Leprosy Today


Child with leprosy

Today, the diagnosis and treatment of leprosy is easy and most endemic countries are striving to fully integrate leprosy services into existing general health services.
This is especially important for those under-served and marginalised communities most at risk from leprosy, often the poorest of the poor.

Access to information, diagnosis and treatment with multidrug therapy (MDT) remain key elements in the strategy to eliminate the disease as a public health problem, defined as reaching a prevalence of less than 1 leprosy case per 10,000 population. MDT treatment has been made available by WHO free of charge to all patients worldwide since 1995, and provides a simple yet highly effective cure for all types of leprosy.

According to official reports received from 115 countries and territories, the global registered prevalence of leprosy at the beginning of 2006 stood at 219,826 cases, while the number of new cases detected during 2005 was 296,499 (excluding the small number of cases in Europe). The number of new cases detected globally has fallen by more than 111,000 cases (a 27% decrease) during 2005 compared with 2004. During the past four years, the global number of new cases detected has continued to decrease dramatically, by about 20% per year.

Most previously highly endemic countries have now reached elimination, and those few that remain are very close to eliminating the disease. However, pockets of high endemicity still remain in some areas of Angola, Brazil, Central African Republic, Democratic Republic of Congo, India, Madagascar, Mozambique, Nepal, and the United Republic of Tanzania. These countries remain highly committed to eliminating the disease, and continue to intensify their leprosy control activities.

Information campaigns about leprosy in high risk areas are crucial so that patients and their families, who were historically ostracized from their communities, are encouraged to come forward and receive treatment. The most effective way of preventing disabilities in leprosy, as well as preventing further transmission of the disease, lies in early diagnosis and treatment with MDT

Leprosy: the disease

Leprosy is a chronic infectious disease caused by Mycobacterium leprae, an acid-fast, rod-shaped bacillus. The disease mainly affects the skin, the peripheral nerves, mucosa of the upper respiratory tract and also the eyes, apart from some other structures. Leprosy has afflicted humanity since time immemorial. It once affected every continent and it has left behind a terrifying image in history and human memory - of mutilation, rejection and exclusion from society.

Leprosy has struck fear into human beings for thousands of years, and was well recognized in the oldest civilizations of China, Egypt and India. A cumulative total of the number of individuals who, over the millennia, have suffered its chronic course of incurable disfigurement and physical disabilities can never be calculated.

Since ancient times, leprosy has been regarded by the community as a contagious, mutilating and incurable disease. There are many countries in Asia, Africa and Latin America with a significant number of leprosy cases. It is estimated that there are between one and two million people visibly and irreversibly disabled due to past and present leprosy who require to be cared for by the community in which they live.

When M.leprae was discovered by G.A. Hansen in 1873, it was the first bacterium to be identified as causing disease in man. However, treatment for leprosy only appeared in the late 1940s with the introduction of dapsone, and its derivatives. Leprosy bacilli resistant to dapsone gradually appeared

Diagnosis of leprosy

Diagnosis of leprosy is most commonly based on the clinical signs and symptoms. These are easy to observe and elicit by any health worker after a short period of training. In practice, most often persons with such complaints report on their own to the health centre. Only in rare instances is there a need to use laboratory and other investigations to confirm a diagnosis of leprosy.

In an endemic country or area, an individual should be regarded as having leprosy if he or she shows ONE of the following cardinal signs:

  • skin lesion consistent with leprosy and with definite sensory loss, with or without thickened nerves
  • positive skin smears

The skin lesion can be single or multiple, usually less pigmented than the surrounding normal skin. Sometimes the lesion is reddish or copper-coloured. A variety of skin lesions may be seen but macules (flat), papules (raised), or nodules are common. Sensory loss is a typical feature of leprosy. The skin lesion may show loss of sensation to pin pick and/or light touch. Thickened nerves, mainly peripheral nerve trunks constitute another feature of leprosy. A thickened nerve is often accompanied by other signs as a result of damage to the nerve. These may be loss of sensation in the skin and weakness of muscles supplied by the affected nerve. In the absence of these signs, nerve thickening by itself, without sensory loss and/or muscle weakness is often not a reliable sign of leprosy. Positive skin smears: In a small proportion of cases, rod-shaped, red-stained leprosy bacilli, which are diagnostic of the disease, may be seen in the smears taken from the affected skin when examined under a microscope after appropriate staining.

A person presenting with skin lesions or with symptoms suggestive of nerve damage, in whom the cardinal signs are absent or doubtful should be called a `suspect case' in the absence of any immediately obvious alternate diagnosis . Such individuals should be told the basic facts of leprosy and advised to return to the centre if signs persist for more than six months or if at any time worsening is noticed. Suspect cases may be also sent to referral clinics with more facilities for diagnosis.

Transmission of leprosy

Leprosy is known to occur at all ages ranging from early infancy to very old age. The youngest age reported for occurrence of leprosy is three weeks in Martinique (Montestruc & Berdonneau, 1954). The youngest case seen by the author was in an infant of two-and-a-half months, where the diagnosis of leprosy was confirmed by histopathology. Occurrence of leprosy, presumably for the first time, is not uncommon even after the age of seventy.

