Abstract

The biology of the lungworm, Otostrongylus circumlitus, previously poorly studied has been now studied in the field and laboratory. This large parasitic nematode found in the bronchi and bronchioles can be obstructive causing inflammation and stimulating abundant mucus production. Secondary bacterial infections are reported. This parasite is of significance to northern native peoples who depend on seals as food and to rehabilitation centers treating stranded seals. Field data has shown that this lungworm infects most phocid seals including harbour, ringed, grey, hooded, bearded, spotted, Baikal, ribbon, and northern elephant seals. The latter species appears to be poorly adapted to this parasite, which may suggest a recent association. Distribution of O. circumlitus is circumpolar. Prevalence in infected seals ranges from 10 to 89% with infections involving predominantly young-of-the-year or age=O animals. Young stranded animals are often heavily infected. Mean intensities reported from stranded and hunted animals are usually 9-58 but can range up to 280 worms. Laboratory work has demonstrated that invertebrates are not required in the life cycle as intermediate hosts, but they could serve as paratenic hosts. First-stage larvae passed in the faeces of infected seals are infective to fish, encapsulating in the intestinal wall and developing to the third stage, which is infective to seals. Grey seals were exposed to third-stage larvae from experimentally infected fish in order to study development, pathogenesis and migration to the lungs. Preliminary results of this work currently in progress will be presented.