Trout Industry Research Articles

MK-0608 inhibits in vitro and in vivo RNA replication of infectious pancreatic necrosis virus

Infectious pancreatic necrosis virus (IPNV) is an important pathogen that is threatening the worldwide salmon and trout industry. But there is no therapeutic drug available for now. In this study, we demonstrate that MK-0608 is highly efficient against IPNV and low cytotoxic, with a 50 % effective concentration (EC50) of 0.20 μM and selectivity index (SI) of about 268. Time of addition assay illustrated that MK-0608 targeted the early stage of IPNV life cycle. Furthermore, we found that MK-0608 blocked IPNV attachment on the premise of sufficient pre-incubation time but MK-0608 did not influence viral internalization and release. MK-0608 could inhibit IPNV genome synthesis, and combination with ribavirin enhanced the inhibition effect, which might be functional via binding to IPNV RNA dependent RNA polymerase (RdRp), which was predicted by using molecular docking methods. In vivo test showed that IPNV was extremely suppressed in the rainbow trout (Oncorhynchus mykiss) with one single dose of MK-0608, and the higher dosage of 50 mg/kg could cause 3 log decrease of IPNV loads in fish tissues.

Host miR-146a-3p Facilitates Replication of Infectious Hematopoietic Necrosis Virus by Targeting WNT3a and CCND1.

Infectious hematopoietic necrosis virus (IHNV) is a serious pathogen that causes great economic loss to the salmon and trout industry. Previous studies showed that IHNV alters the expression patterns of splenic microRNAs (miRNAs) in rainbow trout. Among the differentially expressed miRNAs, miRNA146a-3p was upregulated by IHNV. However, it is unclear how IHNV utilizes miRNA146a-3p to escape the immune response or promote viral replication. The present study suggested that one multiplicity of infection (MOI) of IHNV induced the most significant miR-146a-3p expression at 1 day post infection (dpi). The upregulation of miR-146a-3p by IHNV was due to viral N, P, M, and G proteins and relied on the interferon (IFN) signaling pathway. Further investigation revealed that Wingless-type MMTV integration site family 3a (WNT3a) and G1/S-specific cyclin-D1-like (CCND1) are the target genes of miRNA-146a-3p. The regulation of IHNV infection by miRNA-146a-3p is dependent on WNT3a and CCND1. MiRNA-146a-3p was required for the downregulation of WNT3a and CCND1 by IHNV. Moreover, we also found that WNT3a and CCND1 are novel proteins that induce the type-I IFN response in RTG-2 cells, and both of them could inhibit the replication of IHNV. Therefore, IHNV-induced upregulation of miRNA-146a-3p promotes early viral replication by suppressing the type-I IFN response by targeting WNT3a and CCND1. This work not only reveals the molecular mechanism of miRNA-146a-3p during IHNV infection but also provides new antiviral targets for IHNV.

A new approach in rainbow trout (Oncorhynchus mykiss Walbaum, 1792) industry: "Turkish Salmon" production and marketing trends

With favorable environmental conditions and the adoption of new technologies, Türkiye has 1703 enterprises producing trout as of 2022. These enterprises collectively produce 167,286 tons of trout per year, including portioned fish (200-250 g), fillet candidates (400-600 g), and fillets (known as Turkish Salmon) (>3000 g). The production chain for Turkish Salmon involves hatcheries, dam lake net cage systems, and offshore net cage systems. There are 680 hatcheries producing trout eggs and fry, with a total annual production of 1,360,029,485 eggs. Additionally, 622 pond/dam lake net cage systems are used for producing Turkish Salmon candidates weighing 400-600 g, with a total production capacity of 163,525,079 kg per year. Offshore net cage systems in the Black Sea region, spread across six provinces, are utilized for Turkish Salmon production. Production planning is underway for two provinces, with a total planned production area of 15,650,000 m2 and a projected capacity of 221,188,000 kg per year. Türkiye is actively involved in the global aquaculture sector, paying close attention to its advancements. Türkiye has a strong egg/juvenile production capacity compared to other countries involved in trout production globally. However, the importation of biotechnology-applied and observed eggs continues, posing biological and genetic risks to Türkiye's natural aquatic areas. Over the past 20 years, Türkiye's trout production has grown significantly, reaching 167,286 tons per year, marking it as a significant food production industry. This success can be attributed to favorable environmental conditions, increasing consumer demand, the adoption of new technologies, and consistent investments. However, the rapid growth in the trout farming sector over the past five years has led to an uncontrollable decline in survival rates. This decline can be attributed to the spread of diseases, incorrect treatment methods, improper breeding management practices, flawed business management, unregulated fish transport, and compromised sanitary and environmental conditions.

