Leprosy: Outbreak And Eradication

The history of leprosy is a fascinating, and yet unfortunate one. This disease, also known as Hansen's disease, has been around for thousands of years and has been described in ancient texts from China, India, and Egypt. It's caused by a bacterium called Mycobacterium leprae and it affects the skin, nerves, and mucous membranes. However, the exact time when the disease came into existence is not yet known.
 
Based on the ancient texts available from China and India where it was called “Kushta” which has the mentioned symptoms of Leprosy and the texts date back to 500 BC and 600-1400 BC respectively.
 
It has been however a subject of great interest for scientists over the years to understand how the communicable disease Leprosy had begun, spread across continents, and at one time was rampant. Equally fascinating is, how it had declined over time on its own even before modern medicine came into existence.
 
In this article instead of discussing the regular old subject of the symptomatology and pathophysiology of leprosy, we take you on a journey through time to understand the history of its beginning and decline over time. A true accomplishment of medicine and humans is what you get to read through this article. 
 

History of Leprosy

 
In the past, people considered leprosy a curse or punishment of god. People affected by it were often shunned by society and forced to live in leper colonies or designated areas. The disease was also associated with moral decay and sin; people believed it was contagious and could be spread through touch or bodily fluids.
 
There is always a debate about the origin of Leprosy, whether it was in Eastern Africa or India and there is still a certain degree of uncertainty in this subject. Although initially the disease was confined only to certain areas, as it was believed that the spread of Leprosy centuries ago was either due to trade or the invasion of foreign rulers.
 
One such example cited in history is that of Alexander the Great’s raid in India and the spread of Leprosy to Greece as mentioned by a Greek physician in his texts, who then named the disease elephantiasis Graecorum. Through the years, leprosy had spread across the Mediterranean and Western Europe by the Romans and other such invasions.
 
Even though there are chances that the conditions at the time could have been misdiagnosed, the skeletal findings of those times had features of true leprosy. Certain skeletal remains were found of maxillary and nasal spine erosions, which are found in conditions of facies leprosa, that indicate the presence of true leprosy in those times and that it was indeed rampant. 
 
The spread to Western Africa and other western countries could have possibly occurred due to the slave trade and migration of population, which had taken place around 500-600 years ago. Even genomic studies have suggested that the transmission of Leprosy was a result of the migration of populations from the Far East to Pacific islands around the 19th century.
 

Leprosy in Modern Era

It wasn't until the 19th century that leprosy began to be studied scientifically, and in 1873, a Norwegian physician Dr. Gerhard Armauer Hansen identified the bacterium that causes the disease. This discovery led to the development of diagnostic tests and treatments for leprosy. In the 1940s, the drug dapsone was introduced as a treatment for leprosy, and in the 1980s, multidrug therapy (MDT) was developed, which effectively treated leprosy and significantly reduced the number of people affected by the disease. By the mid-1980s, the global disease burden was estimated to be between 10 and 12 million patients, with 122 countries reporting endemic cases of leprosy to WHO.
 
In 1991, the World Health Organization (WHO) launched a Global Leprosy Programme intending to eliminate leprosy as a public health problem. The program was based on the strategy of early detection and treatment of leprosy, and it focused on reaching out to people affected by the disease in remote and hard-to-reach areas. The program also aimed to reduce the stigma and discrimination associated with leprosy to provide rehabilitation and support services for people affected by the disease.
 
After a point of time, there was indeed a decline in the cases of Leprosy after medical advancements took place. The studies of the genomics of the bacilli made it easier to develop drugs to combat the disease on a large scale. However, this ended when in the 1970s there was a relapse of Leprosy cases due to drug resistance to dapsone around by 19% of the cases.

The WHO, then, endorsed multidrug therapy (MDT) protocols comprising rifampin, clofazimine, and dapsone in the treatment of Hansen’s Disease (HD/Leprosy) in 1982. Patients with the paucibacillary disease would be treated for six months, while those with the multibacillary disease would be treated for 12-24 months. The response to MDT treatment was positive, with a relapse rate of 1% for multibacillary illness and slightly more than 1% for paucibacillary disease. The increased confidence that the illness may be controlled led to the World Health Assembly's 1991 declaration of a goal to "eradicate leprosy as a public health hazard," defined as lowering the global prevalence of HD to one case per 10,000 people by the year 2000.
 

Epidemiology of Leprosy

Even though the science had advanced very little had been known so far about the source, transmission, susceptibility, and pathogenesis of the disease by the 1990s making it a challenge to achieve the goal set by the WHO to eliminate Leprosy. Even to date most research papers even though thorough studies are unable to establish these facts.