Method of transmission of leprosy

The exact mechanism of transmission of leprosy is not known. At least until recently, the most widely held belief was that the disease was transmitted by contact between cases of leprosy and healthy persons. More recently the possibility of transmission by the respiratory route is gaining ground. There are also other possibilities such as transmission through insects which cannot be completely ruled out.

Sex distribution

Although leprosy affects both sexes, in most parts of the world males are affected more frequently than females often in the ratio of 2:1. This preponderance of males is observed in as diverse geographic situations as India, the Philippines, Hawaii, Venezuela and Cameroon. Doull et al (1942) from their studies in the Philippines have also pointed out that the difference as a true difference due to higher incidence among males, and not due to differing duration of disease for the two sexes. It it were the latter case, the sex-specific prevalence could be different even with the same sex-specific incidence. It should be pointed out that the male preponderance in leprosy is not universal and there are several areas, particularly in Africa, where there is either equal occurrence of leprosy in the two sexes, or occasionally even a higher prevalence among females. Such situations have been observed in Uganda, Nigeria, Malawi, Gambia, Burkina Faso, Zambia, Thailand and Japan.

The prevalence pool

The prevalence pool of leprosy in a population in general is in a constant flux resulting from inflow and outflow. The inflow is contributed by the occurrence of new cases, relapse of cured cases, and immigration of cases. The outflow is mainly through cure or inactivation of cases, death of cases, and emigration of cases. Of the various factors that influence the prevalence pool, the importance of inactivation of disease and mortality are less well recognized.

Inactivation of disease

Where leprosy treatment facilities exist, inactivation or cure due to specific treatment is an important mode of elimination of cases from the prevalence pool. Even in the absence of specific treatment, a majority of patients, particularly of the tuberculoid and indeterminate types, tend to get cured spontaneously. An earlier study in India had shown that over a period of 20 years, the extent of spontaneous regression among children with tuberculoid leprosy was about 90%. A study in CulionIsland in the Philippines showed that among children self-healing occurred in 77.7% of cases (Lara & Nolasco, 1956). A later study in South India involving long-term follow-up of a high endemic population showed that among newly detected tuberculoid cases of all ages and both sexes, the rate of inactivation was 10.9% per year, the bulk of inactivation in the study being spontaneous (Noordeen, 1975).

Reservoir of infection

The human being is the only known reservoir of infection in leprosy except for the fact that naturally occurring disease with organisms indistinguishable from M.leprae has also been detected among wild armadillos in parts of the southern United States (Walsh et al, 1981). Up to 5% of armadillos in Louisiana have been found to have clinical disease with about 20% having serological evidence of M.leprae infection (Truman et al, 1986). The epidemiological significance of the armadillo is generlly considered to be negligible in spite of occasional cases reported among individuals giving history of handling armadillos (Lumpkin et al, 1983). Among human beings it is the lepromatous cases that carry the largest load of organisms, the maximum load reaching over seven billion organisms per gram of tissue. Patients with non-lepromatous cases carry a very much smaller bacillary load, probably not exceeding one million organisms in total. In additon to clinically identified cases, the occurrence of acid-fast bacilli (AFB) in the skin (Figueredo & Desai, 1949; Chatterjee, 1976) and nasal mucosa of healthy subjects (Chacko et al, 1979) have also been reported. The evidence that the AFB found on such 'carriers' is M.leprae is not conclusive, although there is some evidence that persons who carry such AFB have a higher chance of developing the disease as found during their follow-up (Chatterjee, 1976).

Portal of exit of M.leprae

The two portals of exit of M.leprae often described are the skin and the nasal mucosa. However, the relative importance of these two portals is not clear. It is true that the lepromatous cases show large numbers of organisms deep down in the dermis. However, whether they reach the skin surface in sufficient numbers is doubtful. Although there are reports of AFB being found in the desquamating epithelium of the skin, Weddell et al (1963a) have reported that they could not find any AFB in the epidermis even after examining a very large number of specimens from patients and contacts. Regarding the nasal mucosa, its importance has been recognized as early as 1898 by Schaeffer (1898), particularly tht of the ulcerated mucosa. The quantity of bacilli from nasal mucosal lesions in lepromatous leprosy has been demonstrated by Shepard (1960) as large, with counts ranging from 10 000 to 10 000 000. Pedley (1973) has reported that the majority of lepromatous patients showed leprosy bacilli in their nasal secretions as collected through nose blows. Davey & Rees (1974) have indicated that nasal secretions from lepromatous patients can yield as much as 1 million viable organisms per day.

Viability of M.leprae outside the human host

The possiblity of discharge of M.leprae from the nasal mucosa raises the question of survival of the discharged organisms outside the human host. Davey & Rees (1974) have reported that M.leprae from the nasal secretions can survive up to 36 hours or more. Desikan (1977) has reported on the survival of M.leprae in nasal secretions under tropical conditions for up to nine days. Such survival of the organisms suggests the possibility of contaminated clothing and other fomites acting as sources of infection.

