OCCURRENCE OF EUSTRONGYLIDES EXCISUS (NEMATODA:DIOCTOPHYMATIDAE) IN EUROPEAN PERCH (PERCA FLUVIATILIS) AND GREAT CORMORANT (PHALACROCORAX CARBO) IN LAKE ANNONE, NORTHERN ITALY.

The genus Eustrongylides includes zoonotic nematodes that infect fish species and fish-eating birds of freshwater ecosystems. This study aimed to evaluate the occurrence of Eustrongylides in the paratenic host Perca fluviatilis (European perch) and in the definitive host, Phalacrocorax carbo sinensis (great cormorant), in Lake Annone, a shallow eutrophic lake located in the pre-mountainous area of the Alps in northwest Italy where wintering cormorants coexist with new breeding colonies. A total of 114 European perch and 48 cormorants were examined for the occurrence of Eustrongylides. All parasites collected were identified with microscopic examination and molecular analysis. Overall, 11 specimens of European perch (9.6%) and 13 individuals of cormorants (27%) harbored nematodes identified as fourth-stage larvae and adults of Eustrongylides excisus. The observed prevalence of Eustrongylides spp. appears to be intermediate between the higher values in cormorant breeding areas in northern Europe and the lower prevalence observed in their wintering sites in southernmost Europe. Considering the eutrophication status of freshwater ecosystems and the increasing population of the cormorants, Eustrongylides has an increasing potential range of dispersion in Europe, including Italy; thus an extensive surveillance should be carried out, especially given the zoonotic potential of this nematode.

Molecular identification of Contracaecum rudolphii A and B (Nematoda: Anisakidae) from cormorants collected in a freshwater ecosystem of the pre-alpine area in Northern Italy.

Contracaecum rudolphii (s.l.) is a complex of sibling species with different genetic structure and ecological preference. This study reports the presence of specimens of Contracaecum rudolphii (s.l.) from sedentary and wintering cormorants (Phalacrocorax carbo sinensis) from the pre-mountain area of the Alps in Northern Italy, an important crossroads for most of the bird migration routes. A total of 48 specimens of cormorants collected from two adjacent freshwater habitats were analysed and C. rudolphii nematodes were retrieved in 100% of the examined specimens. A subsamples of 115 C. rudolphii individuals were genetically characterized and found to belong to the sibling species C. rudolphii B (n = 90) and C. rudolphii A (n = 25). C. rudolphii B were retrieved from both locations and included adults as well as larvae, while only adults of C. rudolphii A were detected, and in just one location. As expected for a freshwater environment, C. rudolphii B constitutes the largest sibling fraction, indicating that this likely is the endemic species, while cormorants originating from the breeding brackish lagoons and marine coastal environments of central and northern Europe could have brought C. rudolphii A from their breeding sites or migration stopovers.