Here is what is known so far about the disease:

• 1. Mycobacterium leprae grows slowly, doubling every 11 to 13 days. It is an obligatory intracellular parasite that thrives at temperatures ranging from 27° to 30° C.
     
  2. Human skin, peripheral nerves, nasal mucosa, upper respiratory tract, and eyes are typically key target organs of the disease.
     
  3. Humans are assumed to be the disease's natural reservoir, with an average incubation period of three to five years.
     
  4. The disease has been found in wild armadillos in the southern United States, as well as three species of nonhuman primates (chimpanzees, cynomolgus macaques, and sooty mangabey monkeys), but these are not regarded to be significant sources of human disease.
     
  5. The mode of transmission is unknown; however, the ulcerated nasal mucosa of multibacillary patients can produce more than 10 million live bacilli each day, indicating that transmission by respiratory droplet dissemination is possible.
     
  6. Additionally, organisms have been found to survive for up to nine days outside of the human host under tropical conditions, raising the possibility of contact spread through broken skin. The possibility of the disease being spread through insect vectors also cannot be definitively excluded.
     
  7. A great deal is also unknown regarding illness susceptibility and causation. More than 95% of persons have an inbuilt resistance to disease development following exposure.
     
  8. M. leprae's unusual ability to survive within Schwann cells of peripheral nerves as well as macrophages. The bacterium is extremely low in pathogenicity and is essentially harmless to tissues.
     
  9. In HD, there are two sorts of immunological reactions. Type 1 is a delayed-type hypersensitivity reaction, while Type 2, erythema nodosum leprosum, is regarded to be an immunologically complex illness. The reasons that cause these immune responses are unknown, and the reactions might occur during the normal course of untreated disease, during antimicrobial therapy, or after the antimicrobial "cure" of the infection has been completed. If the reactions are not treated medically, the patient will suffer persistent sensory, motor, and/or autonomic peripheral or other nerve damage, which could lead to severe handicap.
     
  10. The absence of a simple and effective screening tool for identifying individuals or communities with subclinical disease or asymptomatic infections still poses a challenge to public health. 

Over the last two decades, the reported global prevalence of active HD infection has decreased by over 90%. 18 The lack of a commensurate decline in disease incidence is cause for concern. From 1994 through 2003, the yearly new case detection rate was consistently greater than 500,000 new cases per year.
 

Risk of relapse

While progress in treating HD is being celebrated, there is a risk that this progress will diminish the perceived benefit of continuing to spend resources on HD, as other competing priorities (e.g., human immunodeficiency virus/acquired immunodeficiency syndrome, malaria, and tuberculosis) may appear to be of relatively greater importance. The resurgence of drug-resistant tuberculosis in the United States after public health resources were diverted to other priorities may be instructive of the need to continue devoting adequate resources to a communicable disease that has currently left one million to two million people worldwide with permanent disabilities.
 
It is important to remember that managing this condition entails both treating the bacterial infection and limiting the risk of persistent nerve damage and consequent disability.
 
Furthermore, whether success can result in a paradoxical delay in therapy and an increase in the severity of impairment should be evaluated. As a sickness or condition gets increasingly rare, a treating physician must have a higher level of suspicion to properly diagnose or refer a patient for care.
 
Even though we've come a long way in eradicating leprosy, the disease still exists in some countries, particularly in Africa and Asia, where it's often found in remote and hard-to-reach areas. Additionally, the disease still carries a significant social stigma, and people affected by leprosy continue to face discrimination and marginalization.
 

Conclusion:

HD continues to be riddled with paradoxes. It is one of the oldest diseases known to man and the first human bacterial pathogen discovered; nonetheless, significant gaps in our fundamental understanding of this disease remain in comparison to other infectious diseases. More than 95% of the population possesses a natural resistance to the disease, current antibiotic treatment is available to remove a patient's infection, and early treatment can prevent or significantly reduce the disease's repercussions. Nonetheless, there are many cultural misconceptions, superstitions, and stigmas connected with HD that prevent early detection and treatment-seeking behavior.
 
Despite several challenges, significant progress has been made in giving treatment to millions of people and combating social stigma and misinformation. 22,23 Hopefully, the progress made thus far will be maintained and advanced by governments' continued political will, ongoing research into the basic understanding of the disease and improved treatments or vaccines, and maintaining a high index of suspicion in both the public and medical communities that HD might be a treatable cause of a patient's condition. If this is the case, there is a chance that HD will no longer be one of the top causes of physical disability in the world.
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If you are an MBBS or MD graduate/ intern or you are a Microbiologist you are eligible for this course and it would be of much more interest to you if you loved what you read so far. 
 

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