Occurrence and Spatial Distribution of (Cestoda: Diphyllobothriidea) in Lake Iseo (Northern Italy): An Update.

(Linnaeus, 1758) (Cestoda: Diphyllobothriidea; syn. ), is a fish-borne zoonotic parasite responsible for diphyllobothriasis in humans. Although has long been studied, many aspects of its epidemiology and distribution remain unknown. The aim of this study was to investigate the prevalence, mean intensity of infestation, and mean abundance of plerocercoid larvae of in European perch () and its spatial distribution in three commercial fishing areas in Lake Iseo (Northern Italy). A total of 598 specimens of were caught in 2019. The total prevalence of was 6.5%. However, there were significant differences between areas (10.2% North; 7.3% Center; 1.5% South) (Chi-square test, = 0.0018). The mean intensity of infestation ranged from 1 larva in southern area to 1.2 larvae in both the central and northern (Pisogne) areas. In addition, the mean abundance ranged from 0.02 in the southern area to 0.26 in the northern area (Pisogne). The total number of larvae (anterior dorsal-AD = 21; anterior ventral-AV = 1; posterior dorsal-PD = 15; posterior ventral-PV = 5) differed significantly between the four anatomical quadrants (Kruskal-Wallis test; = 0.0001). The prevalence of plerocercoid larvae in European perch from Lake Iseo has long been investigated, but without an appropriate sampling design. With the present study, a broader analysis in spatial distribution has been added to the existing literature, revealing new information about distribution and occurrence in Lake Iseo, with new data that will be useful for health authorities and future studies.