The association of Lactococcus petauri with lactococcosis is older than expected

Lactococcosis is a globally prevalent infectious disease that has a significant economic and sanitary impact on the rainbow trout industry. Lactococcus garvieae has traditionally been considered the only species implicated in the etiology of this disease, but Lactococcus petauri, a new species, has recently been implicated as another etiological agent. Both species cannot be distinguished by routine methods commonly used in diagnostic laboratories, resulting in their misidentification. In the present study, the identification of 48 isolates initially identified as L. garvieae was studied by determining their in-silico DNA–DNA hybridization (dDDH) and average nucleotide identity (ANI) values using pairwise comparisons of their whole genome sequences and the genomes of the type strains of L. garvieae and L. petauri. The genome sequences of 37 isolates from countries in which lactococcosis can be considered endemic (Spain, Italy, Türkiye, and Greece) were obtained in this study, and the genomes of 11 isolates were retrieved from the GenBank database. Isolates from Italy, Singapore, Japan, South Korea, India, one Turkish isolate from 2013 and two Spanish isolates recovered in 1992 and 1996 were confirmed as L. garvieae. The remaining isolates from Spain and Türkiye, as well as those from Portugal, Israel, USA, and Greece were identified as L. petauri. Overall, 60.4% of isolates previously identified as L. garvieae were found to be L. petauri. These results confirm the implication of both species in the etiology of lactococcosis and suggest that L. petauri plays a significant role in the epidemiology of this disease. Some of the isolates identified as L. petauri in the present study were isolated three decades ago, indicating that its association with lactococcosis is older than might be expected from the recent descriptions. The commercial Rapid ID32 Strep system was unable to discriminate between L. garvieae and L. petauri. However, both species exhibited some biochemical differences that might serve as phenotypic markers for their presumptive recognition. Consequently, isolates that hydrolyze hippurate and produce acid from sucrose and tagatose could be presumptively recognized as L. petauri, while those that fail these tests could be identified as L. garvieae. The results of this work indicate that great attention should be given to L. petauri in the epidemiology of lactococcosis.

Long-Term Protection Elicited by an Inactivated Vaccine Supplemented with a Water-Based Adjuvant against Infectious Hematopoietic Necrosis Virus in Rainbow Trout (Oncorhynchus mykiss).

Previous inactivated vaccines against infectious hematopoietic necrosis (IHN) usually had a strong early immune protective effect but failed to provide long-term protection in rainbow trout (Oncorhynchus mykiss). To find a method for stabilizing the desired protective effect of IHN vaccines, we assessed the immune enhancement effect of four adjuvants on formaldehyde inactivated vaccine for IHN at 60 days postvaccination (dpv). The efficacy of a two-dose vaccination with the candidate adjuvant-formaldehyde inactivated vaccine for IHN was evaluated in terms of early protection and long-term protection (30 to 285 dpv). Neutralizing antibody titers were also measured at each time point. The Montanide GEL 02 PR (Gel 02) adjuvant significantly enhanced the immune protection provided by the IHN inactivated vaccine, whereas the immune-boosting effect of the other tested adjuvants lacked statistical significance. Both tested Gel 02-adjuvanted IHN inactivated vaccine dosages had a strong immune protection effect within 2 months postvaccination, with a relative percent of survival (RPS) of 89.01% to 100%, and the higher dosage provided complete protection at 204 dpv and a RPS of 60.79% on 285 dpv by reducing viral titers in rainbow trout. The neutralizing antibodies were observed only in vaccinated fish on 30 and 60 dpv. Through compatibility with an appropriate adjuvant, the highly immune protective effect of an IHN inactivated vaccine was prolonged from 60 dpv to at least 284 dpv; this novel adjuvant-IHN inactivated vaccine has promise as a commercial vaccine that provides the best available and longest duration of protection against IHN to rainbow trout. IMPORTANCE Infectious hematopoietic necrosis virus (IHNV) is one of the most serious pathogens threatening the global salmon and trout industry. However, there is currently only one commercialized infectious hematopoietic necrosis (IHN) vaccine, and it is inadequate for solving the global IHN problem. In this study, a promising adjuvanted inactivated vaccine with long-term protection was developed and comprehensively studied. We confirmed the presence of a late antiviral response stage in vaccinated rainbow trout that lacked detectable neutralizing antibodies, which are commonly recognized to be responsible for long-term specific protection in mammals. These findings further our understanding of unique features of fish immune systems and could lead to improved prevention and control of fish diseases.

