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BP virus disease, Nuclear polyhedrosis disease, Baculovirus disease, PIB ("polyhedral inclusion body") virus disease.
Scientific name or taxonomic affiliation
Baculovirus penaei Couch; a typeA occluded baculovirus that has been given the taxonomic designation of PvSNPV (the acronym represents: Pv = P. vannamei, the first species in which the agent was described; SNPV = singly enveloped nuclear polyhedrosis virus group). Several strains with different morphological characteristics, especially virion size, are likely to exist in different geographic regions.
Widespread in cultured and wild penaeids in the Americas ranging from the northern Gulf of Mexico south through the Caribbean and reaching at least as far south as central Brazil. On the Pacific coast BP ranges from Peru to Mexico and has been observed in wild penaeids from Hawaii. Probably enzootic through most of this range.
Penaeus aztecus, Penaeus vannamei, Penaeus duorarum, Trachypeanaeus similis, Penaeus setiferus, Penaeus stylirostris, Penaeus schmitti, Penaeus penicillatus, Penaeus brasiliensis, Penaeus paulensis, Penaeus subtilis, Penaeus marginatus, and possibly Penaeus californiensis.
Impact on the host
Infectious by horizontal transmission to all life stages but patent infections may not develop in shrimp older than the ninth molt postlarvae (PL-9) unless the animals were held under stressful conditions such as inadequate nutrition. Epizootics may be chronic to acute with high cumulative mortality but presence of virus does not always result in disease. Feeding and growth rates may be temporarily reduced; gill and surface fouling may be increased. Co-occurence of a reo-like virus has been reported in some BP-infected cultured P. vannamei larvae during experimental investigations on BP.
Squash Preparations: Single or multiple polyhedral occlusion (initally called inclusion) bodies (PIBs) in epithelial cell nuclei of hepatopancreas, anterior midgut or fresh faeces using phase or bright field microscopy. PIBs are tetrahedral or pyramidal and range in size from 0.1-20 µm from pyramidal base to peak with a modal, vertical length of 8-10 µm and number from 1-6 per nucelus in natural infections and up to 100 per nucleus in experimentally infected larvae. PIBs in squashes fluoresce under ultraviolet light following staining with 0.001% aqueous phloxine (Thurman et al. 1990) providing a rapid and specific diagnosis.
Histology: Necrosis and loss of hepatopancreatic and mid-gut epithelial cells. Single, or more often multiple, PIBs in the hypertrophied nucleus and chromatin diminution and margination in infected hepatopancreatic epithelial cells in advanced infections. PIBs stain bright red with methyl green-pyronin stain, eosinophilic with haematoxylin and eosin stain, and stain intensely with Gram's stain and toluidine blue. Brown & Brenn histologic Gram stain (Luna 1968), although not specific for baculovirus occlusion bodies, tends to stain occlusions more intensely (either red or purple, depending on section thickness, time of decolourization etc.) than the surrounding tissue, aiding in demonstrating their presence in low-grade infections. Another diagnostic tool for the identification of baculovirus occlusions involves epifluoresence light microscopy of histological sections stained with 0.005% phloxine as a component of the eosin part of normal haematoxylin and eosin staining (Thurman et al. 1990).
Electron Microscopy: Rod-shaped enveloped nucleocpasid virons (about 337 × 79 nm in P. vannamei from Ecuador, 330 × 75 from P. aztecus and P. duorarum from Florida and 286 × 56 nm in P. marginatus from Oahu, Hawaii) found free and occluded within proteinogenous crystalline matrix of the occlusion body (PIB). PIBs only occur during the advanced stages of infection. Virons are present in earlier stages of infection in conjunction with nuclear enlargement, aberrant stromatic patterns of the nucleoplasm, degenerate or absent nucleoli, and nuclear membrane proliferation into labyrinths.
DNA Probes: Genomic probes using dot blot assays and in situ hybridization may provide a useful diagnostic tool (Lightner et al. 1992, Bruce et al. 1993).
Bioassay: Third substage protozoea (Pz3) of P. vannamei are fed digestive glands and possibly other body parts of crustacea suspected to be infected. The Pz3's will exhibit patent infections with hypertrophic nuclei, PIBs, free virons and occluded virons within five or six days if the infective virons were present in the test material. Crowding and other culture stressors may enhance suspect BP infections in shrimp held in laboratory recirculating tanks. Samples of faeces from these shrimp should be examined at regular intervals for PIBs.
Methods of Control
No known treatment.
HEALTH MANAGEMENT & DISEASE CONTROL INDEX
Hepatopancreatic parvo-like virus (HPV) . Reo-like virus (REO) . 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) . You are here
Vibriosis . Epicommensal fouling disease (filementous bacteria) . Necrotizing Hepatopancreatitis (NHP) . Black spot disease (BSD) . Mycobacteriosis
Larval mycosis . Fusariosis
Haplosporidia . Gregarines . Cotton Disease
Black Gill Disease (BGD) Dissolved Oxygen Crisis Nitrogen Gas Bubble Disease