Probiotics in shellfish aquaculture

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.

https://link.springer.com/content/pdf/10.1007/s42995-020-00037-z.pdf

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

Vibriosis in cultured marine fishes: a review

Structure of fish Toll-like receptors (TLR) and NOD-like receptors (NLR)

Probiotics, prebiotics, and synbiotics used to control vibriosis in fish: A review

Current growth in aquaculture production is parallel with the increasing number of disease outbreaks, which negatively affect the production, profitability, and sustainability of the global aquaculture industry. Vibriosis is among the most common diseases leading to massive mortality of cultured shrimp, fish, and shellfish in Asia. High incidence of vibriosis can occur in hatchery and grow-out facilities, but juveniles are more susceptible to the disease. Various factors, particularly the source of fish, environmental factors (including water quality and farm management), and the virulence factors of Vibrio, influence the occurrence of the disease. Affected fish show weariness, with necrosis of skin and appendages, leading to body malformation, slow growth, internal organ liquefaction, blindness, muscle opacity, and mortality. A combination of control measures, particularly a disease-free source of fish, biosecurity of the farm, improved water quality, and other preventive measures (e.g., vaccination) might be able to control the infection. Although some control measures are expensive and less practical, vaccination is effective, relatively cheap, and easily implemented. In this review, the latest knowledge on the pathogenesis and control of vibriosis, including vaccination, is discussed.

/pdf/vibriosis-in-fish-a-review-on-disease-development-and-4notmr5m0l.pdf

Vibriosis in Fish: A Review on Disease Development and Prevention

Fish diseases are often caused either by bacteria, viruses, fungi, parasites, or a combination of these pathogens. Of these, bacterial fish diseases are considered to be a major problem in the aquaculture industry. Hence, the prevention of such diseases by proper vaccination is one of the integral strategies in fish health management, aimed at reducing the fish mortality rate in the aquaculture farms. Vaccination offers an effective yet low-cost solution to combat the risk of disease in fish farming. An appropriate vaccination regime to prevent bacterial diseases offers a solution against the harmful effects of antibiotic applications. This review discusses the role of live-attenuated vaccine in controlling bacterial diseases and the development of such vaccines and their vaccination strategy. The current achievements and potential applications of live-attenuated and combined vaccines are also highlighted. Vaccine development is concluded to be a demanding process, as it must satisfy the requirements of the aquaculture industry.

/pdf/live-vaccines-against-bacterial-fish-diseases-a-review-1jm04rb2df.pdf

Live vaccines against bacterial fish diseases: A review.

Grouper aquaculture industries have a high risk of being inflicted by bacterial diseases such as vibriosis. Various types of vaccines for vibriosis have been studied throughout the years, yet the potential of live attenuated vaccines remains unsubstantial. Correspondingly, this study attempts to develop a Vibrio harveyi protease deletion mutant into a live attenuated vaccine candidate against vibriosis for Epinephelus fuscoguttatus. Site-directed mutagenesis (SDM) and allelic exchange replacement techniques are employed to synthesize genetically attenuated V. harveyi strain MVh-vhs. The evaluation on safety levels showed that MVh-vhs strain is safe when tested on E. fuscoguttatus. A 100% survival rate with no sign of vibriosis is indicated in fish challenged with the attenuated strain. In contrast, fish challenged with the parental strain showed obvious clinical signs of vibriosis. The median lethal dosage (LD50) of fish challenged with the parental strain is found at 106 CFU/fish. A single dose IP administration of the attenuated strain at 105 CFU/fish following a bacterial challenge at dose 108 CFU/fish is done 4 weeks post vaccination. The vaccinated fish show 52% relative percentage survival (RPS). The transcriptomic profiling following vaccination evoked the regulation of autophagosome pathway and the coagulation and complement cascade pathways as well as antigen processing and presentation pathways. As a conclusion, the V. harveyi attenuated strain MVh-vhs has significant potential to be applied as a live vaccine candidate against vibriosis for E. fuscoguttatus.

/pdf/vibrio-harveyi-protease-deletion-mutant-as-a-live-attenuated-17dkt6qf0c.pdf

Vibrio harveyi protease deletion mutant as a live attenuated vaccine candidate against vibriosis and transcriptome profiling following vaccination for Epinephelus fuscoguttatus

Vibrio harveyi causes vibriosis in various marine aquaculture fish species, especially when they are young. The infection subsequently leads to significant economic losses for aquaculture farms. Vaccination is recommended to control this disease. This study describes the efficacy of a live attenuated V. harveyi strain MVh_vhs (LAVh) as a vaccine candidate in controlling infection by wild‐type V. harveyi (WTVh) in Lates calcarifer. A total of 240 fingerlings were divided into four groups. Group 1 was not vaccinated and was not challenged, Group 2 was vaccinated with a formalin‐killed V. harveyi (FKVh), Group 3 was vaccinated with the LAVh before challenge and Group 4 was not vaccinated and was challenged. Bath vaccination was employed for one hour before the LAVh distribution was determined in the fish mucus, gill, liver, gut, kidney and spleen. The gills, livers, kidneys and skins were also sampled for gene expression analysis. To challenge the fish, skin abrasion was conducted before the fish were challenged by immersion with WTVh. The results revealed an extensive distribution of the LAVh in the liver and kidneys of the fish in Group 3 for the first 12 hr, resulting in mild lesions compared with Group 1. Similarly, there were significantly (p < .05) higher expressions of the Chemokine ligand 4 and major histocompatibility complex I genes in the skin and liver of the fish in Group 3 in comparison with other groups. Vaccination with LAVh resulted in a significantly high rate of survival (68%) of the fingerlings after being challenged with WTVh.

/pdf/efficacy-of-bath-vaccination-with-a-live-attenuated-vibrio-1sr1tgl0f7.pdf

Aslizah Mohd-Aris

Papers

Vibriosis in Fish: A Review on Disease Development and Prevention

Live vaccines against bacterial fish diseases: A review.

Vibrio harveyi protease deletion mutant as a live attenuated vaccine candidate against vibriosis and transcriptome profiling following vaccination for Epinephelus fuscoguttatus

Efficacy of bath vaccination with a live attenuated Vibrio harveyi against vibriosis in Asian seabass fingerling, Lates calcarifer