Two‐level trout supply chain's economic efficiency analysis in Iran: Trout egg import subsidies role

AbstractIran has subsidised trout egg imports due to the lower feed conversion ratio of most imported trout eggs. However, the rainbow trout industry is divided on whether to allocate or abolish imported trout subsidies. The elimination of such support would lead to a three‐fold rise in the price of imported trout eggs (which are already more expensive than domestic trout eggs). Furthermore, the economic performance of the domestic trout supply chain over the imported trout supply chain remains yet to be clarified. The present study seeks to evaluate whether imported trout egg subsidies should be continued. Economic efficiency and network data envelopment analysis are used to evaluate the performance and role of subsidies in trout supply chains in Mazandaran, one of the largest trout farming provinces as a new case study in the aquaculture sector, in 2018. Farms that used imported trout eggs were found to have lower economic efficiency and higher dependence on import subsidies. Feed costs were identified to be the most important explanation for poor economic efficiency of trout production. Finally, the results reveal that the development of domestic trout propagation supply chains with integrated forward vertical structures could improve efficiency in the system. The re‐distribution of imported trout egg subsidies to fund feed cost reduction technologies could provide effective solutions to enhance economic efficiency, production sustainability and food security.

MiR-301b-5p and its target gene nfatc2ip regulate inflammatory responses in the liver of rainbow trout (Oncorhynchus mykiss) under high temperature stress

Rainbow trout (Oncorhynchus mykiss) is a typical cold-water aquaculture fish and a high-end aquatic product. When water temperature exceeds its optimal range of 12–18 °C, the immune system of rainbow trout becomes weakened and unbalanced. High temperature in summer and global warming severely impact rainbow trout industry. The focus of this study was to explore the mechanisms regulating the immune response of rainbow trout under high temperature stress and identify molecular elements that account for resistance to high temperature. In this study, individual fish were screened in a high temperature stress experiment and divided into resistant (R) and sensitive (S) groups. The hepatic transcriptome sequencing and analysis of mRNAs and microRNAs of the R, S, and control groups showed that the number of the differentially expressed genes (DEGs) in the S group (9259) was higher than that in the R group (5313). Furthermore, the 1233 genes differentially expressed between S and R groups were mainly enriched in immune-related pathways, including cytokine-cytokine receptor interaction, TNF signaling and IL-17 signaling. Among these DEGs were miR-301b-5p and its target gene that encodes nuclear factor of activated T cells two interacting protein (nfatc2ip). The dual-luciferase reporter system and immunofluorescence experiments verified the relationship between miR-301b-5p and nfatc2ip. We also showed that expression levels of miR-301b-5p and nfatc2ip significantly negatively correlated in the liver of rainbow trout under high temperature stress. By performing functional experiments, we showed that activation of miR-301b-5p expression or inhibition of nfatc2ip expression stimulated the phosphorylation of p65, p38, and JNK in the classical nuclear factor kappa-B and mitogen-activated protein kinase pathways under high temperature stress. These manipulations initially promoted the secretion of the pro-inflammatory factor IL-1β and then increased the levels of IL-6, IL-12, and TNF-α. In addition, activation of miR-301b-5p expression or inhibition of nfatc2ip expression stimulated the repair of the hepatic ultrastructural damage caused by high temperature stress by activating the inflammatory response in rainbow trout liver.

