Lethal toxicity of Vibrio harveyi to cultivated Penaeus monodon induced by a bacteriophage

In Southern Thailand in 1996, intense luminescence in many shrimp rearing ponds was accompanied by massive mortality resulting in total crop loss within 3 or 4 d. Mortality was correlated with gross signs which shrimp farmers called (English translation) tea-brown gill syndrome (TBGS). Histological examination of moribund shrimp revealed massive lesions of the hepatopancreas characterized by hemocytic infiltration and the presence of bacterial cells. Bacterial isolation yielded several strains tentatively identified as Vibrio harveyi on the basis of luminescence and growth on BTB Teepol agar. Representative isolate VH1039 was selected and identified by biochemical tests as V. harveyi. When strain VH1039 and the other luminescent isolates were injected into normal shrimp (1 x 10 super(7) cells shrimp super(-1)), no significant mortality was observed in comparison with control shrimp injected without bacteria. Nor was any significant mortality observed after injection of supernatant fluids from normal or sonicated bacterial cultures of VH1039 (1 x 10 super(8) cells ml super(-1)). Transmission electron microscopy (TEM) of hepatopancreatic tissue from farmed TBGS shrimp revealed bacterial cells of Vibrio morphology together with large numbers of bacteriophage particles that had round to hexagonal heads of approximately 60 nm diameter and tails of approximately 100 nm length.