Molecular identification, life cycle and histopathology of Contracaecum rudolphii infecting Phalacrocorax carbo sinensis in northern Italy

Six freshly dead adult great cormorant Phalacrocorax carbo sinensis (Blumenbach, 1798) were collected during the winter season of 2025 from the coast of Canneviè lagoon (Northern Adriatic Sea, Italy).All 6 P. carbo sinensis (prevalence 100%) were infected with nematodes of the genus Contracaecum Raillet and Henry, 1912 with the intensity of infection ranging from 39 to 550 worms per host (212.8 ± 80.7; mean ± S.E.).From the same lagoon, 41 European seabass, Dicentrarchus labrax (L.) were examined for helminths and in 27 specimens (65%) L3 larvae of C. rudolphii were encountered in extraintestinal sites of the seabass.In this study, 40 adults and 30 larvae of C. rudolphii from cormorants and 40 nematode larvae from seabass were characterized at species level using the diagnostic key based on the RFLP of two ribosomal regions, the nuclear ITS and the mitochondrial rrnS https://doi.org/10.