Rapid Diagnostic Test to Detect and Discriminate Infectious Hematopoietic Necrosis Virus (IHNV) Genogroups U and M to Aid Management of Pacific Northwest Salmonid Populations.

Simple SummaryInfectious hematopoietic necrosis virus (IHNV) can cause severe disease and mortality in salmon and trout. Two major groups of the virus are found in the North American Columbia River Basin and Washington Coast, designated U and M. The U and M groups pose different risks depending on the fish host species. Here, we report the development of a new diagnostic test that can both detect the presence of IHNV and rapidly discriminate between the U and M groups. The new assay proved sensitive and specific when applied to free ranging, returning adult Pacific salmon. Infectious hematopoietic necrosis virus (IHNV) is an acute pathogen of salmonids in North America, Europe, and Asia that is phylogenetically classified into five major virus genogroups (U, M, L, E, and J). The geographic range of the U and M genogroup isolates overlap in the North American Columbia River Basin and Washington Coast region, where these genogroups pose different risks depending on the species of Pacific salmon (Oncorhynchus spp.). For certain management decisions, there is a need to both test for IHNV presence and rapidly determine the genogroup. Herein, we report the development and validation of a U/M multiplex reverse transcription, real-time PCR (RT-rPCR) assay targeting the IHNV nucleocapsid (N) protein gene. The new U/M RT-rPCR is a rapid, sensitive, and repeatable assay capable of specifically discriminating between North American U and M genogroup IHNV isolates. However, one M genogroup isolate obtained from commercially cultured Idaho rainbow trout (O. mykiss) showed reduced sensitivity with the RT-rPCR test, suggesting caution may be warranted before applying RT-rPCR as the sole surveillance test in areas associated with the Idaho trout industry. The new U/M assay had high diagnostic sensitivity (DSe > 94%) and specificity (DSp > 97%) in free-ranging adult Pacific salmon, when assessed relative to cell culture, the widely accepted reference standard, as well as the previously validated universal N RT-rPCR test. The high diagnostic performance of the new U/M assay indicates the test is suitable for surveillance, diagnosis, and confirmation of IHNV in Pacific salmon from the Pacific Northwest regions where the U and M genogroups overlap.

Experimental transmission of Caligus rogercresseyi between two different fish species.

Caligus rogercresseyi is the dominant sea louse parasite affecting the salmon and trout industry in southern Chile. This parasite has a wide range of native and endemic fish hosts. The Patagonian blenny Eleginops maclovinus, which is parasitized mostly by the caligid species Lepeophtheirus spp. and C. rogercresseyi, is presumably responsible for the transmission of C. rogercresseyi to salmonids. The aim of this study was to characterize the transmission of parasites between different fish species and parasite cohort development under laboratory conditions. Parasite abundances and intensities were quantified. Transmission of parasites from Patagonian blenny to Atlantic salmon Salmo salar was lower (~9%, mainly corresponding to C. rogercresseyi) than from salmon to Patagonian blenny (14.7-26.9%, where only C. rogercresseyi were observed). This suggests that the transmission of C. rogercresseyi from salmon individuals is higher than the transmission from a native fish. Parasite cohorts developed successfully on both fish species, but apparently under different developmental rates. Water temperature, oxygen, and juvenile abundances were the variables that better explained cohort development success and variation in C. rogercresseyi adult abundances over time.

VHSV Single Amino Acid Polymorphisms (SAPs) Associated With Virulence in Rainbow Trout.

The Viral Hemorrhagic Septicemia Virus (VHSV) is an OIE notifiable pathogen widespread in the Northern Hemisphere that encompasses four genotypes and nine subtypes. In Europe, subtype Ia impairs predominantly the rainbow trout industry causing severe rates of mortality, while other VHSV genotypes and subtypes affect a number of marine and freshwater species, both farmed and wild. VHSV has repeatedly proved to be able to jump to rainbow trout from the marine reservoir, causing mortality episodes. The molecular mechanisms regulating VHSV virulence and host tropism are not fully understood, mainly due to the scarce availability of complete genome sequences and information on the virulence phenotype. With the scope of identifying in silico molecular markers for VHSV virulence, we generated an extensive dataset of 55 viral genomes and related mortality data obtained from rainbow trout experimental challenges. Using statistical association analyses that combined genetic and mortality data, we found 38 single amino acid polymorphisms scattered throughout the complete coding regions of the viral genome that were putatively involved in virulence of VHSV in trout. Specific amino acid signatures were recognized as being associated with either low or high virulence phenotypes. The phylogenetic analysis of VHSV coding regions supported the evolution toward greater virulence in rainbow trout within subtype Ia, and identified several other subtypes which may be prone to be virulent for this species. This study sheds light on the molecular basis for VHSV virulence, and provides an extensive list of putative virulence markers for their subsequent validation.

