The infection of great cormorants (Phalacrocorax carbo sinensis L., 1758) with Contracaecum rudolphii (Nematoda: Ascaridoidea) in the district of Upper Bavaria (Germany) and the canton St. Gallen (Switzerland)

In cormorants (Phalacrocorax carbo sinensis L., 1758; n = 50) shot to scare them away from fish ponds in the district of Upper Bavaria high abundance (96,3) and prevalence (100%) of Contracaecum rudolphii (Nematoda: Ascaridoidea) was observed as well as in cormorants (n = 50) shot in the canton of St. Gallen (63,3 and 94%). The varying intensity is attributed to the different origin of the cormorants. No negative clinical signs in the cormorants were ascertained. Presumably a highly infected host is damaged seriously due to the feeding of C. rudolphii on the host's tissue in the case of reduced food availability. A coprological investigation carried out by flotation procedure refers to an intermittent excretion of eggs during the summer and winter. In vitro, larvae (L 2) hatching from eggs stay infectious in freshwater for at least 13 days. The common freshwater copepod Cyclops abyssorum praealpinus is infected by L 2 of C. rudolphii. Thus this copepod belongs to the first intermediate hosts. Cormorants shot during the summer at Lake Chiemsee (D) (n = 13) showed statistically significant lower abundance and prevalence (19,4 and 85%) of C. rudolphii compared to birds shot last winter in the same region. Presumably the occurrence of C. rudolphii in these birds indicates that fishes of Lake Chiemsee or nearby bodies of water are also infected with larvae of C. rudolphii. The presence of the parasite was not reported previously in these localities. Further investigation are needed particularly regarding to possible pathogenic effects on fishes and the public health question.