Vibrio harveyi: a serious pathogen of fish and invertebrates in mariculture

Abstract

Vibrio harveyi, which belongs to family Vibrionaceae of class Gammaproteobacteria, includes the species V. carchariae and V. trachuri as its junior synonyms. The organism is a well-recognized and serious bacterial pathogen of marine fish and invertebrates, including penaeid shrimp, in aquaculture. Diseased fish may exhibit a range of lesions, including eye lesions/blindness, gastro-enteritis, muscle necrosis, skin ulcers, and tail rot disease. In shrimp, V. harveyi is regarded as the etiological agent of luminous vibriosis in which affected animals glow in the dark. There is a second condition of shrimp known as Bolitas negricans where the digestive tract is filled with spheres of sloughed-off tissue. It is recognized that the pathogenicity mechanisms of V. harveyi may be different in fish and penaeid shrimp. In shrimp, the pathogenicity mechanisms involved the endotoxin lipopolysaccharide, and extracellular proteases, and interaction with bacteriophages. In fish, the pathogenicity mechanisms involved extracellular hemolysin (encoded by duplicate hemolysin genes), which was identified as a phospholipase B and could inactivate fish cells by apoptosis, via the caspase activation pathway. V. harveyi may enter the so-called viable but nonculturable (VBNC) state, and resuscitation of the VBNC cells may be an important reason for vibriosis outbreaks in aquaculture. Disease control measures center on dietary supplements (including probiotics), nonspecific immunostimulants, and vaccines and to a lesser extent antibiotics and other antimicrobial compounds.

Keywords: Aquaculture; Fish; Invertebrates; Pathogen; Vibrio harveyi.

Fig. 1

Morphology of Vibrio harveyi strains. a Growth of V. harveyi VIB 391 on marine agar 2216E; b luminescence of V. harveyi VIB 391; c growth of V. harveyi VIB 645 on TCBS agar; d transmission electron microscopy of VIB 645 cells obtained from marine broth culture. Scale = 1 μm

Fig. 2

Immunohistochemical localization of recombinant VHH from Vibrio harveyi in tissues of Japanese flounder injected with VHH. Rabbit anti-VHH antibody was used as primary antibody and horseradish peroxidase (HRP)-labeled goat anti-rabbit antibody was used as the secondary antibody. Positive staining (arrows) in intestine (a) and gill (b). Bar = 20 µm