Incidence of running mortality syndrome (RMS) in Pacific whiteleg shrimp, Litopenaeus vannamei, in an intensive biofloc grow-out pond

Bacterial disease is a major problem in Pacific whiteleg shrimp, Litopenaeus vannamei farming areas where farmers are facing a huge production loss due to epidemic diseases. The incidence of running mortality syndrome (RMS) was reported in L. vannamei, in an intensive biofloc culture system. Infected shrimps showed bacterial spots on the surface of the carapace, thick transparent mucous attached to the hepatopancreas, antennal cut, and cannibalism. Microscopical examination revealed a lichen-like structure with undulated margins varying about 22-650 µm size. Morphological characteristics of the colonies were smooth, circular, and opaque. Histopathological studies showed the sloughing of the tubule, multiplication of the bacterial plaque, and infiltration of the hemocytes in the infected hepatopancreas. Scanning electron microscopy of the infected shrimp revealed bacilli and cocci-shaped bacteria. Using transmission electron microscopy, bacterial populations were observed in the cytoplasm.