Another disease that caused substantial economic losses in shrimp
culture was white spot disease, caused by white spot syndrome virus
(WSSV),which had occurred on five farms (Table 3) within the previous
12 months. Farmers diagnosed WSSV when white spots appeared on
the cephalothorax and abdominal exoskeleton and the shell was easy
to peel off. Immediately after a WSSV disease outbreak, most farmers
did an early harvest as the shrimp would usually die within a few days.
The so-called “secret death disease” was reported by 5/30 shrimp
farmers. The shrimp initially decreased or ceased their feed intake
which was quickly followed by high mortalities around one month
post-stocking (Table 3). Farmers found it difficult to diagnose “secret
death disease” which typically occurred within 30–60 days after stocking
with subsequent mortalities of around 70%.