Leprosy — down but not out
When Azir Ahmad, a young farmer from a remote village in South India, developed leprosy in 1964, doctors told him he would need to take the drug dapsone for many years — probably for the rest of his life.
Free medication was available from the government, but Ahmad had to collect it every month from Bangalore, his nearest city. Having neither time nor money to make the monthly journey, Ahmad's disease progressed, leaving him scarred, disfigured, and abandoned by his family.
India announced this month that, by World Health Organization (WHO) standards, leprosy is still a public health problem. Yet after the WHO's 2000 declaration that the disease was no longer an issue for public health, awareness and treatment campaigns have lost momentum and fewer researchers now undertake work on leprosy.
Experts are warning that this means that new cases could be going undetected, and that focusing only on the numbers of new cases hides the bigger problem of disability resulting from the disease.
During the 1960s, resistance to dapsone began to emerge in Mycobacterium leprae, the bacterium that causes leprosy, ruling out the only treatment option for those who did manage to get access to it. The 1980s saw the discovery of multi-drug treatment for leprosy: a combination of dapsone, rifampicin and clofazimine, given over six months to a year. It cures leprosy and can prevent disability if the disease is caught in its early stages.
Combination treatment made elimination a real possibility, and in 1991 the WHO announced it would help eliminate leprosy by 2000. As part of a global campaign, multi-drug treatment was provided free to people with leprosy worldwide.
Kalasha Govinda, a specialist in leprosy and former joint director of India's National Leprosy Eradication Programme for Karnataka State, recalls that the WHO resolution had a tremendous impact on his region, when doctors travelled from door to door through the worst affected areas, conducting mass screening to identify and treat patients.
The goal of the WHO's campaign was to reduce leprosy prevalence — that is, the number of registered cases at a particular time. The WHO definition of 'elimination' is a prevalence of less than one case per 10,000 people. In 1985, leprosy was a major problem in 122 countries. In India, one of the worst affected countries, prevalence was more than forty times the WHO's target figure.
During the first decade after multi-drug treatment was introduced, prevalence fell dramatically as a huge 'backlog' of cases was cleared, falling from around 12 million cases in 1985 to less than one million by 1996. By 2000, the WHO declared that leprosy had been 'eliminated as a public health problem at a global level'.
But these figures mask a more complex situation. In 2004, ten countries were yet to reach WHO's elimination target (see map). Six of these (India, Brazil, Madagascar, Mozambique, Nepal and Tanzania) have 90 per cent of the world's leprosy cases, with three quarters of them in India alone.
According to the WHO's technical advisory group, the ten countries yet to meet the target as of February 2004 are Angola, Brazil, Central African Republic, Democratic Republic of Congo, India, Liberia, Madagascar, Mozambique, Nepal and Tanzania.
Last month the International Leprosy Union and the WHO announced they had reached the "last mile in the battle against leprosy" in India, aiming to eliminate it from the country by the end of 2005. As of 31 March 2005 the prevalence in India was 1.34 cases per 10,000 – still higher than the WHO's target figure.
But Diana Lockwood, an infectious disease specialist and leprologist at the London School of Hygiene and Tropical Medicine, believes that focusing on the number of registered cases can be misleading. Since patients are only registered while they are on medication, figures vary depending on how long treatment lasts. The WHO's target could simply be reached by shortening treatment regimes and failing to diagnose cases, Lockwood fears. In the long term, a backlog of cases could build up and the problem may reappear.
These concerns seem to be borne out by the number of new cases that appear every year. Even in 2000, when the WHO declared leprosy eliminated, there were 719,330 new cases worldwide. The fact that all over the world people (including children) are still developing leprosy indicates that the disease is still being transmitted, says Lockwood.
She adds "although the number of new cases detected each year has been falling since 2002, it would be hasty to read too much into this".
There are huge uncertainties — for example the number of 'fake' or double-counted cases could be as high as 20 per cent. And on the other hand, there are probably many genuine cases going undetected — particularly since campaigns to actively detect leprosy patients are being scaled down.
Some health workers fear that doctors are being discouraged from detecting cases in the rush to meet the target.
Concentrating on reducing the numbers of registered cases, says Lockwood, diverts attention from the most important issue: preventing disability. Between two and three million people worldwide are disabled as a result of the disease.
Among them is Krishnaswamy from Madras, who was cured of leprosy more than five years ago, after multi-drug treatment, so he is no longer registered as a leprosy patient. But he was left with insensitive hands and feet, and was at risk of further injury. After a minor fall he developed ulcers on his feet that failed to heal, leaving him unable to walk.
"Teaching patients to take care of their injuries is one of the most important tasks," says Lockwood.
The key to preventing deformity is to detect leprosy in its early stages, says Govinda. There is no doubt that the situation has improved following two decades of outreach programmes, he adds. In 1986, almost one in five of all newly diagnosed leprosy cases he saw already had some kind of deformity. Now, that figure is closer to one in 100.
However, constant vigilance is needed. WHO guidelines now advise countries to integrate leprosy treatment into their existing national health services, rather than tackling it with specialised teams. Busy local doctors may fail to spot the early signs of the disease.
A survey by the Chengalpattu-based Central Leprosy Teaching and Research Institute of 149 men and women diagnosed with leprosy during a campaign in Tamil Nadu in 1999 showed that 30 per cent of them had visited their doctor for other reasons but the disease had not been picked up.
Health workers are becoming complacent, one campaigner told SciDev.Net: "Once the WHO declared leprosy eliminated at a global level, it became less of a priority in people's minds."
Can leprosy be eradicated in the 21st century?
Elimination — reducing the disease to an extremely low level — can often be confused with eradication, which is wiping out a disease completely. Leprosy elimination will not necessarily lead to eradication unless transmission can be stopped. Patrick Brennan, a researcher at Colorado State University, believes that multi-drug treatment alone will not be enough to eradicate leprosy.
Leprosy is thought to be transmitted through nasal secretions. It is difficult to diagnose in its early stages and there are no simple diagnostic tests. The main signs are insensitive or discoloured skin patches, easily confused with other injuries or even birthmarks. Until patients are diagnosed and start taking treatment, they can spread the infection to others. Since people can be infected for up to 20 years before developing symptoms, transmission is hard to control.
We need new ways of diagnosing leprosy in its early stages, and a better understanding of transmission, says Brennan. With an ever-shrinking community of leprosy researchers, as money and staff are diverted towards HIV and tuberculosis, progress will not be an easy task.
However, the sequencing of the leprosy genome in 2000 revived waning interest in leprosy research and has yielded some exciting results. Brennan says it is now possible to detect and track individual strains of Mycobacterium leprae through communities. In a few years, we will have a much better understanding of how the disease is transmitted, allowing us to develop new countermeasures, he says.
New diagnostic tests are also a real possibility. Specific antigens (proteins that can trigger an immune response) have been identified that are uniquely associated with the leprosy genome and could be used to detect infection before symptoms appear.
Research on its own will not be enough. Poverty eradication is equally important. Leprosy is more common, and its effects more devastating, where there is overcrowding, poor nutrition, and lack of education.
There is no doubt that the past 20 years have seen remarkable progress in the fight against leprosy. But the battle is not yet won and premature euphoria could backfire. "There is no room for complacency or a decrease in control efforts" warns Lockwood. The "last mile" may be the biggest challenge of all.