What Causes Leprosy?

Leprosy is a disease caused by a bacillus, Mycobacterium leprae. It multiplies very slowly and the incubation period can be a number of years (on average about 5 years).

What are the symptoms?

For many people the first signs of leprosy are pale patches of skin or numbness in the fingers or toes. This is because the disease mainly affects the nerves and skin. If left untreated, it can lead to nerve damage, loss of feeling (sensation) and paralysis of muscles in the hands, feet and face.

Can it be cured?

The good news is that most of these consequences can be avoided. Since 1981 leprosy has been treated effectively with multi drug therapy (MDT), a combination of three antibiotic drugs: dapsone, rifampicin and clofazimine. A six to twelve month course of treatment kills the bacteria and cures the person. If treated in the early stages of disease, MDT can usually prevent the onset of impairments and disabilities.

How can it cause disabilities?

The bacteria attack nerve endings and destroy the body’s ability to feel pain and injury. Other nerves controlling muscles can also be damaged, leading to weakness and paralysis, especially of hands and feet. Although the bacteria can damage the nerves directly, the body’s immune response can also cause similar damage through a mechanism we call a leprosy reaction. Without feeling pain, people don’t realise when they injure themselves and their injuries can become infected. Changes to the skin also leave the person susceptible to ulcers, which if left untreated, can cause further damage, wounds and visible disfigurements to the face and limbs. If the facial nerve is affected, this can interfere with a person’s ability to blink, which can eventually cause blindness.

How is it spread? Is it contagious?

Leprosy is most likely transmitted by air through droplets from the nose and mouth, during close and frequent contacts with people who have not yet been treated. While it is spread in a similar way to the common cold, it is much less infectious. It multiplies slowly and the vast majority of people have adequate natural immunity, so don’t contract the disease if exposed. Even when diagnosed, many cases are not considered infectious, and once treatment begins, those infectious cases become non-infectious within the first week of treatment.

But I thought it was eliminated?

The World Health Organization declared leprosy ‘eliminated’ as a public health problem at a global level in 2000. This was based on a definition of less than one case per 10,000 people across a larger population. This did not mean total eradication of the disease: there were still many cases in pockets all over the world, and around 200,000 new cases are reported globally each year. Regrettably, once WHO announced ‘elimination’, resources were often focused on other diseases and efforts to find and treat new cases diminished.

How many people are affected today?

Beyond the 200,000 new cases that are reported annually, there are likely to be many more living with undiagnosed leprosy. Further, there are an estimated 3-4 million people who have been cured of the disease, but experience residual effects of disability, and perhaps as many again who, even without visible impairments, are experiencing the stigma and discrimination that so often accompany the label ‘leprosy’.

Where is it found?

Leprosy is reported in 116 countries (2019 data), with 80% of all new cases occurring in India, Brazil and Indonesia.

How can it be ended once and for all?

It is unlikely that leprosy can be eradicated, as the bacillus also occurs in some animal species (notably the nine-banded armadillo). Among humans, the slow growth of the bacillus means that, even with the best of today’s tools, elimination of the disease is a long journey. ILEP is working in support of WHO’s target of a 70% reduction in new cases by 2030, using the best tools currently available. However, the stigma still associated with leprosy is a barrier to ending transmission, as people are often reluctant to get diagnosed or seek help. It can also have a devastating impact on people’s lives, long after they have been cured. For this reason, ILEP’s strategy is Triple-Zero: we work to stop the transmission of leprosy, prevent disabilities and promote social inclusion by ending stigma and discrimination.