Virulence of infectious pancreatic necrosis virus (IPNV) isolates from Mexico.

Infectious pancreatic necrosis virus (IPNV) causes economic losses in Mexican rainbow trout industry. In this study, virulence and genetic fingerprints of Mexican IPNV isolates was investigated for the first time. Two Mexican IPNV isolates were analyzed in rainbow trout fry and the Sp strain was included as high virulence. One of the Mexican IPNV isolate was obtained from diseased fish and the other from fish without clinical signs. The infection was performed using a standardized immersion. Clinical signs were observed at 4 days post infection in fry group infected with strain Sp, two days earlier than in trout infected with IPNV isolates Mexican. Severe lesions were found in 100% of the individuals of Sp group, but only in 25% of each isolated Mexican group. Results suggest that Mexican IPNV isolates are pathogenic, but less virulent than strain Sp. The amino acid motif residues of both Mexican isolates, corresponded to a subclinical disease. Nevertheless, the accumulated motility observed in the field, suggest that other factors play a role in the virulence of the disease.

Antimicrobial resistance and resistance genes in Flavobacterium psychrophilum isolates from Turkey

The antimicrobial susceptibilities of Turkish F. psychrophilum isolates were investigated using a Clinical and Laboratory Standards Institute (CLSI) standard microdilution testing protocol. The significance of the minimum inhibitory concentrations was determined by applying empirically and statistically determined epidemiological cut-off values calculated by normalized resistance analysis. Twenty-five F. psychrophilum isolates made over four years from three different trout species in five different regions were examined. All isolates were fully susceptible to amoxicillin and florfenicol, but 88% of our isolates were categorized as having reduced susceptibility to the two quinolones, oxolinic acid, and enrofloxacin. Eighty percent of the isolates were categorized as showing reduced susceptibility to oxytetracycline.Sequence analysis demonstrated that the reduced susceptibility to the quinolones was associated with chromosomal mutations in the gyrA and parE genes. PCR analysis demonstrated that the genes tetA, tetB, tetC, tetE, tetH, tetL, and tetM were not associated with the reduced susceptibility to oxytetracycline and the significance of this observation is discussed. PCR analysis also showed the presence of sul2 in six isolates and floR in one isolate. This study is the first report of these genes in F. psychrophilum. It was noted, however, that the floR was detected in an isolate categorized as fully susceptible to florfenicol, but the reasons for its lack of expression in the phenotype was not investigated.It is argued that the Turkish trout industry, in common with those of many countries world-wide, is critically dependent on the continued susceptibility of F. psychrophilum to florfenicol.

First detection and isolation of infectious haematopoietic necrosis virus from farmed rainbow trout in Nyeri County, Kenya.

Infectious haematopoietic necrosis virus (IHNV) is the causative agent of infectious haematopoietic necrosis, a disease of salmonid responsible for great economic losses. The disease occurs in most parts of the world where rainbow trout is reared but has not been previously reported in Kenya. In this study, rainbow trout fry and growers from two farms in Nyeri County were screened for IHNV. Whole fry (n=4 from each farm) and kidney samples from growers (n=15 and n=6 from the two farms, respectively) were collected and preserved for cell culture examination or PCR analysis. Screening of samples was done by PCR followed by sequencing of the glycoprotein gene of the virus. Demonstration of the virus was done by propagation in EPC cells followed by the indirect fluorescence antibody test (IFAT). The results revealed the presence of IHNV at low prevalence of 0.1 and 0.4 for the two farms. The virus was confirmed both by IFAT and by partial sequencing of the G gene. Phylogenetic analysis revealed that the Kenyan isolates were identical to those of the J genogroup found mostly in Asia. The findings have implications for biosecurity measures and import regulations for the Kenyan rainbow trout industry.

