Experimental transmission of Otostrongylus circumlitus (Railliet, 1899) (Metastrongyloidea: Crenosomatidae), a lungworm of seals in eastern arctic Canada

Abstract

The transmission of few metastrongyloids infesting marine mammals is known. The results of experimental infections using Otostrongylus circumlitus (Crenosomatidae), a lungworm of pinnipeds, suggested that this metastrongyloid uses fish as intermediate hosts. Various marine organisms (crustaceans, molluscs, and fish) were exposed to first-stage larvae from naturally infected young-of-the-year ringed seals (Phoca hispida) from northern Quebec (Salluit). The first and second moults occurred 3 and 56 days post exposure in the mucosa and muscularis of the intestine of American plaice (Hippoglossoides platessoides) kept at 4 °C. Third-stage larvae were found under the intestinal serosa. Attempts to infect invertebrates were unsuccessful. Transmission to seals may occur from mid-June through the autumn as young seals start feeding intensively on invertebrates and fish. First-stage larvae leave the lungs via the bronchial escalator and are swallowed and released into the sea with the faeces of seals, where they would be available to benthic or pelagic fish. The morphology of the first three larval stages is described.