White spot syndrome

White spot syndrome virus is the lone virus (types and species) of the genus Whispovirus ( whi te spo t), qui is the only genus in the family Nimaviridae . It is responsible for the treatment of white spot in a wide range of crustacean hosts. [1] White spot syndrome (WSS) is a viral infection of penaeid shrimp . The disease is highly lethal and contagious, killing shrimps quickly. Outbreaks of this disease have spread to many people worldwide .

The disease is caused by a family of related viruses subservient to the Whitespot Syndrome Baculovirus complex (WSSV) [2] and the disease caused by white spot syndrome (WSS). [3]

History

The first reported epidemic of this virus is from Taiwan in 1992; [4] However , reports of losses from China in 1993, [5] where it was possible to collapse the farming industry. Reviews This was Followed by outbreaks in Japan and Korea in the Sami year, Thailand , India and Malaysia in 1994 and by 1996 It Had Severely affected East Asia and South Asia . In late 1995, it was reported in the United States, 1998 in Central and South America , 1999 in Mexico ‘in 2000 in the Philippines, and in 2011 in Saudi Arabia . The virus was detected in Queensland , Australia in November 2016. [6] Australia was believed to be the last shrimp-growing region of the virus.

Virology

White spot syndrome is a species of virus in the genus Whispovirus , in the family Nimaviridae . It is the only species in this family, and so are the species species. [1] [7]

Taxonomy

White spot syndrome virus is a dsDNA virus, which places it in Group I of the Baltimore classification system.

Group: dsDNA

Order: Unassigned[show]

[7]

Virion Structure

WSSV is a rod-shaped, double-stranded , DNA virus , and the size of the enveloped viral particles were reported to be 240-380 nm long and 70-159 nm in diameter and nucleocapsid core is 120-205 nm long and 95 -165 nm in diameter. The virus has an outer lipid bilayer membrane envelope, sometimes with a tail like appendage at one end of the virion. The nucleocapsid consists of 15 consecutive vertical strands, consisting of 14 globular capsomers, each of which is 8 nm in diameter. [8]

genus Structure Symmetry capsid Genomic arrangement Genomic segmentation
Whispovirus ovoid enveloped Circular one-party

Genome

The complete DNA sequence of WSSV genome has been assembled into a circular sequence of 292,967 bp . [9] It encodes 531 putative open reading frames.

One of the proteins – WSSV449 – has some similarity to host protein. [10]

Life cycle

Viral replication is nuclear. DNA-templated transcription is the method of transcription. The virus infects an unusually wide host range of crustaceans. [1] Transmission of the virus is mainly through oral ingestion and water-bound roads in farms (horizontal transmission) and vertical transmission (from infected mother prawns) in the case of shrimp hatcheries. The virus is present in the wild stocks of shrimp, especially in the coastal areas of the world, but is not yet observed.

genus Host details Tissue tropism Entry details Release details Replication site Assembly site Transmission
Whispovirus Crustaceans ectoderm; mesoderm Unknown Unknown Nuclear Nuclear Contact

Clinical

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The virus has a wide host range. While shrimp can survive with the virus for extended periods of time, these factors can cause the outbreak of WSS. The disease is highly virulent and leads to mortality in the case of cultured penaeid shrimps. Most of the cultured penaeid shrimps ( Penaeus monodon , Marsupenaeus japonicus , Litopenaeus vannamei , and Fenneropenaeus indicus ) are natural hosts of the virus. Several non-penaeid shrimps were also found to be severely infected during experimental challenges. Many crustaceans like crabs ( Scylla spp. , Portunus spp. ),spiny lobsters ( Panulirus spp. ), crayfish ( Astacus spp. , Cherax spp. ) and freshwater shrimp ( Macrobrachium spp. ) are Reported to be infected with varying severities DEPENDING on the life course of the host and the presence of external stressors ( temperature , salinity , bacterial diseases, pollutants).

Clinical signs of WSS include lethargy, loose cuticle and often reddish discolouration, and the presence of white spots of 0.5 to 2.0 mm in diameter on the inside surface of the carapace , appendages and cuticle over the abdominal segments.

Pathology

In the host, WSSV infects a wide variety of cells from ectodermal and mesodermal origin. Histologic changes are seen in the epithelial gill , antennal glans , haematopoeitic tissue , nervous tissue , connective tissue and intestinal epithelial tissue . Infected cells have prominent intranuclear occlusions that initially stain eosinophilic , but become basophilic with age; hypertrophied nuclei with chromatin margination; and cytoplasmic clearing. [11] Pathogenesis provides widespread tissue necrosis and disintegration.

White spots on the shell of infected shrimp under scanning electron microscope appear as large, dome-shaped spots on the carapace measuring 0.3 to 3 mm in diameter. Smaller white spots of 0.02 to 0.1 mm appear on the surface. Chemical composition of the spots is similar to the carapace, calcium forming 80-90% of the total material and it is suggested to have derived from abnormalities of cuticular epidermis. [12]

Abstract: [13] glucose consumption and plasma lactate concentration increase, glucose 6 phosphate dehydrogenase activity increases and triglyceride concentration decreases. The voltage dependent anion channel of the mitochondrion is also up regulated.

