It is 125 years since the famous French scientist Louis Pasteur first demonstrated an effective vaccine against rabies. Yet even today, more than 55,000 people suffer agonising deaths each year as a result of this terrible disease. About 95 per cent of those lives are lost in Asia and Africa. India, where on average a person dies of rabies every half an hour, has the highest death toll of any country.
The World Rabies Day, which will be observed on September 28, the death anniversary of Louis Pasteur, is intended to draw attention to the fact that such a loss of life is wholly preventable and much can be done to reduce the risk of people contracting the disease.
The rabies virus circulates in animals, and humans catch the disease when they are bitten or scratched by an infected animal. In Asia and Africa, humans are most likely to get it from a rabid dog.
After the virus gains entry into a human body, it initially replicates in the muscle, says S.N. Madhusudana of the National Institute of Mental Health and Neuro Sciences (NIMHANS), Bangalore, who studies the rabies virus. Subsequently, it goes on to infect nerve cells in the spinal cord and then makes its way to the brain, The first symptoms manifest when the virus begins to proliferate in the brain, which normally happens one to three months after the person gets infected. Death then usually ensues in a matter of days.
Only a small number of people have recovered after developing rabies and there is still no proven cure. However, vaccines have been remarkably effective in preventing the disease even when given after a person has been exposed to the virus.
Louis Pasteur and his colleagues produced the first such vaccine by infecting rabbits with rabies. Their spinal cords were then removed and dried for varying lengths of time in order to produce weakened forms of the virus. The vaccination consisted of a series of injections, with the most weakened virus being given first and progressing to stronger forms.
The vaccine was successfully tested in dogs. Then in 1885, nine-year-old Joseph Meister, who turned up at Pasteur's laboratory after being severely bitten by a rabid dog, became the first person to receive the vaccine. A year later, hundreds more had been successfully inoculated. This vaccine continued to be produced well into the 1960s, according to Noël Tordo of the Institut Pasteur in France.
The Semple and newer vaccines
In 1911, Lt. Col. Sir David Semple, who headed the Central Research Institute at Kasauli in Himachal Pradesh, came up with a simpler way to make a vaccine by replicating the rabies virus in the brain of sheep. This vaccine was extensively used in India.
Although the Semple vaccine produced severe neurological complications and paralysis in some people, its use in India was finally discontinued only in 2004. Now, purified cell culture and duck embryo vaccines are used instead.
But these newer vaccines are more expensive. A course of five injections needed for post-exposure treatment can cost Rs. 1,500. Access to such treatment is also an important issue in India. A 2003 survey found that over 80 per cent of rabies deaths in the country occurred among the poor and those with low incomes. Villagers accounted for three-quarters of the fatalities.
One way to greatly reduce the cost of treatment is to give the vaccine into the skin rather than into the muscle as is usually done. Such intra-dermal vaccination, as it is called, evokes just as good an immune response with a smaller dose of the vaccine, observes M.K. Sudarshan, president of the Rabies in Asia Foundation and dean and principal of the Kempegowda Institute of Medical Sciences (KIMS), Bangalore. But health care professionals needed to be trained to administer it correctly.
Some 13 States have already introduced intra-dermal rabies inoculation. However, such treatment was available only in the government sector and that too largely in urban areas, Dr. Sudarshan points out. Uttar Pradesh, Kerala and Orissa have made good progress in making it more widely available.
Besides, those who receive severe wounds from a rabid animal also need to be given ready-made antibodies known as immunoglobulin to protect them while the vaccine takes effect, says Dr. Madhusudana. Such immunoglobulin injections were somewhat expensive and not always readily available. They were therefore often not administered. His hospital sees half a dozen cases of rabies each year where individuals have been partially vaccinated but not given immunoglobulins.
The Kerala Government has taken steps to improve access to anti-rabies treatment. In the last one and half years, the number of anti-rabies clinics offering free intra-dermal vaccination has been increased from five to 60, says Thomas Mathew, the State nodal officer for the programme and professor of Community Medicine at the Thiruvananthapuram Medical College. There would be at least one institution in each district that could provide immunoglobulins.
Dogs, a key factor in India
Dogs are responsible for over 97 per cent of cases in the country. Consequently, measures to control the stray dog population and vaccinate such dogs as well as pet animals against rabies are important.
Post-exposure vaccination of people is expensive, points out Maj. Gen. Dr. R.M. Kharb (retired), chairman of the Animal Welfare Board of India. If half that amount is spent on mass vaccination of dogs and their sterilisation, the dog menace and rabies can be brought under control.
The responsibility for sterilising stray dogs and vaccinating them against rabies lies with civic bodies, he says. In Jaipur and Chennai, where non-governmental organisations ran large-scale programmes for this purpose, there have not been any rabies cases in the last two to three years. Its incidence has also substantially come down in metropolitan Delhi, Kolkata, Hyderabad and Bangalore.
According to the World Health Organisation (WHO), Sri Lanka and Thailand have sharply reduced the number of human rabies deaths with mass dog vaccination campaigns, improved access to post-exposure treatment and an effective vaccine delivery system.
