Keeping rabies on a tight leash

The very word “rabies” arouses dread. Those unfortunate enough to contract the disease, typically after being bitten by an infected dog, are almost certain to die.

After the rabies virus makes its way from the site of the bite, via the nerve fibres, to the spinal cord and brain, symptoms of the disease appear. The common image of a rabies sufferer is of one who is afraid of water (known as hydrophobia).

That form of the disease, known as “furious rabies,” is easily diagnosed, according to S.N. Madhusudana, Head of the Department of Neurovirology at the National Institute of Mental Health and Neuro Sciences in Bangalore. Such individuals can be highly excited and agitated, psychotic and often unable to tolerate any breeze or bright light.

Paralytic form

But others can suffer from a less dramatic form of the disease, which too is fatal and characterised by a growing paralysis of the muscles. “The paralytic form of rabies is often misdiagnosed, contributing to the under-reporting of the disease,” according to the World Health Organisation (WHO).

The handful of individuals who are known to have survived after developing rabies all had the paralytic type, remarked Dr. Madhusudana. None have survived “furious rabies.”

WHO estimates that more than 55,000 people die of rabies every year, with more than 95 per cent of those deaths occurring in Asia and Africa.

India accounts for a large proportion of the world’s rabies cases. A detailed WHO-sponsored assessment carried out in 2003 by the Association for Prevention and Control of Rabies in India (APCRI) estimated that there were more than 17,000 “furious rabies” cases in the country annually. With an addition of 20 per cent to take into account paralytic or atypical forms of the disease as well, the total number of rabies deaths each year was put at about 20,000.

The study found that well over 80 per cent of rabies deaths occurred among the poor and low-income groups. Rural areas were disproportionately affected, having three times as many cases as urban parts of the country. Some 70 per cent of the victims were male. About a third of deaths were in children below the age of 14 years.

Once the famed French scientist, Louis Pasteur, demonstrated the first vaccine that was effective against rabies in 1885, it was possible to lift what for millennia had been a death sentence. Much safer vaccines were subsequently developed. However, it was only in 2004 that India stopped using a vaccine made using sheep brain, which could produce neurological complications in some people, and moved to ones made with cell culture and duck embryo.

A course of such vaccines given to a person as soon as possible after being bitten by a dog (or another animal) can prevent rabies. Injecting the vaccine into the skin (known as intradermal vaccination), instead of into the muscle, allowed a lower dose to be used, thus lowering the cost of vaccination, observed M.K. Sudarshan, president of the Rabies in Asia Foundation and dean and principal of the Kempegowda Institute of Medical Sciences in Bangalore.

In severe cases with bleeding wounds, ready-made antibodies, known as immunoglobulin, may also need to be given to provide immediate protection while the vaccine takes effect.

Treatment and the States

About 20 States now provide intradermal vaccination either free or at a subsidised cost through government or municipal corporation hospitals, Dr. Sudarshan told this correspondent. Some 10 to 15 States were also similarly providing rabies immunoglobulin treatment.

The availability of such treatment appears to have had an impact, especially in cities. According to Dr. Sudarshan, who led the 2003 study, hospital statistics from Delhi, Kolkata, Hyderabad and Bangalore indicated that while the number of people they were treating for animal bites had remained largely stable, human rabies cases had come down in recent years.

The 2003 survey showed that dog bites were responsible for about 96 per cent of the rabies cases in the country. “The most cost-effective strategy for preventing rabies in people is by eliminating rabies in dogs through vaccination,” according to WHO. Control of canine rabies could be achieved by sustained vaccination that covered 70 per cent of the dog population.

Ministry’s initiative

In countries that make up North, Central and South America, mass vaccination of dogs and treatment of people who might have been exposed to the virus led to an 80 per cent decline in the number of human and canine rabies cases over a 10-year period. In India, given the problem posed by large numbers of street dogs, it is necessary not just to vaccinate them against rabies but also to limit their breeding potential by sterilising them.

“Help In Suffering,” a Jaipur-based animal welfare organisation, has been carrying out such birth control and vaccination activities since late 1994. About 3,000 street dogs were being sterilised and vaccinated each year, said Jack F. Reece, a British veterinary surgeon who has been working with the organisation for over a decade. Besides, a further 3,000 to 4,000 dogs were vaccinated against rabies.

Although Jaipur had grown substantially, there was evidence that the number of dog bite victims seen in the main hospital in the city had declined over the duration of the animal birth control programme, he added.

The Animal Welfare Board of India already had memoranda of understanding with over 30 civic bodies for undertaking birth control and vaccination of dogs, according to its chairman, Major General (retd.) Dr. R.M. Kharb. Some 65 non-governmental organisations were involved in these activities. The programme had performed well in Jaipur, Kalimpong in West Bengal and Chennai where there have not been any rabies cases for the last three years.

As part of an initiative by the Union Government’s Ministry of Health & Family Welfare to curb rabies, existing dog birth control and vaccination efforts would be further intensified and also extended to more towns and cities, he added.

Reducing the country’s burden of rabies required a consistent and well thought-out strategy to take proven interventions, targeted at humans as well as the dog population, down to villages where most cases occurred, remarked Manish Kakkar, a public health specialist in infectious diseases at the Delhi-based Public Health Foundation of India. Only Tamil Nadu had a system in place to maintain a steady supply of vaccines right up to the local public health centres for treatment of people.

In much of India, measures to protect humans and control the threat posed by dogs had often been patchy and concentrated in urban areas, he pointed out.

gopal.raj@thehindu.co.in