Leishmaniasis Epidemiology and Immune Responses

Leishmaniasis encompasses a spectrum of parasitic diseases transmitted by phlebotomine sand flies, presenting primarily as cutaneous, mucocutaneous or visceral forms. Endemic foci span tropical and subtropical regions, with over one billion people at risk and up to one million new cases annually. Ecological and climatic changes, population movements and conflict drive shifting transmission patterns. In many areas, zoonotic cycles involving domestic dogs and wild reservoirs complicate control efforts. Parasite diversity and hybridisation events fuel local adaptation and can influence spread of co-infections, including persistent viral agents within Leishmania cells. Upon inoculation, promastigotes are taken up by resident macrophages and dendritic cells; the ensuing innate response, shaped by cytokines and chemokines, determines parasite survival or destruction. A Th1-polarised adaptive response, featuring interferon-γ and interleukin-12, is generally protective, whereas Th2 or regulatory profiles favour persistence. Tissue-resident macrophages can form immune niches that dictate lesion outcome, and excessive inflammation contributes to pathology. Limited chemotherapeutic options and emerging resistance underscore the need for vaccine development and novel diagnostics. Recent advances in experimental human infection models and spatial transcriptomics provide unprecedented insight into immune microenvironments, while studies of parasite–virus symbiosis reveal potential modifiers of disease severity and transmission dynamics.

Research from Nature Portfolio

Recent studies have established a controlled human infection model for cutaneous disease, where deliberate sand-fly transmission of Leishmania major in healthy volunteers yielded consistent lesion development and allowed mapping of local immune cell distribution. Spatial transcriptomic analysis within biopsy specimens defined discrete immune niches, highlighting how cytokine gradients and cell subsets organise around parasite foci. This platform now serves as a benchmark for evaluating vaccine candidates and dissecting correlates of protection. In parallel, molecular epidemiological work in South American rainforests has demonstrated that hybridisation among Leishmania braziliensis populations correlates with increased prevalence and diversity of endogenous dsRNA viral particles. Such symbioses appear to amplify parasite dissemination and may exacerbate clinical outcomes, revealing an ecological mechanism by which population genetics influences epidemiology and immune evasion.

Leishmaniasis Epidemiology and Immune Responses publication trend

The graph below shows the total number of articles in leishmaniasis epidemiology and immune responses across all publications each year (not limited to Nature Index journals).

Technical terms

Controlled Human Infection Model: A research framework in which volunteers are deliberately exposed to a pathogen under controlled conditions to study disease mechanisms and evaluate interventions.

Spatial transcriptomics: A technique that maps gene expression within tissue sections, preserving spatial context to reveal local cellular interactions.

Metacyclic promastigote: The infective, flagellated form of Leishmania transmitted by sand flies.

Hybridisation (parasite genetics): The interbreeding of distinct Leishmania strains or species, resulting in genetic exchange and novel genotypes.

Cytokine: A signalling protein secreted by immune cells that modulates the intensity and nature of immune responses.

References

1. Safety and reactogenicity of a controlled human infection model of sand fly-transmitted cutaneous leishmaniasis. Nature Medicine (2024).
2. Diversity and dissemination of viruses in pathogenic protozoa. Nature Communications (2023).
3. Drug resistance and treatment failure in leishmaniasis: A 21st century challenge. PLOS Neglected Tropical Diseases (2017).
4. Leishmaniasis Worldwide and Global Estimates of Its Incidence. PLOS ONE (2012).
5. LeishVet guidelines for the practical management of canine leishmaniosis. Parasites & Vectors (2011).
6. The early interaction of Leishmania with macrophages and dendritic cells and its influence on the host immune response. Frontiers in Cellular and Infection Microbiology (2012).
7. Seasonal Dynamics of Phlebotomine Sand Fly Species Proven Vectors of Mediterranean Leishmaniasis Caused by Leishmania infantum. PLOS Neglected Tropical Diseases (2016).