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by Aryadasa Ratnasinghe

In Sri Lanka, on average, about 900 people are bitten by rabid dogs annually, and out of them about 22 per cent die an agonising death having become infected with the deadly virus. Once symptoms appear, the disease does not last for more than a week. The incubation period, or the time between infection and appearance of symptoms, according to international sanitary regulations, is 11 days to one year (maximum range) and 4 to 9 weeks (usual range).

Rabies, a word derived from the Latin etymon 'rabere' (to rave or become mad), is a viral disease that affects a wide range of mammals (warm-blooded animals), such as dogs, cats, foxes, skunks, vampire bats, horses, cattle, sheep, goat etc., but humans are the most vulnerable to the lethal disease, when mad dogs prowl upon them when confronted unexpectedly. Rabies, in view of its pathogenic symptoms, is also known as 'hydrophobia' (fear of water), because the disease is very hypersensitive to water due to the spasms brought on by drinking or the sight of water.

Rabies, being an acute viral encephalomyelitis, involves the spinal cord and the brain. After entering the human body, the virus keeps multiplying slowly, at the bite site, and later invades the nearest nerve tissue and, gradually, within weeks or months, ascends into the spinal cord and then to the medulla oblongata of the brain, causing the disease, unless prophylactic treatment is given to the victim in time, to prevent death.

It is said that the vaccines available to immunise rabies are Human Diploid Cell Vaccine, Vero Cell Vaccine, Primary Chick Embryo Vaccine and Duck Embryo Vaccine.

The rabies serum is of two kinds. One is Human Rabies Immunoglobulin (human serum therapy), and the other is Equine Rabies Immunoglobulin (horse serum therapy), and these inactivate the virus causing immunity or resistance to infection.

soap and water

Alcohol, detergents, tincture of iodine and other suitable virucidals (virus killers) are recommended as first-aid treatment at home, and the most important being to wash the bite site with soap and water.

Rabies is not a human disease, but one transmitted by animal to man, and hence known as zoonosis. Most of the human pathogens which have emerged during the recent years, have not proved so lethal than rabies. Once a person is bitten by a dog, and not knowing whether the animal is rabid or not, the best course of action is to seek prophylactic treatment available in most hospitals.

Next it is important to watch the condition of the dog for about two weeks, to ascertain whether it is rabid or not. If the animal were to die within the period, its severed head should be taken to the Medical Research Institute (MRI) in Borella for investigation. It was Louis Pasteur (1822-1895), Professor of Chemistry and Microbiologist, who showed in 1881, that sheep and cows vaccinated with the attenuated bacilli of anthrax, received protection against the disease. In 1885, he produced a vaccine for the treatment of rabies, which was a great achievement in the field of preventive medicine. Since then, many lives have been saved from the brink of death having become infected with rabies.

Rabies is severe when the portal of entry of the virus is the head, neck, face, fingers, genitalia, but less severe when a wound is licked by a rabid dog or a superficial bite on the leg, because the portal of entry varies according to the distance from the brain. The symptoms of rabies are fever, general malaise, paraesthesia around the bit site. Episodes of hyperactivity, aggression and convulsions are common. Paralysis is common, sometimes leading to delirium tremens and coma. Death follows inexorably.

two kinds

Rabies are of two kinds. One is known as 'furious rabies' where hypersensitivity predominates and the animal becomes restless and excited. It may attack anyone it comes across while on the move. With drooping ears, frothing mouth, tongue jutting out to a side and tail bent downwards, the dog will run forward in its mad rush. It may even attack its master or others of the household due to reflex action.