Prospects for feed use «Aller aqua» in the diet of rainbow trout

The materials of the article the analysis of periodic research reports on prospects of feed «Aller Aqua» in the diet of rainbow trout. Overview conceptual experience of increasing the volume of production of this important sector of agricultural production as the breeding and rearing of trout. Trout industry is the most productive direction of the coldwater aquaculture. Costs highly specialized feed for growing trout reach 70% of the total cost of the fish, so the features of feeding, nutritional feed and cultivation technology is relevant and of interest to manufacturers. Today on the Ukrainian market sales volume of feed for trout is a leading foreign firms: Aller Aqua, Biomar, Skretting and others. The quality of the manufactured products of domestic manufacturers often inferior to the requirements of the feed for trout, as domestic production is not always withstand competition. Therefore, at the present rate of trout industry as a promising field of fish farming, and the corresponding demand for feed for valuable fish species such high dependence on imports, now greatly reduces the volume of cold-water aquaculture cultivation sites that accordingly obliges producers special animal feed to improve their quality. The basis of our research is tasked with optimizing normalized using feeding trout feed «Aller Aqua» and results analysis and comparative characteristics of growing trout using Ukrainian feed manufacturers. Purpose is to clarify the nature of the impact of feed «Aller Aqua» and physiological metabolism, growth, development, reproduction and obtaining marketable products rainbow trout that could be the basis for conclusions about the appropriateness and use of feed rules «Aller Aqua», and the possibility of alternative feed means in terms of economy.

Molecular Evolution and Phylogeography of Co-circulating IHNV and VHSV in Italy.

Infectious haematopoietic necrosis virus (IHNV) and viral haemorrhagic septicaemia virus (VHSV) are the most important viral pathogens impacting rainbow trout farming. These viruses are persistent in Italy, where they are responsible for severe disease outbreaks (epizootics) that affect the profitability of the trout industry. Despite the importance of IHNV and VHSV, little is known about their evolution at a local scale, although this is likely to be important for virus eradication and control. To address this issue we performed a detailed molecular evolutionary and epidemiological analysis of IHNV and VHSV in trout farms from northern Italy. Full-length glycoprotein gene sequences of a selection of VHSV (n = 108) and IHNV (n = 89) strains were obtained. This revealed that Italian VHSV strains belong to sublineages Ia1 and Ia2 of genotype Ia and are distributed into 7 genetic clusters. In contrast, all Italian IHNV isolates fell within genogroup E, for which only a single genetic cluster was identified. More striking was that IHNV has evolved more rapidly than VHSV (mean rates of 11 and 7.3 × 10−4 nucleotide substitutions per site, per year, respectively), indicating that these viruses exhibit fundamentally different evolutionary dynamics. The time to the most recent common ancestor of both IHNV and VHSV was consistent with the first reports of these pathogens in Italy. By combining sequence data with epidemiological information it was possible to identify different patterns of virus spread among trout farms, in which adjacent facilities can be infected by either genetically similar or different viruses, and farms located in different water catchments can be infected by identical strains. Overall, these findings highlight the importance of combining molecular and epidemiological information to identify the determinants of IHN and VHS spread, and to provide data that is central to future surveillance strategies and possibly control.

Efficacy testing of a 35 year old commercially produced yersinia ruckeri bacterin for the control of enteric redmouth (ERM) disease