Diagnosis

Infection with WSSV differs from other described penaeid infections Yellowhead virus (YHV) and Infectious Hypodermal and Hematopoietic Necrosis virus (IHHNV) in the described histological findings as YHV has reduced tissue specificity, infecting only the intestinal epithelial tissues and IHHNV causes intranuclear occlusions that stain eosinophillic but do not change over the course of the infection. [11]

Rapid and specific diagnosis of the virus can be accomplished using nested [11] or quantitative PCR . [14]

Treatment

There are no available treatments for WSS.

Prevention

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A large number of disinfectants are widely used in shrimp farms and hatcheries to prevent an outbreak. The importance of environmental protection and the prevention of environmental contamination. Site selection may be one of the most crucial in preventing White Spot Disease. A study showed that shrimps were relatively high in temperature and at temperatures higher than 29 ° C had increased resistance to WSSV. [15]

References

  1. ^ Jump up to:c “Viral Zone” . ExPASy . Retrieved 15 June 2015 .
  2. Jump up^ “Non-Native Species Summaries: Whitespot Syndrome Baculovirus Complex (WSBV)  . Gulf States Marine Fisheries Commission. 2003 . Retrieved June 30, 2005 .
  3. Jump up^ Lightner, DV (1996). A handbook of shrimp pathology and diagnostic procedures for diseases of cultured penaeid shrimp . World Aquaculture Society, Baton Rouge, Louisiana, USA.
  4. Jump up^ Chen, SN (1995). “Current status of shrimp aquaculture in Taiwan.” In CL Browdy; JS Hopkins. Swimming through troubled water . Proceedings of the special session on shrimp farming. Aquaculture ’95. World Aquaculture Society, Baton Rouge, Louisiana, USA. pp. 29-34.
  5. Jump up^ Huang, J .; XL Song; J. Yu & CH Yang (1995). “Baculoviral hypodermal and hematopoietic necrosis: a study on the pathogen and pathology of the explosive epidemic disease of shrimp”. Marine Fisheries Research . 16 : 1-10.
  6. Jump up^ “White Spot Detected on Queensland Prawn Farm” . The Fish Site . December 2, 2016 . Retrieved 2016-12-08 .
  7. ^ Jump up to:b ICTV. “Taxonomy Virus: 2014 Release” . Retrieved 15 June 2015 .
  8. Jump up^ Nadala, ECB Jr .; LM Tapay & PC Loh (1998). “Characterization of a non-occluded baculovirus-like pathogenic agent to penaeid shrimp”. Diseases of Aquatic Organisms . 33 (3): 221-229. doi : 10.3354 / dao033221 . PMID  9745719 .
  9. Jump up^ Van Hulten, MCW; J. Witteveldt; S. Peters; N. Kloosterboer; R. Tarchini; F. Proud; H. Sandbrink; RK Lankhorst & JM Vlak (2001). “The white spot syndrome virus DNA genome sequence”. Virology . 286 (1): 7-22. doi :10.1006 / viro.2001.1002 . PMID  11448154 .
  10. Jump up^ Wang, PH; Gu, ZH; Wan, DH; Zhang, MY; Weng, SP; Yu, XQ; He, JG (2011). “The shrimp NF-κB pathway is activated by white spot syndrome virus (WSSV) 449 to facilitate the expression of WSSV069 (ie1), WSSV303 and WSSV371” . PLoS ONE . 6 (9): e24773. doi : 10.1371 / journal.pone.0024773 . PMC  3171479  . PMID  21931849 .
  11. ^ Jump up to:c Wongteerasupaya, C .; I Vickers; S. Sriurairatana; GL Nash; A. Akarajamorn; V. Boonseang; S. Panyin; A. Tassanakajon; B. Withyachumnarnkul & TW Flegel (1995). “A non-occluded, systemic baculovirus that occurs in cells of ectodermal and mesodermal origin and causes high mortality in the black tiger prawn Penaeus monodon “. Diseases of Aquatic Organisms . 21 : 69-77. doi : 10.3354 / dao021069.
  12. Jump up^ Wang, CS; KF Tang; GH Kou & SN Chen (1997). “Light and electron microscopic evidence of white spot disease in the giant tiger shrimp,Penaeus monodon (Fabricius), and the kuruma shrimp, Penaeus japonicus (Bate), cultured in Taiwan”. Journal of fish Diseases . 20 (5): 323-331. doi : 10.1046 / j.1365-2761.1997.00301.x .
  13. Jump up^ IT Chen, Aoki T, Huang YT, Hirono I, TC Chen, Huang JY, Chang GD, CF Lo, Wang KC (2011) White spot syndrome virus metabolic induces reshaping the Warburg effect in shrimp hemocytes in the early stage of infection. J Virol
  14. Jump up^ Dhar, AK; MM Roux & KR Klimpel (2001). “Detection and Quantification of Infectious Hypodermal and Hematopoietic Necrosis Virus and White Spot Virus in Shrimp Using Real-Time Quantitative PCR and SYBR Green Chemistry” . Journal of Clinical Microbiology . 39 (8): 2835-2845. doi :10.1128 / JCM.39.8.2835-2845.2001 . PMC  88247  . PMID  11474000 .
  15. Jump up^ Kakoolaki, S .; Sharifpour, I .; Afsharnasab, M .; Sepahdari, A .; Mehrabi, MR; Ghaednia, B .; Nezamabadi, H. (2014). “Effects of temperature on hematological and histopathological changes and survival rate of juvenile Fenneropenaeus vannamei experimentally challenged to White Spot Virus” . Iranian Journal of Fisheries Sciences . 13 (1): 91-102.

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