White Spot Disease (WSD), has recently affected shrimp farms in Andhra Pradesh, with outbreaks detected through ongoing surveillance programs.
About White Spot Disease
White Spot Disease (WSD) is a highly contagious viral infection affecting shrimp and other crustaceans, caused by the White Spot Syndrome Virus (WSSV). It is one of the most devastating diseases in aquaculture, often leading to mass mortality within days.
Key Facts
- Causative Agent: White Spot Syndrome Virus (WSSV), a double-stranded DNA virus belonging to the genus Whispovirus and family Nimaviridae.
- Hosts: Primarily farmed shrimp (e.g., Penaeus monodon, Litopenaeus vannamei), but also crabs and other crustaceans.
- Symptoms:
- Circular white spots on the carapace and exoskeleton.
- Anorexia (loss of appetite) and lethargy.
- Reddish discoloration of the body.
- Rapid mortality (up to 80–90% within 5–7 days of onset).
- Transmission: Extremely fast spread via water, contaminated equipment, infected broodstock, and carriers like crabs.
Impact
- First major outbreak reported in Taiwan in 1992, later spreading across Asia, Latin America, and other shrimp-farming regions.
- Causes massive economic losses in aquaculture due to sudden crop failure.
Prevention & Control
There is no effective treatment once WSD appears, so prevention is critical:
- Biosecurity measures:
- Use pathogen-free broodstock and larvae.
- Disinfect ponds, equipment, and water sources.
- Prevent entry of carriers (wild crabs, insects).
- Monitoring: Regular PCR testing for WSSV in hatcheries and farms.
- Best practices: Maintain optimal water quality, avoid stress in shrimp, and follow strict quarantine protocols.
Risks & Challenges
- Rapid spread: Entire ponds can collapse in just a few days.
- Hidden infections: In some species (e.g., L. vannamei), white spots may not be visible, making detection harder.
- Global threat: WSD remains one of the most serious constraints to sustainable shrimp farming.
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