Mesanophrys spp. (Ciliate Disease) of Crabs


Category 2 (In Canada and of Regional Concern)

Common, generally accepted names of the organism or disease agent

Ciliate disease of crabs.

Scientific name or taxonomic affiliation

Holotrich, scuticociliate parasite Mesanophrys (=Paranophrys, =Anophrys) sp., Mesanophrys maggii in Cancer maenas, Mesanophrys chesapeakensis in Callinectes sapidus, Mesanophrys carcini in Cancer pagurus and Mesanophrys pugettensis in Cancer magister, Cancer productus, Pugettia producta.

Geographic distribution

Broad geographic range including Europe and the Pacific coast of North America.

Host species

Carcinus maenas, Cancer pagurus, Cancer magister, Callinectes sapidus, Cancer productus, Cancer irroratus, Pugettia producta, Chionoecetes bairdi (dual infections with Hematodinium sp.) and Lithodes aequispina and Paralithodes platypus held in captivity for at least 2 months (related species infect lobsters and cultured Penaeid shrimp).

Impact on the host

Postulated to gain entry at a site of injury to the exoskeleton and to spread throughout the body via the circulatory system. Ciliate multiplies to high densities. They consume haemocytes and muscle tissue eventually resulting in the death of the crab due to systemic tissue destruction. Infection was associated with mortalities among a large number of recently molted C. magister in Samish Bay, Puget Sound, WA in mid-spring of 1990-1992.

Diagnostic techniques

Gross Observations: Infected individuals lethargic, unable to right themselves after being overturned. Hearts of heavily infected individuals may have white areas of tissue necrosis.

Wet mount: Ciliates of typical elongate form in haemolymph, often in large numbers; haemocytes absent in advanced infection.

Histology: Ciliates present in haemal sinuses of all tissues, especially heart and gill, with associated tissue damage.

Methods of control

Because most reports of infection are in injured crabs being held in enclosures, reducing crab densities and mechanical damage to crabs during holding may be beneficial.


Armetta, T.M. 1990. Hemolymph changes in Dungeness crab caused by infection with the ciliated protozoan parasite Mesanophrys sp. Masters of Science Thesis, University of Washington. 58 p.

Armstrong, D.A., E.M. Burreson and A.K. Sparks. 1981. A ciliate infection (Paranophrys sp.) in laboratory-held Dungeness crabs, Cancer magister. Journal of Invertebrate Pathology 37: 201-209.

Bang, F.B., J. Audouin and M. Leglise. 1972. Ciliate infection of the blood of the edible crab, Cancer pagurus, in holding tanks in Brittany, France. Journal of Invertebrate Pathology 20: 226-227.

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Morado, J.F. (1993): The morphology, morphogenesis, culture and pathogenesis of a marine facultative parasitic ciliate, Mesanophrys sp., of the Dungeness crab, Cancer magister, and its occurrence in wild crustacean populations. Ph.D. Thesis, University of Washington, Seattle. 248 p.

Morado, J.F. and E.B. Small. 1994. Morphology and stomatogenesis of Mesanophrys pugettensis n. sp. (Scuticociliatida: Orchitophryidae), a facultative parasitic ciliate of the Dungeness crab, Cancer magister (Crustacea: Decapoda). Transactions of the American Microscopical Society 113: 343-364.

Morado, J.F. and E.B. Small. 1995. Ciliate parasites and related diseases of Crustacea: a review. Review in Fisheries Science 3: 275-354.

Sindermann, C.J. 1988. Ciliate (Paranophrys) disease of Dungeness crabs. In: C.J. Sindermann and D.V. Lightner (eds.). Disease Diagnosis and Control in North American Marine Aquaculture. Developments in Aquaculture and Fisheries Science 17. Elsevier, Amsterdam, p. 220-221.

Sparks, A.K., J. Hibbits and J.C. Fegley. 1982. Observations on the histopathology of a systemic ciliate (Paranophrys sp.?) disease in the Dungeness crab, Cancer magister. Journal of Invertebrate Pathology 39: 219-228.

Citation Information

Bower, S.M. (1996): Synopsis of Infectious Diseases and Parasites of Commercially Exploited Shellfish: Mesanophrys spp. (Ciliate Disease) of Crabs.

Date last revised: September 1996
Comments to Susan Bower

Date modified: