Integrated morphological, molecular, and immunopathological characterization of Raillietina hymenolepidoides from Psammomys obesus reveals potent in vitro anthelmintic activity of Androctonus crassicauda venom

Rodent-borne cestodes of the genus Raillietina include several poorly characterized species with potential zoonotic relevance, yet their molecular identity, host–parasite interactions, and susceptibility to alternative anthelmintic agents remain inadequately understood. Here, we present an integrated morphological, ultrastructural, molecular, immunopathological, and experimental evaluation of Raillietina hymenolepidoides naturally infecting the fat sand rat (Psammomys obesus) in Egypt. Adult cestodes were identified using light microscopy, scanning electron microscopy, and mitochondrial cytochrome c oxidase subunit I (COI) sequencing, confirming species identity and revealing close phylogenetic affinity to Raillietina mahnerti. Histopathological analysis of infected hosts demonstrated severe intestinal epithelial degeneration, necrosis, and Peyer’s patch hyperplasia, accompanied by pulmonary emphysematous changes. Immunohistochemical profiling revealed increased CD56⁺ natural killer cell infiltration alongside reduced CD68⁺ macrophage and TGF-β expression, indicating altered local immune regulation during chronic infection. In parallel, the in vitro anthelmintic activity of Androctonus crassicauda crude venom was assessed against adult cestodes, revealing time-dependent tegumental disruption, microtriche erosion, proglottid detachment, and parasite death, as visualized by scanning electron microscopy. Collectively, these findings provide the first comprehensive molecular confirmation of R. hymenolepidoides in P. obesus in Egypt and demonstrate the pronounced in vitro cestocidal effects of scorpion venom. The study highlights the value of integrative parasitological approaches and supports further investigation of venom-derived compounds as potential leads for novel anthelmintic development.