Molecular confirmation of Spirometra mansoni (Cestoda: Diphyllobothriidae) in Javanese keelback water snake (Fowlea melanzosta) in Indonesia.

Tapeworms of the genus Spirometra are important zoonotic parasites, yet their taxonomy remains unsettled and molecular species-level data from Indonesia are scarce. We examined plerocercoid larvae isolated from Javanese keelback water snakes (Fowlea melanzosta) collected in East Java, Indonesia. Infection prevalence in F. melanzosta was high (84 %), with 143 spargana recovered from subcutaneous tissues, musculatures, and the body cavities of 25 snakes. Morphological and histological features were consistent with Spirometra. Molecular analysis was used for accurate species-level identification. Partial mitochondrial cox1 sequences from five isolates were generated and analyzed phylogenetically. All sequences clustered unambiguously within the S. mansoni clade (PP = 0.99), alongside global reference isolates. Our analysis also reclassified a 2007 Indonesian isolate, previously assigned to S. erinaceieuropaei, as S. mansoni, retrospectively clarifying a misidentification. This study provides the first prospective molecular confirmation of S. mansoni in Indonesia, and underscores the role of semi-aquatic snakes in transmission cycles. These findings highlight the urgent need for expanded molecular surveillance and integrative taxonomy to clarify the epidemiology and zoonotic potential of Spirometra in the region.