White Spot Disease
White Spot Syndrome Virus (WSSV)
Animal model: Whiteleg Shrimp
Applications: Anti-viral treatment, functional feeds, environmental treatments, immersion and in feed treatments, benchmarking commercial treatment efficies, genetic selection/phenotyping, dsRNA and other therapies
Type of model: Intramuscular (IM), per os
Clinical Signs of Disease in our Model: Loose cuticle, white spots inside of the carapace, lethargy
Challenge conditions: Salt water; 25-35C
Starting Fish Size: 0.5-15 grams
Shrimp aquaculture is a >30 billion dollar (USD) industry, producing >5 million tons of shrimp and prawns annually. Whiteleg shrimp, Litopanaeus vannamei, accounts for well over half of these production statistics and is primarily cultured in brackish ponds in Asia and South America. White spot syndrome virus (WSSV) is a highly transmissible virus affecting numerous crustaceans and is problematic in shrimp culture globally. Pond culture systems with high stocking densities promote WSSV multiplication and clinical disease, with rapid onset of mortality up to 100% within 3 to 10 days. White spot syndrome can be induced by stressful events associated with spawning, molting, or environmental changes, and is transmitted horizontally (waterborne routes and cannibalism) and vertically in hatcheries. Affected shrimp may present with clinical signs including a loose carapace, darkened body color, and/or white calcium deposits in the shell. Current strategies to manage the disease include maintenance of good environmental conditions and husbandry practices, and use of specific pathogen-free post-larvae. There is, however, no widely used prophylactic treatment that adequately prevents disease in an aquaculture environment.
At CAT, in vivo models for testing treatments for effectiveness in controlling morbidity and mortality associated with WSSV have been developed in Whiteleg shrimp (Litopenaues vannamei) using per os and intramuscular routes of infection. Trials can be executed via direct infection or by cohabitation and are offered for low, medium, and high infection pressure scenarios. Precise dosing of shrimp for highly controlled experiments is achieved via quantification of viral particles from WSSV-infected shrimp muscle homogenate using qPCR prior to injection, allowing for known copy number at the time of infection. Experiments designed to assess the safety and efficacy of novel products/treatments can be completed on isolated shrimp in individual tanks or using cohabitation, population-based infection models. An in vitro model using WSSV infected shrimp muscle homogenate is also available and can also be used for the determination of minimum inhibitory concentrations of viable WSSV in solution.