Introduction

Leprosy, also known as Hansen’s disease, is a chronic infectious disease caused by Mycobacterium leprae. It primarily affects the skin and peripheral nerves and is characterised by a long incubation period and slow progression. Despite global efforts to control and eliminate the disease, the occurrence of leprosy in children remains a significant public health concern, particularly in endemic regions. The emergence of new paediatric cases is a sensitive indicator of ongoing community transmission and reflects the gaps in early detection and prevention strategies.¹

How is leprosy transmitted?

Leprosy is primarily transmitted through prolonged and close contact with individuals who have untreated multibacillary (MB) leprosy. This is likely via respiratory droplets released during bouts of coughing or sneezing. The risk of transmission increases when a child lives in a household or community with undiagnosed or untreated leprosy patients. The incubation period of leprosy can range from several months to more than a decade, making it difficult to trace the exact source of infection. In children, the incubation period is generally shorter due to their developing immune systems.²

Respiratory droplets

As mentioned before, the most widely accepted theory is that leprosy is transmitted from person to person through prolonged and close contact. The inhalation of airborne droplets containing M. leprae is the most likely pathway. These droplets are released when an infected person—particularly someone with untreated multibacillary (MB) leprosy—coughs, sneezes or speaks.³

Once inhaled, the bacteria may lodge in the mucosal linings of the nose or upper respiratory tract of the exposed individual. Over time, if the individual’s immune system is unable to contain the infection, the bacteria may spread and cause clinical disease. However, it is important to note that not everyone exposed to M. leprae becomes infected, and only a small percentage of those infected go on to develop the disease. This is due to the individual's immune response, which plays a critical role in determining susceptibility.³

Prolonged exposure

Unlike many contagious diseases, leprosy is not highly infectious. Short-term or casual contact-such as shaking hands, sharing utensils, or sitting next to someone with leprosy generally does not usually result in transmission. Instead, sustained exposure over months or years is typically required for someone to become infected. This is why household contacts, particularly those who live in crowded and poorly ventilated settings, are at a higher risk.³

Children are often infected by close family members, especially if an adult in the household has undiagnosed and untreated leprosy. The risk is further amplified in communities where awareness is limited, health infrastructure is inadequate, and delays in treatment are prevalent.³

Skin-to-skin contact

Although less significant compared to the respiratory route, there is some evidence to suggest that direct skin contact, particularly through broken skin or wounds, may pose a risk in rare cases. M. leprae can be found in skin lesions of infected individuals; in environments with poor hygiene, this could theoretically contribute to transmission. However, such cases are considered uncommon and not the primary mechanism of spread.³

Environmental reservoirs

Another area of scientific investigation is the potential role of environmental reservoirs in leprosy transmission. Some studies have isolated M. leprae from soil and water sources, especially in regions with high disease prevalence. While it's not definitively proven that people contract leprosy through environmental exposure, the possibility exists and is being actively explored.⁴

Additionally, certain animal species have been identified as natural hosts of M. leprae. For example, in the southern United States, nine-banded armadillos have been found to carry the bacterium and, in rare cases, can transmit it to humans. In some parts of Asia, red squirrels have also been identified as carriers. These rare zoonotic transmissions suggest that leprosy transmission may be more complex than previously believed, involving potential non-human reservoirs in certain ecological contexts.⁴

The role of asymptomatic carriers

Another critical consideration in the understanding of transmission is the role of asymptomatic carriers—individuals who harbour the bacterium without exhibiting clinical signs of disease. These carriers can unknowingly spread the infection, particularly in endemic areas.²

Asymptomatic individuals may remain undiagnosed for years, maintaining a silent reservoir of M. leprae within communities and making eradication efforts more difficult.²

This phenomenon is especially important in the context of children, who may be exposed to such carriers in both household and school environments, thus increasing their vulnerability.²

Socioeconomic and environmental factors

Transmission of leprosy is also influenced by broader social determinants of health, including:

• Poverty and overcrowding, which facilitate close contact and limit access to hygiene and healthcare
• Lack of education and awareness, which delays diagnosis and treatment
• Inadequate public health infrastructure, which hinders surveillance and prevention

In areas where these factors are prevalent, leprosy continues to spread silently, particularly affecting vulnerable groups like children.

Children as vulnerable hosts

Children are particularly susceptible to infection due to several reasons:¹

• Close contact with adults, especially parents or grandparents, who may have untreated or undiagnosed leprosy
• Immature immune systems, which make them more vulnerable to infections
• Lack of awareness among caregivers or healthcare providers about early signs of leprosy in children

Transmission to children often occurs silently within the home or local community, and signs may not appear until months or years later. The detection of a case in a child is therefore considered strong evidence of recent, ongoing transmission.¹

Common sources of infection in children

The most common source of infection is a close family member with untreated leprosy. Studies have shown that children living with MB leprosy patients have a significantly higher risk of acquiring the disease.¹

In endemic areas, children can also be infected through repeated contact with neighbours, teachers, or peers who may be asymptomatic carriers or undiagnosed patients.¹

Adult leprosy cases that go unrecognised or are treated late can serve as hidden reservoirs for community transmission, impacting children disproportionately.¹

Signs of leprosy in children

In children, early signs of leprosy can be subtle and are often misdiagnosed:⁵

• Hypopigmented or reddish skin patches with reduced sensation
• Tingling, numbness, or weakness in limbs
• Thickened nerves
• Ulcers or wounds on hands or feet that don’t heal
• Facial involvement (e.g., lagophthalmos or nasal stuffiness)

When diagnosis is delayed, children are at increased risk of developing nerve damage and disability — consequences that can persist for life if not addressed early.⁵

Preventing transmission in children

Early detection and treatment

Prompt diagnosis and treatment of leprosy cases, particularly in adult household members, significantly reduces the risk of transmission to children. The World Health Organization (WHO) recommends multidrug therapy (MDT) for all confirmed cases, which is effective in curing the disease and preventing further transmission.⁶

Contact tracing

Whenever a new leprosy case is diagnosed, close contacts, especially children, should be screened and monitored. In many countries, preventive therapies (such as single-dose rifampicin) are offered to eligible contacts.⁶

Community education and awareness

Educating communities about the signs, symptoms, and curability of leprosy helps reduce stigma and promotes early care-seeking behaviour. Parents and caregivers should be encouraged to bring children with suspected skin lesions for medical evaluation.⁶

School-based screening programs

In endemic regions, school health initiatives can help identify cases early by screening students for skin patches and nerve involvement.⁶

Vaccination and prophylaxis

While there is no specific vaccine for leprosy, the BCG vaccine (primarily used against tuberculosis) provides some protection against M. leprae. Ongoing research on vaccines and chemoprophylaxis may provide additional tools for prevention in the future.⁶

Summary

The transmission of leprosy in children highlights the need for sustained public health vigilance, especially in endemic regions. Paediatric cases not only reflect the failure to interrupt transmission chains but also identify vulnerable populations that require targeted interventions. Through early detection, effective contact tracing, community education, and comprehensive treatment, we can significantly reduce and eventually eliminate leprosy transmission among children.