Shrimp disease guide - White Spot Disease

White Spot Disease (WSD), also known as infection with White Spot Syndrome Virus (WSSV), is a highly contagious viral disease of prawns that causes high rates of mortality in affected stock. Other crustaceans can be carriers of the virus, but they are rarely impacted by the disease. WSD poses no threat to human health or food safety.

White spot lesions. Photo courtesy of the Queensland Department of Agriculture and Fisheries

WSD spread through Asian prawn farming regions rapidly in the 1990’s and also became established in in farmed prawn in the Americas causing widespread losses.

What are the characteristics of White Spot Disease?

Signs of White Spot Disease in aquaculture within tanks and ponds include:

⦁ rapid onset of mass mortality (80% or more) in farmed penaeid prawns during the grow out period

⦁ lethargy

⦁ cessation of feeding

⦁ aggregations of moribund prawns near the water surface at the edge of the rearing pond or tank

Prawns may display:

⦁ a loose carapace

⦁ high degrees of colour variation, with a predominance of darkened (red-brown or pink) body surface and appendages

⦁ white calcium deposits embedded in the shell, causing white spots 0.5 – 3.0 mm in diameter