Translucent Post Larvae Disease – a deadly Vibrio infection affecting farmed shrimp

Translucent Post Larvae Disease (TPD), also known as Highly Lethal Vibrio Disease (HLVD), represents a major threat to commercial shrimp hatcheries and nursery systems. The condition is primarily caused by a virulent strain of Vibrio parahaemolyticus carrying an aerolysin gene that produces toxins disrupting the hepatopancreas, although Baishivirus has also been implicated in some cases. Visually, affected post larvae (PL 2–4) present an empty gut and a translucent hepatopancreas, with mortalities rapidly reaching 80–100% within 24–48 hours, typically 3–5 days post-stocking. Because clinical symptoms mirror other vibrioses such as Acute Hepatopancreatic Necrosis Disease (AHPND) and Septic Hepatopancreatic Necrosis (SHPN), visual diagnosis is inadequate. Accurate identification requires molecular diagnostic methods, including nested PCR targeting toxin genes (pirAB for AHPND, ldh for TPD) or viral primers. Effective mitigation relies on strict hatchery biosecurity, water disinfection via ozone, UV, or hypochlorite, comprehensive pipeline cleaning to eliminate biofilms, pathogen-free live feeds, and probiotic application in rearing water and feed.