Portal of entry of M.leprae

The portal of entry of M.leprae into the human body is not definitely known. However, the two portals of entry seriously considered are the skin and the upper respiratory tract. With regard to the respiratory route of entry of M.leprae, the evidence in its favour is on the increase in spite of the long-held belief that the skin was the exclusive portal of entry. Rees & McDougall (1977) have succeeded in the experimental transmission of leprosy through aerosols containing M.leprae in immune-suppressed mice, suggesting a similar possibility in humans. Successful results have also been reported on experiments with nude mice when M.leprae were introduced into the nasal cavity through topical application (Chehl et al, 1985). In summary, although no firm conclusions can be reached with regard to the portal of entry, entry through the respiratory route appears most probable, although other routes, particularly broken skin, cannot be ruled out.

Leprosy

Cause

  • Leprosy is a chronic disease caused by a bacillus, Mycobacterium leprae;
  • M. leprae multiplies very slowly and the incubation period of the disease is about five years. Symptoms can take as long as 20 years to appear;
  • Leprosy is not highly infectious. It is transmitted via droplets, from the nose and mouth, during close and frequent contacts with untreated cases.

Symptoms

  • Leprosy mainly affects the skin and nerves;
  • If untreated, there can be progressive and permanent damage to the skin, nerves, limbs and eyes.

History

  • Leprosy was recognized in the ancient civilizations of China, Egypt and India;
  • The first known written mention of leprosy is dated 600 BC;
  • Throughout history, the afflicted have often been ostracized by their communities and families.

Treatment today

  • Leprosy is a curable disease and treatment provided in the early stages averts disability;
  • With minimal training, leprosy can be easily diagnosed on clinical signs alone;
  • A World Health Organization (WHO) Study Group recommended multidrug therapy (MDT) in 1981. MDT consists of three drugs: dapsone, rifampicin and clofazimine. This drug combination kills the pathogen and cures the patient;
  • MDT is safe, effective and easily administered under field conditions. MDT is available in convenient monthly calendar blister packs to all patients;
  • Since 1995, WHO provides free MDT for all patients in the world, initially through the drug fund provided by the Nippon Foundation and since 2000, through the MDT donation provided by Novartis and the Novartis Foundation for Sustainable Development.

High effectiveness of multidrug therapy

  • PB patients treated with MDT are cured within six months;
  • MB patients treated with MDT are cured within 12 months;
  • Patients are no longer infectious to others after the first dose of MDT. In other words, transmission of leprosy is interrupted;
  • There are virtually no relapses, i.e. recurrences of the disease after treatment is completed;
  • No resistance of the bacillus to MDT has been detected;
  • WHO estimates that early detection and treatment with MDT has prevented about four million people from being disabled. This suggests great cost-effectiveness of MDT as a health intervention, considering the economic and social loss averted.

History of treatment

  • The first breakthrough occurred in the 1940s with the development of the drug dapsone, which arrested the disease. But the duration of the treatment of leprosy was many years, even a lifetime, making it difficult for patients to follow;
  • In the 1960s, M. leprae started to develop resistance to dapsone, the world’s only known anti-leprosy drug at that time;
  • Rifampicin and clofazimine, the other two components of MDT, were discovered in the early 1960s.

The elimination of leprosy as a public health problem

  • In 1991 World Health Assembly passed a resolution to eliminate leprosy as a public health problem by the year 2000. Elimination of leprosy as a public health problem is defined as a prevalence rate of less than one case per 10 000 persons; The target was achieved on time.
  • The widespread use of MDT has reduced the disease burden dramatically;
  • Over the past 20 years, more than 14 million leprosy patients have been cured about 4 million since 2000.
  • The prevalence rate of the disease has dropped by 90% – from 21.1 per 10 000 inhabitants to less than 1 per 10,000 inhabitants in 2000.
  • A dramatic decrease in the global disease burden: from 5.2 million in 1985 to 805 000 in 1995 to 753 000 at the end of 1999 to 286 000 cases at the end of 2004.
  • Leprosy has been eliminated from 113 countries out of 122 countries where leprosy was considered as a public health problem in 1985. An additional 13 countries achieved the elimination target since 2000.
  • A 20% annual decrease in new cases detected globally since 2001.
  • Absence of resistance to drugs used in MDT.
  • Efforts currently focus on eliminating leprosy at a national level in the remaining endemic countries and at a sub-national level from the others.

Figures on the current leprosy situation

  • Approximately 410 000 new cases of leprosy were detected during 2004 compared to a peak of 804 000 in 1998. At the beginning of 2005, 290 000 cases were undergoing treatment;
  • In 9 countries in Africa, Asia and Latin America leprosy is still considered a public health problem; These countries account for about 75% of the global disease burden.
  • According to the latest available information, intensive efforts are still needed to reach the leprosy elimination target in five countries: Brazil, India, Madagascar, Mozambique, and Nepal.