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WSSV (White Spot Syndrome Virus) (causes white spot disease (Size…
WSSV (White Spot Syndrome Virus)
causes white spot disease
Family: Nimaviridae
Structure: Baciliform
Genus: Whispovirus
Size
Diameter-120-150nm
Length-270-290nm
:sparkles:Flagella-like appendage-end of virion
:sparkles:wide range of host- :fried_shrimp:penaieds, :crab:crabs : and :fish_cake:crayfish
:sparkles:All life stages-eggs to brookstock are susceptible
:sparkles:Best target organs- tissues of ectodermal and mesodermal embryonic origin exp
:star:cuticular epithelium
:star:subcuticular connective tissue
Prevalence
: :explode:1% (wild population)
:explode:100%(captive population)
SYMPTOMS
Clinical signs
:white_flower:white spot embedded within the exoskeleton(barely visible to 3mm diameter
:white_flower:environmental stress cause the higher alkanity & bacterial disease
:white_flower:diseased pop:pinkish or reddish discoloured population
Behavioural changes
:small_red_triangle:lethargic-colour changes to pink or reddish-brown :bread:
:small_red_triangle:loss of appetite
:small_red_triangle:bottom of pond
:small_red_triangle:high mortality rate-(in a few hours to days of onset :clock5:
DIAGNOSIS
Histology
-demonstration of inclusion bodies :meat_on_bone:
EM
-Demonstration of the virus :video_game:
:sweat_drops:
Wet mounts-
:microscope:microscopic
:black_square_for_stop:squash preparation of the gills and/or cuticular epithelium
PCR
:heavy_plus_sign:Positive in primary raection-serious infection
:heavy_plus_sign:Positive in secondary reaction-latent/carrier infection
:recycle:Two-step PCR+sequencing : recommended method for declaring freedom, only juveniles and adults and possibly PLs
:recycle:Two-step PCR :heavy_minus_sign:negative results are required
:recycle:Two-step PCR :heavy_plus_sign: positive results cannot be confirmed sequencing, this also counts negative :heavy_minus_sign: results
WSSV can be isolated from primary cultures of lymphoid or ovary cells
:arrow_down:
not recommended
WHY????????
:hammer_and_pick:high risk of contamination
:champagne:composition of the medium varies depending on the tissue type
:card_index_dividers::host species and experimental purpose
:reminder_ribbon::no standard or recognised medium
CONTROL AND PREVENTION
:<3:Vaccination
:<3:Vaccinated shrimp :shrimp:-shown better survival rate
:four_leaf_clover:Immunostimulatent (beta glucan, vit C, seaweed extrac)ts
:egg:Disinfection of eggs and larvae
:sunflower:
General husbandry practices
:cold_sweat:avoiding stocking in the cold season
:free:use of specific pathogen free (SPF)
PCR :heavy_minus_sign:negatives seed stocks
:droplet: use of biosecure water and culture system