White spot syndrome virus (WSSV)White spot syndrome (WSS) is a viral infection of shrimp. Outbreaks of this disease have wiped out the entire populations of many shrimp farms within a few days, in places throughout the world. aquaculture shrimp farming diseases.

1. Presentation By..,
Mr. R. Hariharasuthan B.Voc,
M.Sc.,Coastal Aquaculutre 1st
Yr,

2. White spot syndrome (WSS) is a viral infection of shrimp. Outbreaks of this
disease have wiped out the entire populations of many shrimp farms within a few
days, in places throughout the world.
White spot syndrome virus (WSSV) is the lone virus of the
genus Whispovirus (white spot), which is the only genus in the
family Nimaviridae. It is responsible for causing white spot syndrome in a wide
range of crustacean hosts.
The disease is caused by a family of related viruses subsumed as the white spot
syndrome baculovirus complex and the disease caused by them as white spot
syndrome
INTRODUCTION

3. HISTORY OF WSSV (TIMELINE)

4. DIFFERENT NAMES OF WSSV (TIMELINE)
1ST Decade – Rod shaped nuclear virus
(1994)
Hypodermal and haematopoietic necrosis
baculovirus(1995)
White spot baculovirus
Later, viruses were recogonized as one and the same virus
and assigned by INTERNATIONAL COMMITTEE on VIRUS
TAXONOMY to its own New Genus
Genus : Whispovirus , in the family
Nimaviridae (Mayo,2002)

5. MORPHOLOGY OF WSSV
• WSSV is a dsDNA, which is rod-shaped, non-
occluded and enveloped with tail-like appendages.
• Intact enveloped virions are 80-120 nm wide and
250-380 nm long
• The viral envelope is 6 - 7 nm thick and is
constructed by a lipid bilayer membrane.
• The space between the envelope and the
nucleocapsid ranges from 2 to 7.5 nm. The
nucleocapsid is a cylinder of 65 x 200 nm. The
external wall of the nucleocapsid is 6 nm thick.
• More than 40 structural proteins have been
identified so far. Of these, 30 are located in the viral
envelope, 5 in the tegument and 7 in the
nucleocapsid.

6. • White spot syndrome virus is highly infective for marinepenaeid shrimp including
marine,brackishand freshwater prawns , crabs, crayfish and lobsters .
• P.monodon, Macrobrachiumrosenbergii, P.japonicus, Fenneropenaeuschinensis,
L.Vannamei, P.indicus , P.merguensis
• transmissionstudies of WSSV among individuals have demonstrated that
transmissions occur through horizontal(transmissionby direct contact or ingestion of
WSSV infected organisms) and vertical pathways (from an infected female brooder to
its offspring)
• Studies on the factors determining WSSV transmissionin shrimp have reported that an
abrupt drop in temperature and salinity due to heavy rain is a hazard factor for a WSSV
outbreak.
• Larvae and early post-larvae of P. monodonwere reported to resist to a WSSV infection
by immersionand oral infection; further stages (late post-lavae and adults) were found
more susceptible to WSSV challenge.
• Further, shrimp are more susceptibly to WSSV infection via immersionshortly after
molting than in the period before molting
HOST RANGE AND WSSV TRANSMISSION

7. WSSV infections in penaeid shrimp conducted
so far have suggested that WSSV target cells
can be found in organs of both ectodermal
and mesodermalorigin.
i. Cuticular epithelium
ii. epidermis,gills , anten
iii. The lymphoidorgan , muscle
iv. Heart ,eyestalk,gonads,
v. Haematopoietic tissue
vi. Stomach cuticular epidermis
vii. Sub cuticular connective tissue
viii. Antennal gland ,hind gut and foregut
ix. Nervous system and compound eyes are
infected in very late stage
TARGET TISSUES FOR WSSV IN SHRIMP

8. • farmers often report WSS symptoms, which appear in ponds “30-60 days”
poststocking. When disease occurs, WSSV-infected shrimp “gather near the
border of the pond”.
• Cumulative mortality may reach up to 100% within 10 days after the first mortalities
occur.
• Shrimp infected with WSSV often show white spots with a diameter of 0.5 to 3.0 mm
in the exoskeleton of the carapace, appendages and body.
• Other signs like : lethargy,Sudden reduction of feed consumption, red discoloration
of body and loose cuticle.
• identification of a WSSV infection cannot be based solely on the presence of these
white spots. Several methods have been developed for the diagnosis of WSS in
shrimp: “histopathology, transmission electron microscope, DNA and
immunostaining”.
• Histopathology has a low sensitivity to detect WSSV-infected hosts at the early
stage of infection.
8
CLINICAL SIGNS AND DIAGNOSTIC TECHNIQUES

