most likely to die if
infected, because the cost of the post-exposure vaccine and time taken to reach
a clinic. We heard how epidemiological techniques were used to prove that dogs
were the reservoir host (and not the wild carnivores that were also affected),
and how a mass dog vaccination campaign that she directed and implemented, currently vaccinating
200,000 dogs annually, has prevented hundreds of human and animal rabies deaths.
We also learnt that one of the most difficult parts of the control programme was
persuading the Masai dog owners to wait in an orderly line to have their dogs
vaccinated, and that the commonest pet names for their dogs were ‘Osama’ and
‘Bush’. As well as saving at least 50 human lives saved each year, at a
fraction of the cost of post exposure vaccination, the measures have also
protected endangered wildlife species, such as the African wild dog.

We also learned how the wildebeest numbers, a dominant
feature of the ecology of the Serengeti, have grown since the control of
rinderpest in cattle in the 1960s, and that as reservoirs of malignant catarrhal
fever virus, the arrival of the wildebeest to the lush lowlands of the Serengeti
drives the Masai to take their herds, to higher more marginal grazing, which can
lead to environment problems from overgrazing.

A search of the CAB Abstracts database for information on
‘one medicine’ shows that not only is the concept helpful in improving the
lives of pastoralists in developing countries, but can also help deal with
global problems such as obesity and heart disease through the benefits of the
animal human bond.

Only 2 Days Left until World Rabies Day 2008!

Organisations around the world will be aiming to raise awareness and understanding about the importance of rabies prevention on the second annual World Rabies Day on 28 September.

The Alliance for Rabies Control (ARC) is leading World Rabies Day (WRD) initiative, which is sponsored by numerous human and animal health organizations worldwide too. Its aim is to raise awareness and understanding about the importance of rabies prevention, which kills 55,000 people each year, half of which are children under the age of 15 and mostly in Africa and Asia. Its principle objectives are also to enhance education and resources in order to prevent and stop the disease by combating it in animals. Experience has shown that rabies can be successfully eradicated if control programmes are well defined, resourced and implemented, but around 8000 cases are still observed in Europe alone every year, of which about 60% in wildlife and 40% in domestic animals and also some human cases.

During the successful inaugural World Rabies Day 2007, over seventy countries participated through activities such as prevention messages for the public, dog vaccination campaigns, lectures and educational seminars, press conferences, museum and zoo exhibits, parades, festivals, marches, runs or dog walks. This year’s campaign shows promise for participation of even greater number of countries and organizations across the globe.

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The butterfly effect: diclofenac, vultures and rabies.

The idea that the flap of a butterfly wing in China could cause a tornado in Texas comes from the concept of  ‘sensitive dependence on initial conditions’ as part of the chaos theory, and has inspired short stories, poems and films, and the term ‘Butterfly Effect’ has entered the language. Assigning cause and effect in science is notoriously difficult, but there is growing evidence that there is a link between an anti-inflammatory drug for cattle, the demise of the Asian vulture. and the death of children from rabies in India.

The depressing story of the collapse of vulture populations in India began in the 1990s when it was noticed that the numbers of vultures, a common site in rural India, were suddenly in decline. The loss of vultures had a devastating ecological effect, as well as a social impact on the Indian Zoroastrian Parsi community, who traditionally use vultures to dispose of human corpses in "sky burials", and had to find alternative ways to dispose of their dead. The cause of the decline was a puzzle for scientists. New or emerging diseases such as West Nile were considered as a possibility, as bird populations in other parts of the world had been devastated by spreading viral diseases. 

Vultures have performed a vital role in clearing up the rotting carcasses of animals. I can remember on my first trip to India in 1983, stopping on the road from Dehli to Agra to take photographs of 50 or more griffon vultures gathered around a stinking pit of bones and carcasses. The driver was surprised at the request to stop to see the vultures – a common sight to him, and didn’t realise that then the time the largest raptor I was used to seeing in southern England was the sparrow hawk.

The culprit responsible for the vulture’s problems seems to be a drug residue in the carcases on which they feed. Diclofenac (2-(2,6-dichloranilino) phenylacetic acid) is a non-steroidal anti-inflammatory agent, which has analgesic as well as anti-inflammatory properties. Looking on the CAB Abstracts Database it can be seen that diclofenac has been used in cattle to treat a number of different conditions including arthritis, mastitis, repeat breeding, babesiosis, theileriosis, parotitis, downer cow, radial paralysis, mastitis, and emphysema. Often it is used in conjunction with other drugs for supportive therapy. Because of the ecological problems that the residues of the drug have caused the manufacture of diclofenac for veterinary purposes has been banned in Nepal, India and Pakistan. It is, however, still available as a human drug, and is still cheaper than a safer substitute meloxicam. 

The severe effects are due to a number of factors that have come together. Vultures are more susceptible to the toxic affects of diclofenac, in particular acute kidney failure, than are other species. In India, cattle do not usually go into the human food chain and the dead ones would be left for the scavengers. Another unfortunate factor is that diclofenac has a particularly long elimination half life in cattle (30.5 +/- 9.4 hrs compared with 1.1 hours in humans), and would therefore more likely to form residues in the carcase. Even with restrictions on the use of diclofenac, vulture populations will not recover quickly. Vulture populations have been reduced by more than 99% and several species of Gyps are now on the endangered species list. Gyps vultures take several years to reach sexual maturity, and a pair produces only one or two young every one or two years, so it could take decades before their populations recover. Concern for vultures has also spread to Africa where diclofenac is now being manufactured.

As nature abhors a vacuum, the gap left by the vultures has provided other scavengers with a feast. The opportunity has been exploited by stray and feral dogs, usually the pariah dogs, whose numbers have grown.  With the growth in the numbers of dogs the risk of rabies has also grown.. Dogs are the main vector of human rabies in India.  It is estimated that about 10,000 people die each year from rabies in India, and most of these are in the rural areas and a large proportion are children. The cost of post exposure treatment for the poor is also a contributing factor to the high death rate.