Nematode Parasitism of Oysters


Category 4 (Negligible Regulatory Significance in Canada)

Common, generally accepted names of the organism or disease agent

Nematode parasitism of oysters, Larval nematode infection.

Scientific name or taxonomic affiliation

a) Echinocephalus crassostreai (superfamily Spiruroidea, family Gnathostomidae).
b) Unidentified nematode.

Geographic distribution

a) Coast of Hong Kong and adjacent coast of The People's Republic of China.
b) Louisiana coast of U.S.A.

Host species

a) Crassostrea gigas. Other species of Echinocephalus have been reported from abalone and sea urchins.
b) Crassostrea virginica.

Impact on the host

The second- and third-stage larvae of E. crassostreai occurs primarily encysted in the gonad of C. gigas with minimal associated pathology. However, this nematode may cause gastric or other types of granulomatous lesions in humans if accidentally ingested.

Diagnostic techniques

Gross Observations: Larval nematodes (18 to 21 mm long) with a head-bulb holding 6 to 8 rows of hooks with 30-50 hooks per row.

Methods of control

No known methods of prevention or control. However, elasmobranch fish infected with the adult stage of this parasite must occur in the vicinity of the oysters in order to initiate the infection in oysters.


Cheng, T.C. 1978. Larval nematodes parasitic in shellfish. Marine Fisheries Review 40: 39-42.

Gauthier, J.D. and T.M. Soniat. 1988. A parasitological survey of oysters (Crassostrea virginica) along the Louisiana coast. Journal of Shellfish Research 7: 204-205. (Abstract).

Citation Information

Bower, S.M. (2001): Synopsis of Infectious Diseases and Parasites of Commercially Exploited Shellfish: Nematode Parasitism of Oysters.

Date last revised: January 2001
Comments to Susan Bower

Date modified: