Chitinolytic Bacterial Shell Disease of Crabs


Category 4 (Negligible Regulatory Significance in Canada)

Common, generally accepted names of the organism or disease agent

Chitinolytic bacterial disease, Shell disease, Box burnt disease, Bacterial shell disease.

Scientific name or taxonomic affiliation

Chitinolytic or chitinoclastic bacteria (Gram negative) including Vibrio spp., Pseudomonas spp. and Aeromonas spp.

Geographic distribution


Host species

Cancer spp., Callinectes sapidus, other crabs; lobsters, shrimps and crayfish.

Impact on the host

The exoskeleton becomes pitted, eroded, and melanized at the site of infection, frequently occurring on chelipeds and the edge of the carapace overlying the gills. Infection found to coincide with low serum antibacterial activity. Not usually lethal but secondary infections may cause internal necrosis of tissues and death.

Diagnostic techniques

Gross Observations: Erosion of chitin demarked by dark brown to black pigmentation.

Culture: Culture lesion on marine agar. Test isolated bacteria in saline solution with thin chitin strips to demonstrate chitinolysis.

Methods of control

No known methods of prevention or control. Disease is a common problem of crustaceans in polluted environments and is particularly apparent when crabs have been injured or held in prolongued captivity.


Fisher, W.S. 1988. Shell disease of lobsters. In: C.J. Sindermann and D.V. Lightner (eds.). Disease Diagnosis and Control in North American Aquaculture. Developments in Aquaculture and Fisheries Science 17. Elsevier, Amsterdam, p. 236-239.

Messick, G.A. and C.J. Sindermann. 1992. Synopsis of principal diseases of the blue crab, Callinectes sapidus. NOAA Technical Memorandum NMFS-F/NEC-88. 24 p.

Noga, E.J., D.P. Engel, T.W. Arroll, S. McKenna and M. Davidian. 1994. Low serum antibacterial activity coincides with increased prevalence of shell disease in blue crabs Callinectes sapidus. Diseases of Aquatic Organisms 19: 121-128.

Rosen, B. 1970. Shell disease of aquatic crustacea. In: S.F. Sniesko (ed.). A Symposium on Diseases of Fishes and Shellfishes. American Fisheries Society Special Publication 5: 409-415.

Citation Information

Bower, S.M. (1996): Synopsis of Infectious Diseases and Parasites of Commercially Exploited Shellfish: Chitinolytic Bacterial Shell Disease of Crabs.

Date last revised: September 1996
Comments to Susan Bower

Date modified: