Current New Diseases ceasing the growth of Shrimp and factors arresting Shrimp DOC (Days of Culture) – Their Signs, Infectivity, Pathology and Treatment.-
Prevention and treatment of White Feces Disease (WFD) in Shrimp
White feces disease (WFD) is one of the most serious problems in shrimp culture. WFD on L. vannamei shrimp farming is currently causing lower productivity.
WFD becomes apparent when the digestive system of shrimp malfunctions and feces turns from normal (brownish color) to pale white color. White feces appear to be more buoyant than normal feces and float on the water surface. Shrimp hepatopancreas becomes whitish and soft. Farmers have observed that as soon as they see white feces, shrimp eat less. Early disease indications appear in both feed trays and at water surface, where abundant floating fecal strings white to some-what yellow feces are observed (Fig.1) and sometimes could also be found on feeding trays. Diseased shrimp tend to be darker in color and after some time their bodies will lose firmness and become soft and limp, and eventually will die. White feces disease often occurs one - two months after stocking and is manifested as reduced feed intake and feed absorption in the shrimp’s gut.
WFD has caused significant economic losses to shrimp farmers, because of high FCR, slow growth, and variable sizes of shrimp at harvest.
Fig.1. Water surface and pond edge of a Litopenaeus vannamei culture affected by white feces disease.
Signs and symptoms of WFD in shrimp:
Dark discoloration of the gills (Fig. 2)
Hepatopancreas and gut become white and pale in colour.
Fig. 3. Comparison of healthy shrimp (left) to WFD infected shrimp (right)
Fig. 4. Shell loss effect of WFD, left: anormal shrimp, right: loose shell
Main causes of WFD (the exact cause is still unclear)
1. Pathogenic factors
Bacteria: Vibrio spp. within hepatopancreas and midgut (Figs. 5)
Tcbs Agar detects vibrio