Leishmania (Mundinia) martiniquensis beyond Southeast Asia: Molecular, clinico-pathological and entomological evidence of an emerging visceral leishmaniasis focus from Sri Lanka, South Asia.

The subgenus Leishmania (Mundinia) is a recently recognized, phylogenetically distinct lineage whose species cause visceral, cutaneous and disseminated leishmaniasis, but autochthonous human transmission has been molecularly confirmed in only a few settings worldwide. This reports an integrated molecular, histopathological and entomological investigation of a 66-year-old Sri Lankan man with pancytopenia, hepatosplenomegaly and prolonged fever of initially unclear aetiology. Species identification used three molecular markers, the 18S ribosomal RNA gene, the ITS1 region and the heat shock protein 70 (HSP70) gene, followed by Sanger sequencing, BLASTn analysis and maximum likelihood phylogenetic reconstruction; a structured entomological survey combining cattle-baited net trapping, indoor hand collection and sticky trapping was conducted around the patient's residence over four months. Histopathology demonstrated Leishmania amastigotes within lymph node histiocytes and tingible body macrophages. All three markers concordantly identified L. martiniquensis, with greater than 99% nucleotide identity to reference sequences and phylogenetic support of 59% - 100% bootstrap values (GenBank accessions PQ727038, PZ578091 and PZ393726). The patient's travel history excluded exposure to any previously recognized endemic region, supporting autochthonous acquisition. Entomological surveys identified Phlebotomus argentipes and Sergentomyia zeylanica near the residence, with habitats consistent with established sand fly transmission ecology. The patient achieved full clinical recovery following intravenous amphotericin B therapy. This case provides molecular evidence of L. martiniquensis transmission outside its previously recognized endemic range, indicating that the geographic distribution of subgenus Mundinia is broader than appreciated, with implications for leishmaniasis surveillance, diagnostic algorithms and vector-borne disease research across South Asia and beyond.