Gross anatomical findings from the fall 2008 Bonaire moray eel mortalities
Unexplained moray eel mortalities have been occurring in Bonaire since July 2008. The number of mortalities increased over time, peaking in October and sharply declining in November. Eel die-offs have occurred in Bonaire in the past and there are reports of eel die-offs in the wild populations but no causative agent has been identified. Mass eel die-offs in aquaculture facilities have been recorded for decades. Only within the past three decades has a causative agent been isolated and studied. This pathogen, Vibrio vulnificus serovar E, is considered primarily an eel pathogen but has been reported in several cases to infect humans. At the CIEE Research Facility, necropsies have been performed on twenty-three eel specimens. The eels have had several gross and microscopic abnormalities in common. For example, all had a hemorrhagic gastrointestinal tract and no outward signs of disease. Various parasites were noted in the swim bladder and GI tract. In many of the specimens, the liver was pale in color and the swim bladder contained a thick viscous material. Based upon these observations and clinical signs of V. vulnificus infection in eels, it is hypothesized that this bacterium is likely the causative agent responsible for the mass die-off of moray eels. However, diagnosis is dependent on testing at a laboratory using genetic or microbial techniques.