Nematode Parasitism of Abalone


Category 3 (Host Not in Canada)

Common, generally accepted names of the organism or disease agent

Nematode parasitism of the abalone foot, Larval nematode infection.

Scientific name or taxonomic affiliation

Echinocephalus pseudouncinatus (superfamily Spiruroidea, family Gnathostomidae).

Geographic distribution

Southern California, USA and Gulf of California, Mexico.

Host species

Haliotis corrugata and Haliotis fulgens, also reported from several species of sea urchins.

Impact on the host

The blisters associated with the cysts surrounding the larval nematode and burrowing of the nematode larvae through the abalone foot prior to encystment, apparently weakens the muscle and decreases the efficacy of this structure as a hold-fast organ making infected abalone easy to remove from the rock substrate. Abalone and sea urchins serve as intermediate host for this nematode which is thought to develop to adults in elasmobranch fish (the definitive hosts), specifically, the horned shark (Heterodontus francisci) and the bat stingray (Myliobatis californicus) (Millemann 1963). Ingestion of living worms may cause larval migrans in humans, a situation where the larval nematode does not develop into an adult but penetrates through the gut wall and wanders aimlessly in the body before being overcome by the person's internal defense mechanisms.

Diagnostic techniques

Gross Observations:

Blister-like cysts in the ventral portion of the foot containing 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 abalone in order to initiate the infection in abalone.


Bower, S.M. 2000. Infectious diseases of abalone (Haliotis spp.) and risks associated with transplantation. In: Campbell, A. (Editor), Workshop on Rebuilding Abalone Stocks in British Columbia. Canadian Special Publication of Fisheries and Aquatic Sciences 130: In press.

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

Kuris, A.M., R.J. Schmitt and R. Hedrick. 1994. Abalone wasting disease: role of coccidian parasites and environmental factors. In: California Sea Grant Biennial Report of Completed Projects 1990-92. California Sea Grant College, La Jolla, CA, pp. 120-123.

Millemann, R.E. 1951. Echinocephalus pseudouncinatus n.sp., a nematode parasite of the abalone. The Journal of Parasitology 37: 435-439.

Millemann, R. E. 1963. Studies on the taxonomy and life history of Echinocephalid worms (Nematoda: Spiruroidea) with a complete description of Echinocephalus pseudouncinatus Millemann, 1951. Journal of Parasitology 49: 754-764.

Pearse, J.S. and R.W. Timm. 1971. Juvenile nematodes (Echinocephalus pseudouncinatus) in the gonad of sea urchins (Centrostephanus coronatus) and their effect on host gametogenesis. The Biological Bulletin (Woods Hole, Mass.) 104: 95-103.

Citation Information

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

Date last revised: January 2001
Comments to Susan Bower

Date modified: