Introduction

This chapter introduces leprosy, an infection that is still misunderstood and considered a neglected tropical disease but declining in frequency, according to the World Health Organization. The bacteria that cause leprosy, Mycobacterium leprae and Mycobacterium lepromatosis, are outlined, as well as how a relative strength of a person’s immune system determines how leprosy affects the body. Although leprosy is curable, associated stigma and disability remain common challenges for people with the disease in parts of the world. The goals and structure of the book are outlined, ten myths that still pervade society at large are listed, and the use of the word “leper” discussed. Based on World Health Organization data, the chapter also explores the frequency of leprosy today, where the infection remains a challenge, and the history of detecting and reporting evidence for leprosy in living populations. Finally, the reasons why bioarchaeologists have an interest in this infection are explored.

Past and Present Diagnosis, Treatment, and Prognosis

This chapter considers diagnosis of leprosy both today and in the past. Recently, molecular methods have contributed to diagnosis, detecting drug resistant M. leprae strains and bacterial strain-specific markers, assessing exposure to M. leprae, and tracing transmission patterns. Treatment of leprosy is focused on drug therapy, but a holistic approach is needed from both medical and social perspectives. Since the 1940s drug therapy has contributed to leprosy’s decline, free for over twenty years. However, access can be a challenge. Effective vaccines for preventing leprosy need development. Equally important is the prevention and treatment of damage to the hands and feet due to loss of skin sensation. Historically, diagnosis of leprosy in the past could be done by inexperienced people and often seemed inappropriate. However, rational tests are described, such as looking at urine and blood, and focusing on the skin lesions. Treatments were varied, such as bathing, dressing skin lesions, cautery of body parts, and herbal remedies. The most widespread “treatment” was segregation into leprosy hospitals (leprosaria). It is unclear how many people in the past were segregated in this way, compared to the number more readily accepted within their communities.

A Future for Leprosy: Clinical and Bioarchaeological Perspectives

This concluding chapter considers the overall findings of the book, some limitations of the data, and addresses the myths of leprosy outlined at the start of the book. All the ten myths are dismissed. For example, leprosy can be cured using antibiotic therapy, which has been free for all who need it since 1995; leprosy as we know it today is not described in the Bible—this misconception is related to a mistranslation of a Hebrew word; leprosy is a problem for people today. While figures from the World Health Organization indicate that new “cases” of leprosy have shown a steady decline since the late 1990s, the legacy of leprosy (impairment, stigma, isolation) remains; and all people with leprosy were not necessarily segregated from society in the past—the bioarchaeological data show that not everyone with leprosy was segregated and that people likely remained part of their communities. Finally, a future for leprosy in our world is considered, alongside its future study in history and bioarchaeology through an evolutionary perspective that is ethically grounded, not forgetting that using the word “leper” is not advised.

The Bioarchaeology of Leprosy

This chapter explores the bone changes in the skeleton related to leprosy (paleopathology). Diagnosing leprosy in skeletons ideally requires a complete well-preserved skeleton. The facial, hand, and foot bones are affected, but only a few percent of untreated people will develop bone lesions, and the type of leprosy depends on the resistance of their immune system to M. leprae. Most skeletons diagnosed will display lesions due to the low-resistant form: lepromatous leprosy. Damage to the peripheral nerves by M. leprae is responsible for the alterations to the hand and foot bones. The bone changes of the skull represent the direct effects of M. leprae being inhaled into the mouth and nose. Beyond visual/macroscopic analysis, imaging and microscopy have been used for diagnosis. Biomolecular analysis is the main advance in analytical methods (mainly focusing on ancient DNA). Sequencing of the modern M. leprae and M. lepromatosis genomes have provided data for comparative analyses and testable hypotheses regarding the origin, evolution, and history of leprosy. These data are enabling paleogeneticists, historians, and bioarchaeologists to re-evaluate the long history of leprosy in relation to historical accounts of the drivers for the migration of people with leprosy across the globe.

Reconstructing the Origin, Evolution, and History of Leprosy

This chapter synthesizes the skeletal evidence for leprosy documented in the previous chapter to explore the origin, evolution, and spread of leprosy. The relevance of the three epidemiological transitions to the frequency of leprosy since the transition to agriculture is also discussed. This is in tandem with extant modern and ancient leprosy genomic data. Ancient DNA evidence for the strains of the bacterium that affected people in the past is also furthering knowledge of the spread of leprosy. More work in this area is recommended, in concert with stable isotope analysis, providing information on the mobility and dietary histories of people in the past, and mitochondrial DNA to document ancestry. The historical evidence suggests that leprosy declined in the fourteenth century, but at the moment archaeological evidence is lacking to support such a hypothesis. Many reasons for this have been suggested (for example the plague, and improved diet and living conditions), but cross-immunity created by exposure to tuberculosis remains the strongest possibility. The two diseases have many characteristics in common, and tuberculosis and leprosy have been found together in skeletons in a number of instances. Co-infection with tuberculosis may be another hypothesis to consider as an explanation for leprosy’s decline.

The Bioarchaeological Evidence of Leprosy

This chapter explores the evidence for leprosy in skeletons from archaeological sites across the globe. On this basis, leprosy has a history of 7,000 years, but this picture will change as more evidence is uncovered. In the past, leprosy appears to have been a disease of the Old World and the northern and eastern hemispheres. The earliest skeletons with leprosy are from Britain, Hungary, Turkey, Iran, and Sudan. Northern Europe has the most evidence with Britain, Denmark, Hungary, and Sweden providing the most data. No evidence has been confirmed in the Americas, but there are more recent documentary data for leprosy there as a result of migration, the slave trade, and colonialism. Leprosy in non-adult skeletons is rare, and there is only one preserved body with evidence: an Egyptian mummy. The majority of the people whose skeletons revealed leprosy were buried normally for the time period in which they lived, their culture, and their geographic location. The bioarchaeological evidence does not corroborate the historical evidence for the frequency of leprosy (and some bioarchaeological evidence predates the historical data), nor does it support the wholesale stigma and marginalization of those affected that is often reported in the historical literature.

How Leprosy Affects the Human Body

This chapter considers how leprosy affects the human body. The skin, nerves, and upper respiratory system are affected. The bacillus can have a long incubation period, which means that many people may harbor the infection but will not show any signs, thus preventing early diagnosis and treatment. The variety of forms that leprosy can take shows how important the immune system is to the development of different leprosy types. This has consequences for the experience of each person with leprosy. The range of different types of skin lesions also reflect what a dynamic disease leprosy is, but the effect of the bacteria on the nervous system can lead to profound damage to the extremities in particular, damage that can have considerable consequences for the person concerned physically, socially, and mentally. Acute inflammatory episodes (reactions) provide a further challenge to people with leprosy and to health care workers helping to manage their patients’ infection.

The Biology of Leprosy Bacteria and How they are Transmitted to Humans

This chapter considers the nature of the bacterial causes of leprosy, Mycobacterium leprae and Mycobacterium lepromatosis, including research on their genomes. Paucibacillary leprosy is the high-resistance form of leprosy and multibacillary leprosy is the low-resistance form. It is clear that genomic research, including the documentation of different strains of the bacterium and identifying susceptibility and resistance genes, is providing knowledge that is helping to track transmission and identify areas within regions of countries that remain challenges for management. While it is concluded that leprosy is transmitted through the exhalation and then inhalation of bacteria-laden droplets (droplet infection), other reported mechanisms have been discussed, and there are environmental sources of the bacteria. Leprosy in children is rare, and males are affected more than females. The wide range of intrinsic (e.g., age, sex) and extrinsic (e.g., diet, living conditions) factors that make people more or less susceptible to leprosy provide a complex picture to manage when thinking about why any particular person contracts the infection. The wild nine-banded armadillo and the red squirrel natural endemic hosts for M. leprae, but while non-human primates may be affected there is no evidence of them being infected in the wild.