When discovery meets neglect: rethinking disease emergence in cutaneous leishmaniasis and other neglected tropical diseases

Recent reports of Leishmania donovani causing cutaneous leishmaniasis (CL) in Nepal have revived a key question in disease ecology: when does a disease truly emerge, and when is it simply newly recognized? Apparent emergence likely reflects underdiagnosis rather than parasite evolution. These cases have likely gone unnoticed because surveillance programs and clinical awareness have historically centered on VL in this L. donovani –endemic region. As leishmaniasis expands into previously non-endemic areas, physicians encountering unfamiliar lesions are prompted to investigate and identify the etiological agent, revealing not a new parasite variant, but the geographic and diagnostic expansion of a known one previously unrecognized by the healthcare system. Epidemiological “emergence,” in this context, stems less from parasite evolution than from the intersection of changing disease ecology, improved diagnostics, and shifting clinical attention. We hypothesize that cutaneous leishmaniasis due to L. donovani in Nepal represents a detection-driven phenomenon rather than a novel biological event.