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Post larval fitness parameters

Post Larva Acclimitation


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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
a) 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 Ecuador (in cultured P. vannamei).
b) REO-IV: Yellow Sea region of northeast Asia (in cultured and wild P. chinensis)

Host species
a) Penaeus japonicus, Penaeus monodon and Penaeus vannamei.
b) 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.




Variables to be used in health evaluation

Health evaluation tests
Wet Mount Procedure . PL visual examination . Stress test for post larva . Gill examination . Mid-gut Examination . Stomach Contents Analysis

Shrimp Diseases
Hepatopancreatic parvo-like virus (HPV) . You are here . Lymphoid organ vacuolization virus (LOVV) . Taura Syndrome Virus (TSV) . Rhabdovirus of Penaeid Shrimp (RPS) . White Spot Syndrome Virus (WSSV) . Infectious hypodermal and hematopoietic virus (IHHNV) . Baculovirus penaei (BP)
Bacterial Diseases
Vibriosis . Epicommensal fouling disease (filementous bacteria) . Necrotizing Hepatopancreatitis (NHP) . Black spot disease (BSD) . Mycobacteriosis
Fungal Diseases
Larval mycosis . Fusariosis
Haplosporidia . Gregarines . Cotton Disease
Black Gill Disease (BGD) Dissolved Oxygen Crisis Nitrogen Gas Bubble Disease

Disease control
Decreasing density, partial or early harvests . Drugs, chemicals and treatments . Sanitation