Leishmaniasis is a parasitic disease caused by protozoa of the genus Leishmania, transmitted to humans through the bite of infected female sandflies. This disease represents a global public health challenge, impacting millions worldwide. Understanding its geographical distribution is an important step in controlling and preventing its spread.
Global Geographic Patterns
Leishmaniasis manifests in several forms, each with distinct geographical patterns. Visceral leishmaniasis (VL), also known as kala-azar, is the most severe form, often fatal if left untreated, and is characterized by fever, weight loss, and enlargement of the spleen and liver. In 2023, about 83% of global VL cases were reported from seven countries: Brazil, Ethiopia, India, Kenya, Somalia, South Sudan, and Sudan.
Cutaneous leishmaniasis (CL) is the most common form, causing skin lesions and ulcers, primarily on exposed body parts. The Eastern Mediterranean Region accounts for approximately 80% of reported cutaneous leishmaniasis cases worldwide. In 2023, six countries—Afghanistan, Algeria, Brazil, Pakistan, Peru, and the Syrian Arab Republic—together accounted for 83% of global reported CL incidence.
Mucocutaneous leishmaniasis (ML) is a destructive form affecting mucous membranes in the nose, mouth, and throat. Over 90% of mucocutaneous leishmaniasis cases occur in Bolivia, Brazil, Ethiopia, and Peru. Leishmaniasis is endemic in 99 countries and territories as of 2022, with most experiencing both VL and CL forms, while others have only one.
Environmental and Socioeconomic Influences
Environmental factors play a significant role in shaping the distribution of leishmaniasis. Climate variables such as temperature, rainfall, and humidity directly affect the life cycle and activity of sand fly vectors. Small changes in temperature can affect sand fly development and metabolism, as well as parasite development within the vector, potentially enabling transmission in new areas.
Land cover changes, including deforestation, urbanization, and agricultural practices, also contribute to the disease’s spread. Deforestation can create new favorable habitats for sand fly reproduction and promote closer contact between humans, vectors, and animal reservoirs. This environmental modification can lead to the urbanization of diseases historically considered rural.
Socioeconomic factors are intertwined with the disease’s prevalence and impact. Poverty is a primary risk factor, often leading to inadequate housing conditions that provide resting and breeding sites for sandflies. Malnutrition and weak immune systems, frequently associated with poverty, further increase vulnerability to infection and complicate treatment outcomes.
Population movements, such as migration and displacement, also contribute to the spread of leishmaniasis by introducing the disease into new areas. The lack of access to proper sanitation and healthcare facilities further compounds the problem, creating environments conducive to transmission and hindering early diagnosis and treatment.
Utilizing Maps for Public Health
Maps are useful tools in public health efforts to combat leishmaniasis. These maps are often generated using geographic information systems (GIS), which integrate data from various sources. This process allows for the creation of high-resolution, evidence-based risk maps.
These maps are useful in identifying high-risk areas, allowing public health officials to target surveillance efforts. By visualizing disease patterns, resources can be allocated to regions, optimizing interventions. For example, specific areas can be identified for vector control measures, active case detection, and provision of treatment.
Maps also serve to inform travelers about potential risks, contributing to personal prevention strategies. Monitoring disease trends through mapping helps assess the impact of control programs and adapt strategies. This spatial analysis supports decision-making and planning for vector-borne disease control.