Rev 05/07/2026
Chromadorea
Rhabditia
Rhabditida
Metastrongyloidea
Crenosomatidae
Type species of the genus: Otostrongylus circumlitus (Railliet, 1899) de Bruyn, 1933
Synonyms
Males:
Females:
Ref:
Otostrongylus circumlitus, a circumpolar metastrongyloid nematode, is primarily a parasite of seals (Onderka, 1989; Kelly et al., 2005)
Food Sources and Feeding strategies for the genus Otostrongylus
The type (and only) species, O. circumlitus is a lungworm parasite of seals (Phoca spp) and sea lions (Zalophus spp.). Less ferquently its is reported from gray (Halichoerus grypus), harp (Pagophilus groenlandicus), and hooded (Cystophora cristata) seals (Delyamure, 1968; Anderson et al., 1974; Lucas et al., 2003; Kelly et al, 2005).. The parasite is also reported asan important parasite of juvenile northern elephant seals (Mirounga angustirostris) and Pacific harbor seals (Phoca vitulina richardsi) along the central coast of California (Gulland et al., 1997; Kelly et al., 2005).
An infected sea lion was emaciated and had diarrhea. There were multiple areas of hemorrhage throughout all lung lobes. Males and females of O. circumlitis were collected from pulmonary arteries. In contrast, in most Phoca spp., adult nematodes typically found in the bronchi and bronchioles (Kelly et al., 2005).
In the relationship between O. circumlitus and other phocid species, there is rather minor host reaction to immature stages, suggesting long term coevolution of host and parasite. The severe reaction to immature O. circumlitus by northern elephant seals during the prepatent period may suggest that the relationship between the northern elephant seal and O. circumlitus is a more recent host-parasite association (Gulland et al., 1997; Kelly et al., 2005).
Life cycle is indirect. First stage larvae develop in several fish species but, in experimental infections, only American plaice (Hippoglossoides platessoides) supported development of infective larvae (Bergeron, 1997)..
Two of the definitive host species, northern elephant seals and Pacific harbor seals, are sympatric with the California sea lion (Zalophus californianus) throughout its California range (Kelly et al., 2005).
Andesron, S., Bonner, W.N., Baker, J., Richards, R. 1974. Grey seals, Halichoerus grypus of the Dee Estuary and observations on characteristic skin lesions in British seals. Journal of Zoology 174: 429-440.
Bergeron, E., Measures, L.M., Huot, J. 1997. Experimental transmission of Otostrongylus circumlitus (Raillet, 1899) (Metastrongyloidea: Crenosomatidae) a lungworm of seals in eastern arctic Canada. Canadian Journal of Zoology 75: 1364-1371
Delyamure, S. 1968. Helminthofauna of marine mammals (ecology and phylogeny). Academy of Sciences of the USSR Laboratory of Helminthology. Israel program for scientific translations, U.S. Department of the Interior and the National Science Foundation, Washington, D.C. IPST Cat. 1886 TT 67-51202, 522 pp.
Gulland, F.M.D., Beckmen, K.,Burek, K., Lowenstine, L., Werner, L. Spraker, T., Daily, L., Harris, E. 1997. Nematode (Otostrongylus circumlitus) infestation of northern elephant seals stranded along the central California coast. Marine Mammal Science 13: 446-459.
Kelly, T.R., Craig, D., Colegrove, K.M., Lowenstine, L.J., Dailey, M., Gulland, F.M. Haulena, M. 2005. Metastrongyloid Nematode (Otostrongylus circumlitus) Infection in a Stranded California Sea Lion (Zalophus californianus) - a New Host-parasite Association. J. Wildlife Diseases, 41:593-598
Lucas, Z., Daoust, P=Y., Conboy, G., Brimacombe, M. 2003. Health status of harp seals (Phoca groenlandica) and hooded seals (Cystophora cristata) on Sable Island, Nova Scotia, Canada, concurrent with their expanding range. Journal of Wildlife Diseases 39: 16-28.
Oderka, D.K. 1989. Prevalence and pathology of nematode infections in the lungs of ringed seals (Phoca hispida) of the western arctic of Canada. Journal of Wildlife Diseases 25: 218-224.
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