The other type is known as 'dumb rabies' where paralysis is the common symptom. The dog becomes inactive and prefers to live in seclusion and away from disturbances. It may prowl upon anyone if it becomes angry, or even if one tries to pet it. These dogs are silent carriers of rabies. Since they find it difficult to open their jaws, they seldom bite. It looks as if a bone had stuck in its throat. A dog's saliva becomes infective up to one week prior to it becoming rabid and remains so up to the time of its death which may not last more than a week. It is said that some dogs survive rabies, but majority of them die of paralysis of the hind legs. It takes about 10 days for a previously unvaccinated person to develop anti-bodies to fight the virus through vaccination. Anti-rabies immunoglobulin must be administered on the first day of treatment to bridge the unprotected period. Once injected at the bite site, the vaccine neutralises the activity of the virus.

According to medical opinion, post-exposure treatment with vaccine and immunoglobulin provides virtually 100 per cent protection against the disease, if administered immediately under medical advice. The problem, however, is that rabies immunoglobulins and modern vaccines are expensive and not within the reach of the common man. Only expert post-exposure treatment, using modern cell culture vaccines, can reduce the human death toll from rabies, as has been demonstrated in Thailand. The dramatic reduction so achieved was brought about by abolishing the use of nerve-tissue-derived vaccines since 1986.

initial step

The Medical Research Institute (MRI) is the only institution in Sri Lanka, where rabies diagnosis is performed on suspected specimens brought for investigation. The innervation of the site of viral entry, proximity of the site to the central nervous system, severity of the bite, quantity of virus innoculated during the bite, age and the immune status of the host are important factors needed for proper investigation. The initial step in rabies control urgently requires sending of the suspected dog's head for examinations to the MRI.

According to the MRI, there are two types of tests done in the laboratory to ascertain the condition of the dog. One is known as Direct Smear Test (DST), and the report is issued within the day, from the time it was handed over for examination. This test is done to find for 'Negri' bodies in the brain cells, the name derived from the person who found them out after much research. If the test proves to be positive, the other test is not done. The other test is known as the Fluorescent Anti-body Test (FAT), which takes two days to perform.

It is said to be more expensive, complicated and very sensitive, unlike the other. It involves testing for the rabies 'antigen' which stimulates the production of anti-bodies in the blood. This test takes about 72 hours. Since the MRI is open to the public, on all days the suspected specimens can be produced at any time on any day of the year. As a precautionary measure, all puppies should be immunised against rabies, at the age of 6 weeks, and a booster given at the age of 3 months, and annually, thereafter, to protect the animal from a possible attack.

The law relating to rabies in Sri Lanka is incorporated in the Rabies Ordinance No. 7 of 1893, and came into effect on January 2, 1895. It is a small statute, having only 16 sections, and dealing with the law enforcement pertaining to the prevention of a possible outbreak of rabies within any local authority. In 1975, the Ministry of Health launched the first five-year Rabies Control Programme, assisted by the WHO.

Rabies control

The Colombo Municipal Council intensified its Rabies Control Programme by compulsory vaccination of dogs against rabies and seizing stray dogs or street dogs that roam about freely in search of food and water. But the selection of dog-seizers posed a problem because there were very few who were willing to undertake the job. Even the unemployed were either hesitant or recalcitrant to seize stray dogs, as it was imbued with the social stigma and the religious taboo over killing.

People called them 'balu abaran' with ostracism. The public did not support them, and wherever possible, the dogs were chased away to safety.

The law insists and requires any person whose dog is rabid, or bitten by a dog suspected of rabies, to inform the nearest police station, and to have the animal securely tied or otherwise confined, to prevent it biting any person when he comes upon the animal unawares. It shall be the duty of the police officer to destroy every dog which is rabid and, in suspected cases, to make frequent visits to check the condition of the dog so suspected. The health authorities insist on public co-operation to eradicate the lethal disease.

Rabies is more prevalent in urban areas than in rural areas, and more dogs are found roaming along the roads where easy access is available to houses. Sri Lanka being a Buddhist country, does not encourage killing of stray dogs, and this has posed a problem to local authorities to eradicate the menace. In most advanced countries, dogs are not seen on the streets, and the domesticated dogs are kept house-bound.

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Copyright 2001 The Associated Newspapers of Ceylon Ltd.
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