9. • DNA based techniques including in situ hybridization, PCR, nested-PCR, in
situ PCR and qPCR have been widely used and became powerful tools to
detect the WSSV genome in WSSV-infected animals.
• These DNA based techniques are much more sensitive than histology and
have been used for the early detection of WSSV infection.
HISTOLOGY PROCEDURE Eg;
9
FIXATION
TISSUE
PROCESSING
TISSUE
EMBEDDING
SECTIONING STAINING

12. “There is no treatment for WSSV. Prevention is the only way to avoid the
disease”
• No effective Vaccination methods for wssv have been developed
• Other elements such as sulphated polysaccharides, fucoidan, microalgae cell
walls have been used as “immunostimulants” for shrimp.
• These products have been somewhat successful againstpathogens like wssv
around the world
• Chemotherapy no scientifically confirmed reports.
• Low temperatures (12± 2°) affect the wssv pathogenicity and inhibit mortality
in shrimp.
CONTROL AND PREVENTION

13. • As avoidingstocking in the “cold seasonspf free larvae” in the culture
system
• B-1,3-glucan, whose addition to the shrimp “feed” effectively improves
the immunity and survival ofP.monodon.
• Some products such as “Dunaliella extract” and “probiotics” show a
positive effect on resistance of shrimp towssv infection.
• WSSV can persist in wet soil. Carry out pond preparation properly by
drying, applying lime etc. Provide sufficient time of at least three to four
weeks between the culture cycles to enable the pond soil to completely
dry
PROPHLACTIC

14.  Stock only post larvae (PL) of at least “PL15” stage. Select healthy PL using stress
tests and make sure that the PL are negative for WSSV by PCR testing.
 Adopt strict “biosecurity” measures by providingreservoirponds, birdand crab
fencing, proper s a n i t a t i o n o f m e n , material and machines.
 Adopt “best management practice” (BMP)to maintain good water quality, proper
feed usages and good health of shrimps through regular monitoring.
 Usagesof “probiotics” and“immunostimulant” may be helpful. However, avoid using
too many chemicals/ unauthorised products without knowing their exact effect.
 Government and private laboratories are availablefor PCR testing of WSSV. Liveand
moribund samplescollected in ethyl alcohol can be sent to these laboratories for WSSV
testing.

15. “Prevention is better than cure”
Finally, The development of good management practices,
control of environmentalvariables,genetic improvement in
the penaeid species, understanding of virus physiology,
modulation of the shrimp immune system, can reduce the
epizootics. To Sustainable Aquaculture in Future.
CONCLUSION

16. • Prevention & Management of white spot disease of shrimp - Ciba Extension Series No.
: 51 .,2016.
• Gunalan, B., Soundarapandian, P., & Dinakaran, G. K. (2010). The effect of
temperature and pH on WSSV infection in cultured marine shrimp Penaeus monodon
(Fabricius). Middle East Journal of Scientific Research, 5(1), 28-33.
• Balakrishnan, G., Peyail, S., Kumaran, R., Theivasigamani, A., Anil, K. S., Jitesh, S.
B., & Srinivasan, N. (2011). First report on White Spot Syndrome Virus (WSSV)
infection in white leg shrimp Litopenaeus vannamei (Crustacea, Penaeidae) under semi
intensive culture condition in India. Aquaculture, Aquarium, Conservation &
Legislation, 4(3), 301-305.
• Khuong, T. V. (2016). Experimental studies on the portal of entry of White spot
syndrome virus in Penaeus vannamei (Doctoral dissertation, Ghent University).
• Vidal, O. M., Granja, C. B., Aranguren, F., Brock, J. A., & Salazar, M. (2001). A
profound effect of hyperthermia on survival of Litopenaeus vannamei juveniles
infected with white spot syndrome virus. Journal of the world aquaculture
society, 32(4), 364-372.
REFERENCE

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