Throughout the centuries, leprosy has been characterized as a disease responsible for serious deformities resulting in stigmatization and psychological and social suffering. Probably one of the first examples of Public Health regarding leprosy can be found on the Leviticus, where priests are taught the first notions of leprosy diagnosis which were the segregation of those suffering such terrible disease (at that time seen as prescribed environmental infection control strategies). There is also a mention of leprosy in Al-Bukhari’s Muslim Hadith of Prophet Mohammed’s dread of leprosy (“Escape from the leprous the way you escape from a lion”). Since then leprosy is a metaphor for stigma. Even not so long ago, during the boom years of HIV, those afflicted by AIDS were stigmatized as “unclean”, “outcast” or “incurable” and, hence, pejoratively called as the new lepers of our era.
Leprosy is caused by Mycobacterium leprae and Mycobacterium lepromatosis, the former being one of the first, if not the first, micro-organism directly associated with a specific human disease. M. leprae was first discovered by the Norwegian physicist Gerhard Hansen (1841-1912), hence leprosy is also known as Hansen’s Disease.
However, there are still big gaps in the understanding of leprosy, not only at pathological and immunological levels, but also at some points of its epidemiology. So far, and very roughly, we know that infection does not necessarily lead to any symptoms or lesions specific for the disease. Moreover, we assume that M. leprae is not very pathogenic and that most infections do not result in symptoms. Early symptoms can be self-limiting and skin lesions can heal spontaneously.
How is leprosy distributed?
The total number of leprosy patients in the world varies from 10 to 12 million, increasing by about 500k declared cases every year. The last estimate done by the World Health Organization (WHO) distributes the disease in this way:
– Asia: 62%
– Africa: 34%
– South America: 3%
– Rest of the World: 1%
Leprosy is known to happen at all ages, ranging from early infancy (the youngest case reported was a three-week old baby in Martinique) to old age. Also, although leprosy affects both sexes in most of the World, males a affected more frequently than females, at a ratio of approximately 2:1.
The factors that contribute to this uneven distribution are, generally, climatic conditions, diet, nutrition and socio-economic factors (literacy, caste, etc.)
How is leprosy transmitted?
The exact mechanism of transmission is still unknown to us, but it is widely accepted that the main way of transmission is through the respiratory route, although there are other possibilities such as transmission through insects that cannot be ruled out.
Nowadays it is thought that there are two main portals of entry for M. leprae: the skin and the upper respiratory tract. Which is the main one? It is still unclear, although the entry through the respiratory tract is the most favoured one (this goes against the historically long-held view that the main portal of entry for M. leprae was the skin).
When M. leprae invades the human body, there are two actions that can take place: tuberculoid leprosy (TT) and lepromatous leprosy (LL).
In tuberculoid leprosy, which is the milder form of the disease, the body’s immune cells attempt to seal off the infection from the rest of the body by surrounding the offending pathogen. Because this response occurs in the deeper layers of the skin, the hair follicles, sweat glands and nerves can be destroyed, resulting in the skin being discoloured, dry and lacking of sensitivity. When nerves of the face, arm and legs are involved, they become enlarged and can be easily felt by the doctor. Also, the reduced numbers of bacteria in this type of leprosy leads to it being referred as paucibacillary leprosy (PB) and is the most prevalent one.
In lepromatous leprosy, which is the most contagious form of the disease, the body’s immune system is unable to organize a strong response to the invading organism. Because of this, M. leprae multiplies freely in the skin. This type of leprosy is also known as multibacillary leprosy (MB), because of the presence of large numbers of bacteria. The main feature of this disease is the appearance of large nodules or lesions all over the body, face and mucous membranes. This type of leprosy can lead to blindness, drastic change in voice and mutilation of the nose.
What are the symptoms?
In tuberculoid leprosy, a rash appears, consisting of one or a few flat whitish areas, which will be numb due to the bacteria damaging the underlying nerves.
In lepromatous leprosy, many small bumps or larger raised rashes of variable size and shape will appear on the skin, therefore the numbed areas of the body will be larger than in TT.
The most severe symptoms result from infection of the peripheral nerves, causing the deterioration of a person’s sensitivity to pain and temperature. Repeated damage could eventually lead to loss of fingers and toes, as well as muscle weakness. Skin infection could lead to areas of swelling and lumps, which might result on disfiguring the face.
During the course of untreated or even treated leprosy, the body’s immune response may produce inflammatory reactions, which in turn can produce fever and inflammation of the skin, peripheral nerves, lymph nodes, testes, kidneys, liver and eyes.
And with this I end the first entry on leprosy. On the next few days I will write about the management of leprosy (diagnosis, treatment, etc.) and two more posts to briefly write about leprosy through History and a homage post to one of the most prominent scientists on the leprosy field.
I hope that you enjoyed the reading and that you have a nice day. God bless you.