Mycobacteriosis of Penaeid Shrimp

Category

Category 3 (Host Not in Canada)

Common, generally accepted names of the organism or disease agent

Mycobacteriosis, Shrimp tuberculosis.

Scientific name or taxonomic affiliation

Mycobacterium marinum, Mycobacterium fortuitum, and Mycobacterium sp.

Geographic distribution

Ubiquitous.

Host species

Potentially infectious to all penaeids.

Impact on the host

Infected shrimp produce unsightly melanized nodules or lesions on the shell or in the muscle that pose more of a problem to marketing than to losses due to mortalities. Also, these bacteria have been reported to cause accidental infections in the hands of shrimp farm or packing plant workers that resulted in nodular skin lesions that were difficult to treat.

Diagnostic techniques

Gross Observations: Multifocal melanized areas in the tissues (muscle, ovary, heart, gills, etc.) or large raised irregular melanized lesions in or on the cuticle.

Smears: Demonstration of Gram positive, acid-fast (by Zeihl-Neelsen stain or related methods), rod-shaped bacteria in impression smears from melanized lesions.

Histology: The presence of acid-fast, Gram positive, rod-shaped bacteria in the melanized lesions is required to make a diagnosis to the genus Mycobacterium. The lesions consist of multifocal, usually heavily melanized, haemocytic nodules or larger granulomatous lesions. With haematoxylin and eosin stain, palely basophilic rod-shaped bacteria may be evident in, or associated with the haemocytic nodules.

Culture: Isolation of an acid-fast bacterium on special media for Mycobacterium spp.

Methods of control

No known methods of prevention or control.

References

Lightner, D.V. (ed.). 1996. A Handbook of Shrimp Pathology and Diagnostic Procedures for Disease of Cultured Penaeid Shrimp. World Aquaculture Society, Baton Rouge.

Citation Information

Bower, S.M. (1996): Synopsis of Infectious Diseases and Parasites of Commercially Exploited Shellfish: Mycobacteriosis of Penaeid Shrimp.

Date last revised: September 1996
Comments to Susan Bower

Date modified: