Infectious gastroenteritis caused by <i>Vibrio harveyi</i> (<i>V. carchariae</i>) in cultured red drum, <i>Sciaenops ocellatus</i>

Abstract

Summary An outbreak of serious mortality among the cultured red drum Sciaenops ocellatus (L.) characterized by a swollen intestine containing transparent yellow fluid (ascites and gastroenteritis) occurred in July 2000 in Taiwan. A motile strain Rd 0700 was isolated from head kidney and/or the intestinal yellow fluid on tryptone soya agar (TSA) supplemented with 2% (w/v) NaCl and/or thiosulfate citrate bile salt (TCBS) sucrose agar plates. Applying biochemical characteristics, this strain was characterized and identified as Vibrio harveyi (V. carchariae). The bacteria could be re-isolated from kidney, liver, and the transparent yellow fluid of swollen intestine of fish after bacterial challenge. The LD50 values of the organism and its extracellular products (ECP) were 2.9×107 colony forming units (CFU) and 3.85 μg protein g−1 fish body weight, respectively. All moribund/dead fish exhibited gastroenteritis except those killed within 12 h. This is a first report showing that intraperitoneal (i.p.) injection of the ECP from V. carchariae is lethal to red drum and can reproduce gastroenteritis in the fish.