In 1976 the United States Department of Agriculture, Veterinary Services, granted the first veterinary product license for a biologic to be administered to fish. That license was issued for Enteric Redmouth Bacterin (Yerisina ruckeri) to the first commercial fish vaccine company, Wildlife Vaccines. This bacterin is widely used to control enteric redmouth disease (ERM). Licensed Y. ruckeri bacterins are administered to salmonid fish one gram in size and larger by immersion, automated immersion, showerspray and oral methods. At that time the most extensive use of Y. ruckeri bacterins were by the commercial rainbow trout industry located in southern Idaho. A 2 1⁄2 year program designed to evaluate the efficacy of immersion applied Y. ruckeri bacterins was initiated in 1978. Approximately 22 million fish were vaccinated under this program. Results obtained from this large scale field study of vaccinated and non-vaccinated fish demonstrated that mortality attributable to ERM disease as well as medicated feed requirements to treat this disease were significantly reduced. Feed conversion rates improved in vaccinated fish and as a direct result the time period required for rearing these fish was reduced. Recently, a bottle of ERM bacterin that was well over 30 years old and labeled by Wildlife Vaccines with a serial number of 236 and an expiration date of October 18, 1982 was discovered in a storage closet at room temperature at the Clear Springs Foods Research Division. In-vivo testing was initiated in juvenile rainbow trout (mean weight, 6 g) using the old Wildlife Vaccine product and an ERM vaccine produced in-house at Clear Springs. The vaccines were delivered to separate groups of fish by either immersion or injection and waterborne challenged with two doses of a virulent biotype 1 strain of Y. ruckeri 400 degree days post-vaccination.

Protection of rainbow trout (Onchorynchus mykiss L.) against Flavobacterium psychrophilum by immersion and injection vaccination using a novel polyvalent vaccine

Rainbow Trout Fry Syndrome (RTFS) is a disease caused by the Gram-negative bacterium Flavobacterium psychrophilum, responsible for economic losses in the trout industry worldwide. The diversity of F. psychrophilum strains, inherent difficulties in vaccinating juvenile fish and lack of a reproducible immersion challenge model has hampered the development of a vaccine for this disease. Disease episodes tend to occur between 10-14 oC, with necrotic lesions seen on the skin surrounding the dorsal fin and tail; in small fry often no clinical signs are apparent and death occurs due to septicaemia. At present no commercial vaccines are available, leaving antibiotics as the only course of action to contain disease outbreaks. The development of a vaccine is required, due to the potential risk of resistance developing in the antibiotics presently licensed for use in aquaculture.

Molecular characterization of Aquabirnaviruses isolated from farmed rainbow trout in Kenya

Event Abstract Back to Event Molecular characterization of Aquabirnaviruses isolated from farmed rainbow trout in Kenya Isaac Mulei1, 2*, Phillip Nyaga2, Paul Mbuthia2, Øystein Evensen1 and Stephen Mutoloki1 1 Norwegian University of Life Sciences, Basic Sciences and Aquatic Medicine, Norway 2 University of Nairobi, Department of Veterinary Pathology, Microbiology & Parasitology, Kenya Aquabirnaviruses are a diverse group of viruses within the family Birnaviridae. They include viruses from different species of fish, crustaceans and mollusks. Many of these viruses, such as infectious pancreatic necrosis virus (IPNV), cause serious diseases in a variety of fish species worldwide and have also been isolated from a variety of healthy freshwater and marine fish and shellfish. Rainbow trout (Oncorhynchus mykiss) were introduced to Kenya from Europe around the year 1920. They are reared in rivers in the high altitudes of Mount Kenya and Aberdares where temperatures are cool and the water is clean. Several fish farms have since been introduced along these rivers rearing rainbow trout. Further, the government has set up a rainbow trout hatchery in the high altitudes of Mt Kenya, harnessing water from river Chania, a tributary of the larger river Tana, which has its source from the top of the mountain. In order to meet their production requirements, some of the farms import fertilized eggs from the USA and Europe. It is well known that importation of breeding materials can be associated with the introduction of diseases and indeed, several of these farms are experiencing disease outbreaks. The objective of the present study was to investigate the presence of aquabirnaviruses in farmed rainbow trout in Kenya. 60 rainbow trout fish weighing approximately 250 gms were sampled from four farms by dip netting. The fish in groups of six were placed in polythene bags with aerated cold water and then transported by road to the lab where they were sacrificed and sampled. Organ collection included head kidneys, livers and spleens stored both in RNALater and transport medium. Screening of samples was done by RT-PCR and virus re-isolation. The prevalence of IPNV and phylogenetic relationships in comparison with isolates found in other parts of the world as well as the implication for the Kenyan rainbow trout industry will be presented and discussed. Acknowledgements This work was funded by NORAD through the Project "Capacity building for training and research in aquatic and environmental health in Eastern and Southern Africa" (TAN-13/0027). Keywords: Aquabirnavirus, Infectious pancreatic necrosis virus, rainbow trout, Kenya, Birnaviridae Infections Conference: AquaEpi I - 2016, Oslo, Norway, 20 Sep - 22 Sep, 2016. Presentation Type: Poster Topic: Aquatic Animal Epidemiology Citation: Mulei I, Nyaga P, Mbuthia P, Evensen Ø and Mutoloki S (2016). Molecular characterization of Aquabirnaviruses isolated from farmed rainbow trout in Kenya. Front. Vet. Sci. Conference Abstract: AquaEpi I - 2016. doi: 10.3389/conf.FVETS.2016.02.00009 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 17 Aug 2016; Published Online: 14 Sep 2016. * Correspondence: Dr. Isaac Mulei, Norwegian University of Life Sciences, Basic Sciences and Aquatic Medicine, Oslo, 0033, Norway, isaacmulei@yahoo.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Isaac Mulei Phillip Nyaga Paul Mbuthia Øystein Evensen Stephen Mutoloki Google Isaac Mulei Phillip Nyaga Paul Mbuthia Øystein Evensen Stephen Mutoloki Google Scholar Isaac Mulei Phillip Nyaga Paul Mbuthia Øystein Evensen Stephen Mutoloki PubMed Isaac Mulei Phillip Nyaga Paul Mbuthia Øystein Evensen Stephen Mutoloki Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Analysis on the development and current situation of rainbow trout (Oncorhynchus mykiss) farming in Mexico

AbstractThe rainbow trout (Oncorhynchus mykiss), originally from North America, was introduced to Mexico in 1888 and gradually distributed to various areas of the country. Currently, rainbow trout are cultivated in Mexico under a number of production systems, but this sector has grown less than 1% annually for the last 10 years. The present review analysed the production status of rainbow trout in Mexico, describing the key situations and actors that have influenced the establishment and current level of aquaculture development. Since its beginnings, rainbow trout cultivation in Mexico has depended on egg import due to insufficient egg and fry production by national hatcheries. Moreover, the industry is deficient in regard to a number of aspects in the production and management processes, with a notable necessity for specialists in the areas of production, health and sanitary diagnosis to rapidly and efficiently respond to situations such as low productivity or the presence of diseases. With such specialists, appropriate control and prevention decisions could be taken and acted upon. Likewise, the Mexican rainbow trout industry has high development potential and market expectations, but sector growth will require the active participation and commitment of competent authorities, in compliance with established Mexican regulations and laws, which are oriented towards advancing and protecting the fish farming industry.

Evaluation of long‐chain n3 fatty acid content in diploid and triploid rainbow trout

Intake of long chain n3 fatty acids (LCn3), eicosapentaenoic acid (EPA; 20:5 n3) and docosahexaenoic acid (DHA; 22:6 n3), is associated with reduced cardiovascular disease. There is growing interest in farmed fish like rainbow trout, Oncorhynchus mykiss, as sources of LCn3. The trout industry raises diploid (2N) and triploid (3N) fish. 3N females fail to sexually mature and avoid the negative effects of maturation on fillet quality. In this work we examined the LCn3 content of 2N and 3N trout. Female rainbow trout were selected from independent populations of 1 yr and 2 yr old 2N and 2 yr old 3N fish. Although each group consumed the same diet formulation, rearing conditions and feeding rates were different and only the 2 yr 2N trout were sexually mature. Boneless, skinless fillets were removed from 4 fish per group and the total fatty acid content of the fillets was determined by FAME analysis. The contents of LCn3 in the 3N 2yr trout (EPA: 1.9 ± 0.5 mg/g; DHA 7.6 ± 1.7 mg/g) were almost 2‐fold higher than in the 2N 2yr trout (EPA:0.8 ± 0. mg/g; DHA 3.9 ± 0.5 mg/g) and the 2N 1yr trout (EPA:1.0 ± 0.3 mg/g; DHA 4.0 ± 0.7 mg/g). The higher content of LCn3 was in part the result of total higher content of fatty acid in the 3N trout. The percent content of LCn3 and ratios of short chain to long chain n3 were similar in all groups. These data indicate that farm‐raised rainbow trout are a rich source of EPA and DHA. This work was supported by the USDA‐ARS.