Language selection


Reo­like Virus (REO) Disease of Penaeid Shrimp


Category 3 (Host Not in Canada)

Common, generally accepted names of the organism or disease agent

Reo­like virus (REO or RLV) disease.

Scientific name or taxonomic affiliation

Reo is an icosahedral double strand RNA reo-like virus belonging to the family Reoviridae. At least two types of reo-like viruses (REO-III and REO-IV) are known in penaeid shrimp.

Geographic distribution

  1. REO-III: Japan (cultured P. japonicus); Hawaii (P. japonicus stocks imported from Japan); France in tank-reared P. japonicus; Malaysia (pond-cultured Penaeus monodon in conjunction with MBV, a ricksettsia and Gram negative bacteria); Mississippi, USA and Equador (in cultured P. vannamei).
  2. REO-IV: Yellow Sea region of northeast Asia (in cultured and wild P. chinensis)

Host species

  1. Penaeus japonicus, Penaeus monodon and Penaeus vannamei.
  2. Penaeus chinensis.

Impact on the host

REO infections usually associated with multiple infections by other pathogens (viral, fungal and/or bacterial). Possible link between infection by REO and "gut and nerve syndrome" (GNS), an idiopathic condition found in chronically ill populations of P. japonicus cultured in Hawaii and France. Status as a pathogen of penaeid shrimp remains to be established but REO may be a predisposing factor for other infections (e.g., with Fusarium).

Diagnostic techniques

Gross Observations: May be masked by gross signs of infection by other agents include: reddish discolouration of telson, uropods and hepatopancreas, poor feeding and growth, anorexia, lethargy, reduced preening, increased surface fouling, secondary infections (especially with Fusarium) were common.

Histology: Hepatopancreatic atrophy and necrosis. Occasionally with pale basophilic to somewhat magenta to eosinophilic cytoplasmic inclusions in hepatopancreatocytes. Due to similarity with other inclusions such as phagolysosomes or inclusions due to other viruses, definitive diagnosed requires transmission electron microscopy.

Electron Microscopy: Demonstrate Reo-like non-enveloped icosahedral virons about 40-70 nm in diameter in cytoplasmic masses or membrane-bound cytoplasmic inclusion bodies in principally F- and R-type cells of the hepatopancreatic tubule epithelium. In P. vannamei, reo-like virons also observed in the epithelial cells of the anterior midgut.

Methods of control

No known treatment.


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. 277.

Krol, R.M., W.E. Hawkins and R.M. Overstreet. 1990. Reo-like virus in white shrimp Penaeus vannamei (Crustacea: Decapoda): co-occurrence with Baculovirus penaei in experimental infections. Diseases of Aquatic Organisms 8: 45-49.

Lightner, D.V. 1988. Reo-like virus (Reo) disease 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. 33-37.

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. and R.M. Redman. 1992. Penaeid virus diseases of the shrimp culture industry of the Americas. In: A.W. Fast and L.J. Lester (eds.). Marine Shrimp Culture: Principles and Practices. Developments in Aquaculture and Fisheries Science 23. Elsevier, Amsterdam, p. 569-588.

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: 267-274.

Nash, M., G. Nash, I.G. Anderson and M. Shariff. 1988. A reo-like virus observed in the tiger prawn, Penaeus monodon Fabricius from Malaysia. Journal of Fish Diseases 11: 531-535.

Tsing, A. and J.R. Bonami. 1984. A new virus disease in the shrimp Penaeus japonicus. Abstract In: C.P. Vivarès, J.R. Bonami and E. Jaspers (eds.). Pathology in marine aquaculture (Pathologie en aquaculture marine). European Aquaculture Society, Special Publication 9. Bredene, Belguim, p. 295.

Citation Information

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

Date last revised: Fall 1996
Comments to Susan Bower

Date modified: