Rickettsial Infection of Penaeid Shrimp


Category 3 (Host Not in Canada)

Common, generally accepted names of the organism or disease agent

Rickettsial infection of penaeids.

Scientific name or taxonomic affiliation

Rickettsia­like organisms.

Geographic distribution

Wild caught Penaeus marginatus and experimentally in Penaeus stylirostris in Hawaii, cage reared Penaeus merguiensis in Singapore, and cultured Penaeus monodon in Malaysia and Indonesia.

Host species

Penaeus monodon, Penaeus merguiensis, Penaeus marginatus and experimental infection of Penaeus stylirostris.

Impact on the host

Heavily infected shrimp are lethargic, do not feed and congregate in the shallows along the edges of the shrimp ponds. In P. marginatus, P. merguiensis and P. stylirostris, the infection occurs in the hepatopacreas epithelium, and may result in atrophy and pale discolouration of this organ. In P. monodon, the infection is widespread in mesodermally and ectodermally derived tissues (i.e. the fixed phagocytes, antennal gland and Y organ cells, gills (where it causes brown discolouration), abdominal musculature (that acquire a diffuse opacity) and the hepatopancreas (which becomes mushy in texture)) but absent in endodermally derived tissues (i.e. the midgut, hepatopancreas and caeca), distinquishing this organism from the forms described above. Infections in P. monodon occurred concurrently with other biotic agents including Gram negative bacterial septicemia, monodon baculovirus (MBV) and Reo-like virus. Mortalities were often associated with infections in cultured shrimp.

Diagnostic techniques

Gross Observations: As above.

Histology: Rickettsia-like organisms (0.2-0.7 × 0.8-1.6 µm) filling cytoplasmic vacuoles (5-50 µm and staining basophilic with haematoxylin and eosin stain, Gram negative, and Feulgen positive) within specific target cells of host species as indicated above.

Methods of control

Rickettsial infections have been effectively treated with various antibacterial drugs in feed. However, every effort should be made to prevent the introduction of these pathogens by screening potential carriers and destroying infected stocks followed by disinfection of contaminated area.


Brock, J.A. 1988. Rickettsial infection of penaeid shrimp. 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. 38-41.

Brock, J.A. and D.V. Lightner. 1990. Diseases of Crustacea. Diseases caused by microorganisms. In: O. Kinne (ed.). Diseases of Marine Animals. Volume III: Introduction, Cephalopoda, Annelida, Crustacea, Chaetognatha, Echinodermata, Urochordata. Biologische Anstalt Helgoland, Hamburg, p. 292-295.

Brock, J.A., L.K. Nakagawa, T. Hayashida, S. Teruya and H. Van Campen. 1985. Hepatopancreatic rickettsial infection of shrimp, Penaeus marginatus Randall, from Hawaii. Journal of Fish Diseases 9: 73­77.

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

Lightner, D.V., T.A. Bell, R.M. Redman, L.L. Mohney, J.M. Natividad, A. Rukyani and A. Poernomo. 1992. A review of some major diseases of economic significance in penaeid prawns/shrimp of the Americas and Indopacific. In: M. Shariff, R.P. Subasinghe and J.R. Arthur (eds.). Diseases in Asian Aquaculture. I. Fish Health Section, Asian Fisheries Society. Manila, Philippines, p. 57-80.

Lightner, D.V., R.M. Redman, R.R. Williams, L.L. Mohney, J.M.P. Clerx, T.A. Bell and J.A. Brock. 1985. Recent advances in penaeid virus disease investigations. Journal of the World Mariculture Society 16: 267­276.

Citation Information

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

Date last revised: September 1996
Comments to Susan Bower

Date modified: