Otostrongylus circumlitus

Otostrongylus circumlitus	Contents	Rev 05/08/2026
Lungworm of seals	Classification	Biology and Ecology
	Morphology and Anatomy	Life Cycle
Return to Otostrongylus Menu		Ecosystem Functions and Services
	Distribution	Management
Return to Crenosomatidae Menu	Feeding	References
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Otostrongylus circumlitus (Railliet, 1899) de Bruyn, 1933

Type species of the genus

Synonyms:

Morphology and Anatomy:

Elson-Riggins et al (2001) determined that, based on molecular and morphometric charactersitics, there was no evidence that populations from Pacific harbor seals and northern elephant seals were different species.
Vulva at 48-57% of body length

Reported median body size for this species (Length mm; width micrometers; weight micrograms) - Click:

Light micrograph (Nomarski optics) of male bursas of Otostrongylus circumlitus from Pacific harbor seal (A) and northern elephant seal (B). Bar 5 100 um
Photographs from Elson-Riggins et al., 2001

Distribution:

Otostrongylus circumlitus, a circumpolar metastrongyloid nematode, is primarily a parasite of seals (Onderka, 1989; Kelly et al., 2005).

Otostrongylus 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).

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Biology and Ecology:

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).

between January 1992 and December 1995, Gulland et al. (1997) reported 37% of northern elephant seal weanling deaths and 12% of Pacific harbor seal deaths at The Marine Mammal Center (TMMC, a rehabilitation center), in Sausalito, California were associated with O. circumlitus.

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Life Cycle:

Life cycle is indirect.

Intermediate host range uncertain but probably mainly fish. 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).

Ecophysiological Parameters:

For Ecophysiological Parameters for this species, click	If species level data are not available, click for genus level parameters

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Ecosystem Functions and Services:

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Management:

Anthelminthics

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References:

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.

Elson-Riggins, J.G., Al-Banna, L., Platzar, E.G., Kaloshian, I. 2001. Characterization of Otostrongylus circumlitus from Pacific Harbor and Northern Elephant Seals. J. Parasitol., 87:73-78.

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.