Viral Diseases In Aquaculture Research Articles

Broad-spectrum antiviral JL122 blocks infection and inhibits transmission of aquatic rhabdoviruses

The aquaculture industry is growing rapidly to meet the needs for global protein consumption. Viral diseases in aquaculture are quite challenging due to lack of treatment options as well as limited injection-delivery vaccines, which are costly. Thus, water-immersion antiviral treatments are highly desirable. This study focused on broad-spectrum, light-activated antivirals that target the viral membrane (envelope) of viruses to prevent viral-cell membrane fusion, ultimately blocking viral entry into cells. Of the tested small-molecules, JL122, a new broad-spectrum antiviral previously unexplored against aquatic viruses, blocked infection of three aquatic rhabdoviruses (IHNV, VHSV and SVCV) in cell culture and in two live fish challenge models. Importantly, JL122 inhibited transmission of IHNV from infected to uninfected rainbow trout. Further, the effective antiviral concentrations were not toxic to cells or susceptible fish. These results show promise for JL122 to become an immersion treatment option for outbreaks of aquatic enveloped viral infections.

Tilapia lake virus: a threat to the global tilapia industry?

AbstractTilapia lake virus (TiLV) is a recently described virus affecting wild and farmed tilapines. At present, it has been reported on three continents (Asia, Africa and South America) and the number of countries where the agent has been detected is likely to increase rapidly as a result of increased awareness, surveillance and availability of diagnostic methods. Any lack of openness regarding the TiLV status of a translocating live tilapia population destined for aquaculture may inadvertently contribute to the spread of the agent. Currently, there is no cure for viral diseases in aquaculture and while vaccines and selective breeding have proved successful in reducing the severity of some viral diseases, there are currently severe knowledge gaps relating to TiLV and no effective, affordable vaccines are yet available. This paper summarizes the published scientific information on TiLV and highlights important issues relating to its diagnosis, mitigation and control measures. While there have been no scientific studies on the socio‐economic impact of TiLV, it may pose a significant threat particularly to small‐scale fish farmers’ livelihoods and wild tilapine populations if left uncontrolled. To aid disease investigations, the authors propose case definitions for suspected and confirmed cases of TiLV infections.

Progress and limitations of dsRNA strategies in the control of viral diseases in aquaculture

The development of a sustainable aquaculture is consistent with a growing demand for new methods to ensure the health of various aquatic species. Among them, the use of revolutionary therapies based on double-stranded RNA (dsRNA) has opened a wide range of possibilities in the progress of the control strategies and disease prevention. The system of gene silencing by RNA interference (RNAi) has an interesting potential for the control of infectious diseases in aquaculture systems. On the other side, it has been found that dsRNA can have a significant immunomodulatory effect in fish cells, activating innate immune defense mechanisms. The definition of a suitable delivery system to ensure the entry of dsRNA to the target cell has results in moderately successful assays. However, the delivery of dsRNA to ensure the entry to the organism in its natural habitat is the main difficulty of this technology. This work presents a comprehensive review of potential post-transcriptional silencing by dsRNA as antiviral strategy in fish farming and its potential use as an immunostimulant, emphasizing the need to seek methodologies to deliver dsRNA into the target organism, considering the limitations and characteristics of a system of intensive farming.

Carbon nanotube-based nanocarrier loaded with ribavirin against grass carp reovirus

Infectious diseases of viral origin cause major aquatic production losses in different parts of the world. Because of formidable barriers for gastrointestinal tract, skin and cell, large amounts of antiviral drugs have limited therapeutic effect. In the current study, functionalized single-walled carbon nanotubes (SWCNTs) were selected as a drug carrier to carry antiviral drug for the treatment of viral diseases on fish. The results show that increasing antiviral drug (ribavirin) intake was observed by SWCNTs carrier and therapeutic dosage to kill grass carp reovirus is significantly reduced. At 12d post infection, survival rate and infection rate were 29.7% and 50.4% for naked ribavirin treatment group exposed to the highest concentration (20mg/L); however, survival rate of 96.6% and infection rate of 9.4% were observed in 5mg/L ribavirin-SWCNTs treatment group. In addition, the drug detention time in different organs and tissues (blood, gill, liver, muscle, kidney and intestine) was also significantly extended (about 72h) compared with the same dosage in naked ribavirin treatment group. Moreover, the toxicity of functionalized SWCNTs in grass carp can be minimal, and physiological markers (some antioxidant enzymes activities, apoptotic factors activities and their corresponding genes expression) remained within normal ranges following treatment. Our results indicated that drug delivery with functionalized SWCNTs can improve the antiviral effect on grass carp and has a potential application value to control fish viral diseases in aquaculture.

Development of methods for encapsulation of viruses into polymeric nano‐ and microparticles for aquaculture vaccines

ABSTRACTTo meet an urgent need for improved vaccines against viral diseases in aquaculture, encapsulating the viruses into biodegradable and biocompatible polymers was suggested to protect viral antigens from premature degradation and gradually expose them to the immune system. We used water‐in‐oil‐in‐water emulsion to first encapsulate model red fluorescent polystyrene (PS) particles and then infectious salmon anemia virus (ISAV) into poly‐lactic‐co‐glycolic acid (PLGA) together with coumarin 6. A milder layer‐by‐layer method was applied to incorporate both PS and ISAV into chitosan (Cs)‐fluorescein isothiocyanate and alginate (Alg) followed by ionic crosslinking. All particles were characterized by dynamic light scattering, zeta‐sizer, fluorescence, transmission‐ and scanning electron microscopy. Successful encapsulation of PS beads and ISAV into PLGA, Cs, and Alg was accomplished. The prepared particles were of different size, surface charge density, and morphology. This yields opportunities for further developments of these structures as vaccine candidates to be delivered by injection or oral administration. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40714.

A novel quantitative immunomagnetic reduction assay for Nervous necrosis virus

Rapid, sensitive, and automatic detection platforms are among the major approaches of controlling viral diseases in aquaculture. An efficient detection platform permits the monitoring of pathogen spread and helps to enhance the economic benefits of commercial aquaculture. Nervous necrosis virus (NNV), the cause of viral encephalopathy and retinopathy, is among the most devastating aquaculture viruses that infect marine fish species worldwide. In the present study, a highly sensitive magnetoreduction assay was developed for detecting target biomolecules with a primary focus on NNV antigens. A standard curve of the different NNV concentrations that were isolated from infected Malabar grouper (Epinephelus malabaricus) was established before experiments were conducted. The test solution was prepared by homogeneous dispersion of magnetic nanoparticles coated with rabbit anti-NNV antibody. The magnetic nanoparticles in the solution were oscillated by magnetic interaction with multiple externally applied, alternating current magnetic fields. The assay's limit of detection was approximately 2 × 10(1) TCID(50)/ml for NNV. Moreover, the immunomagnetic reduction readings for other aquatic viruses (i.e., 1 × 10(7) TCID(50)/ml for Infectious pancreatic necrosis virus and 1 × 10(6.5) TCID(50)/ml for grouper iridovirus) were below the background noise in the NNV solution, demonstrating the specificity of the new detection platform.

Can we get the upper hand on viral diseases in aquaculture of Atlantic salmon?

Viral diseases are a major problem in Atlantic salmon aquaculture. The development of more effective viral vaccines is crucial for a sustained control of viral diseases in salmon farming because the present viral vaccines are much less effective than the bacterial vaccines. On the other hand, research and lessons from Norwegian aquaculture suggest that major progress in the control of viral diseases can still be made through classical combat principles. Improved and enforced strategies for avoidance and control of viral pathogens by breaking horizontal transmission have yielded encouraging results both for the infectious salmon anaemia virus (ISAV) and for the pancreas disease virus (PDV). More emphasis should also be placed on the possible vertical transmission of viral pathogens. Interestingly, salmon appears to have a relatively strong innate immunity against viruses as it possesses a very well-developed interferon system. Interferons protect salmon cells very well against the infectious pancreatic necrosis (IPN) and PDV and salmon show high resistance against these viruses in challenge experiments. In contrast, these viruses cause high mortality in salmon farming. This suggests that the avoidance of production conditions that result in the suppression of the immune system is of primary importance for the prevention of IPN and PD in the aquaculture industry. Interferons protect salmon cells against the ISAV less effectively, which confirms that ISA must be combated by avoidance and vaccination. Breeding of virus-resistant salmon shows promising results, especially with respect to IPN. Finally, to effectuate the above combat principles, it is important to educate highly competent aquamedicine personnel within the aquaculture industry. In Norway, this is accomplished through a 5-year integrated MSc programme in Aquamedicine.

The outbreak of carp disease caused by CyHV‐3 as a model for new emerging viral diseases in aquaculture: a review

AbstractAquacultured koi and common carp (Cyprinus carpio) are intensively bred for ornamental purposes and for human consumption worldwide. The carp and koi farming industries have suffered enormous economic losses over the past decade due to an epizootic disease caused by Cyprinus herpesvirus‐3 (CyHV‐3) also known as koi herpesvirus and carp interstitial nephritis gill necrosis virus. CyHV‐3 is a large dsDNA virus, morphologically similar to herpesviruses, yet contains genetic elements similar to those of pox, irido‐ and herpesviruses. Considering the phylogenic distance between CyHV‐3 and higher vertebrate herpesviruses, CyHV‐3 represents the prototype of viruses assigned to the novel family Alloherpesviridae. Although emergence of a new virus rarely initiates a pandemic so severe that it reduces the life expectancy of a population, CyHV‐3 is exceptional because of its enormous impact on the world carp population. High population density is the major contributing factor to the epizootic disease caused by CyHV‐3.

Inhibition of red seabream iridovirus (RSIV) replication by small interfering RNA (siRNA) in a cell culture system

Small interfering RNAs (siRNAs), mediators of a process of sequence-specific gene silencing called RNA interference, have been shown to have activity against a wide range of viruses and are considered to be potential antiviral tools. Here, we describe an antiviral activity of a siRNA that targets the major capsid protein (MCP) gene of red seabream iridovirus (RSIV), a marine fish-pathogenic virus, in a cell culture system. Inhibition of RSIV replication was demonstrated by reduced MCP expression level and reduced RSIV titer. MCP-targeted siRNA (siR-MCP) dose-dependently inhibited the expression of MCP gene in cells that either transiently expressed or stably expressed the MCP gene. At 84 and 96h after viral infection, siR-MCP reduced the expression of MCP gene by 55.2% and 97.1%, respectively. Transfection with siR-MCP reduced the production of RSIV particles in supernatants of samples infected with RSIV, while the corresponding mismatched siR-MCP (MsiR-MCP) and nsRNA controls did not exhibit this effect. These results show that MCP-targeted siRNA can effectively and specifically inhibit the expression of the target gene and hinder RSIV replication during an in vitro infection, providing a potential approach for the control of viral diseases in aquaculture.