Monday 26 August 2019

Rabies in dogs and humans can be easily prevented

People in Bangladesh with dogs. Pic: WSPA
People in Bangladesh with dogs. Pic: WSPA

Pete Wedderburn

AS YOU read this, people on the other side of the world are dying of a terrible disease: rabies. The disease kills over 55000 people every year, mostly children in Asia and Africa. Yet it can easily be prevented in both humans and animals.

This Friday - September 28th - is World Rabies Day, an initiative of the Global Alliance for Rabies Control. Rabies is a disease that should not kill people in the 21st century: the aim of those working in the field is to eradicate human rabies in the next fifteen years.

The rabies virus is like a submicroscopic version of an alien from a science fiction horror movie. The disease-causing agent multiplies in the brain and salivary glands of an infected dog, causing changes in the brain that make the animal fiercely aggressive, biting any living creatures within range. A bite from a rabid dog introduces saliva, teeming with infectious viral particles, into the body of the victim. The rabies virus then tracks up through the nervous system settling into into the brain and salivary glands, and the cycle is complete.

The disease has a long incubation period: it can take months for the virus to move from the site of the bite to the brain. People usually develop rabies within weeks, but it can take over a year for signs to develop.

The disease is bad enough in animals, causing episodes of bizarre behaviour and eventual death. For humans, there's the added issue of our consciousness of what is happening to us. People don't recover from rabies. By the time the rabies virus has entered the brain and signs of the disease have become apparent, it's too late. Death is inevitable. Infected humans suffer episodes of deranged, convulsive behaviour, interspersed by periods of normal, calm, rationality when they are fully aware of the unavoidable and unpleasant death that lies ahead.

Rabies used to be a big problem here in Ireland: towards the end of the nineteenth century, there were regular human deaths from the disease. Historian Sharon Clancy has gathered details of two real-life cases: they make compelling reading.

In December 1894, Denis Moloney, a man in his seventies who lived alone near Limerick, was standing in the boreen leading to his house when a local stray terrier jumped at him and bit him on the left hand. After a number of weeks his appetite gradually failed and he took to his bed, but he still did not wish to seek medical assistance and instead called on the services of a local 'charmer'. When a doctor was finally called in, hydrophobia (rabies) was diagnosed. He died a few days later, on 25 March 1895.

On 18 January 1896 Hanora Kenny, a 60year-old widow, was in her house at Fish Lane in Limerick when a cat jumped at her. The cat bit at the woman's arm, and she pulled it off by the scruff of its neck and held it while she screamed for help. Two men ran to her assistance; they killed the cat and took the woman to the local hospital. Sadly, the treatment was ineffective, and she gradually became worse and died three months later.

These days, people (such as vets working in Africa or Asia) who are at risk of being exposed to rabies can be vaccinated so that they're fully protected. And if members of the public in these countries are bitten by potentially rabid animals, they can be given post-exposure treatment.

It's only when this treatment isn't given that there's a serious risk of rabies, and death nearly always follows. It's not just local people who are risk: in May 2012, a woman died of rabies in a London hospital after being bitten by a dog during a visit to India. And 2009, a veterinary nurse who'd worked in an African animal sanctuary died of rabies in Northern Ireland, many months after returning home. Anybody who travels to one of the 150 countries around the world that harbour rabies needs to be aware of the risk.

Over a century ago, rabies was eradicated in Ireland through a combination of strict measures, including compulsory muzzling of dogs, rounding up of all strays, and a new vaccine that became available for dogs. Why is it, then, that rabies has not been solved in so much of Africa and Asia? There are two reasons: lack of resources and use of the wrong methods. Up until now, when there's a rabies outbreak, all dogs in the area have simply been culled, often by being shot. This has been shown to be ineffective.

There is a much better answer. mass dog vaccination. If 70 per cent of a local dog population is vaccinated, a barrier of healthy immune dogs is created, preventing the disease from spreading. Unable to spread between dogs, the number of canine rabies cases decreases; and when rabies in dogs is eliminated, the threat to humans is also eliminated.

In 1983, Latin America committed to mass dog vaccination: dog rabies cases in the region declined from a peak of 25,000 in 1977 to just 196 in 2011, and human cases fell by 96 per cent to only 15 across the whole continent. The aim of the Global Alliance for Rabies Control is to achieve the same levels of success in Africa and Asia.

Perhaps in a hundred years, rabies will be history. This should be our hope and plan.

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