Baculovirus penaei (BP Virus Disease) of Penaeid Shrimp
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Category
Category 3 (Host Not in Canada)
Common, generally accepted names of the organism or disease agent
BP virus disease, Nuclear polyhedrosis disease, Baculovirus disease, PIB (“polyhedral inclusion body”) virus disease.
Scientific name or taxonomic affiliation
Baculovirus penaei Couch; a type-A 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.
Geographic distribution
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.
Host species
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.
Diagnostic techniques
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 x 79 nm in P. vannamei from Ecuador, 330 x 75 from P. aztecus and P. duorarum from Florida and 286 x 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. Implement the following management techniques to reduce or eliminate disease where the virus is endemic in the broodstock: use only nauplii spawned from females not passing PIBs in their faeces, or PIB negative on hepatopancreas biopsy; reduce vertical transmission by improved hygiene during spawning and hatching (vertical transmission occurs by faecal contamination of eggs); implement rigorous husbandry and sanitation procedures to eliminate cross-transmission between tank batches of larvae; and, disinfect equipment with an alkaline disinfectant.
References
Bonami, J.-R., L.D. Bruce, B.T. Poulos, J. Mari and D.V. Lightner. 1995. Partial characterization and cloning of the genome of PvSNPV (=BP-type virus) pathogenic for Penaeus vannamei. Diseases of Aquatic Organisms 23: 59-66.
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. 249-254.
Couch, J.A. 1981. Virus diseases of invertebrates other than insects. In: E.W. Davidson (ed.). Pathogenesis of Invertebrate Microbial Diseases. Allandeld Osmun Publishers, Totowa, NJ, p. 125-160.
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. BP (Baculovirus penaei) disease of penaeid shrimp. In: C.J. Sindermann and D.V. Lightner (eds.). Disease Diagnosis and Control in North American Aquaculture. Developments in Aquaculture and Fisheries Science 17. Elsevier, Amsterdam, p. 16-21.
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., B.T. Poulos, L. Bruce, R.M. Redman, J. Mari and J.R. Bonami. 1992. New developments in penaeid virology: application of biotechnology in research and disease diagnosis for shrimp viruses of concern in the Americas. In: W. Fulks and K.L. Main (eds.). Diseases of Cultured Penaeid Shrimp in Asia and the United States. The Oceanic Institute, Honolulu, p. 233-253.
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 World Mariculture Society 16: 267-274.
Luna, L.G. (ed.). 1968. Manual of Histologic Staining Methods of the Armed Forces Institute of Pathology. McGraw-Hill Book Company, New York.
Overstreet, R.M., K.C. Stuck, R.A. Krol and W.E. Hawkins. 1988. Experimental infections with Baculovirus penaei in the white shrimp Penaeus vannamei(Crustacea: Decapoda) as a bioassay. Journal of the World Aquaculture Society 19: 175-187.
Stuck, K.C. and R.M. Overstreet. 1994. Effect of Baculovirus penaei on growth and survival of experimentally infected post larvae of the Pacific white shrimp, Penaeus vannamei. Journal of Invertebrate Pathology 64: 18-25.
Thurman, R.B., T.A. Bell, D.V. Lightner and S. Hazanow. 1990. Unique physicochemical properties of the occluded penaeid shrimp baculoviruses and their use in diagnosis of infections. Journal of Aquatic Animal Health 2: 128-131.
Citation Information
Bower, S.M. (1996): Synopsis of Infectious Diseases and Parasites of Commercially Exploited Shellfish: Baculovirus penaei (BP Virus Disease) of Penaeid Shrimp
Date last revised: September 1996
Comments to Susan Bower
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