TÓM TẮT NỘI DUNG:

Several bacterial species of Vibrio genus are usually pathogens to marine cultured animals. Vibrio owensii strain DY05 has just recently been demonstrated as an agent of disease causing rapid and high mortality in phyllosoma larva of ornate spiny lobster (Panulirus ornatus) cultured in Australia. This study aims to determine the infection effect of V. owensii DY05 on the mortality rate of spiny lobster juveniles cultured at the lab scale in Vietnam. Loster juveniles were cultured in 6 tanks with 10 individuals (12-15 g each) per tank. Lobsters were exposed to DY05 at 10 3, 10 4, 10 5 , 10 6 and 10 7 CFU.ml-1 dosages (Tank A, B, C, D, and E, respectively) using direct immersion. Tank F without bacterial infection was used as control. After 20 infection days, mortality rates in tanks A, B, C, D, E and F were 0, 20, 25, 55, 85 and 0 (%), respectively. Specific death signs were observed including no eating 2 – 3 days before the dealth, slow movement, red tail and abdomen. V. owensii DY05 was virulent to lobster juvenile at LD 50 10 5.833 CFU.ml -1. The cell counts of total Vibrio reisolated from dead lobsters were 3.5×10 3 to 7.1×10 3 (CFU.g -1 ). Histopathological examination on dead lobsters showed necrotic hepatopancreas tubules and broken thoracic musculature bond. The results suggest that V. owensii DY05 may be a pathogen in ornate spiny lobster juvenile in the condition of this study. This is the first report on experimental infection of V. owensii DY05 on postlarval spiny lobsters.