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During recent years, there has been a renewed interest in establishing farming of Atlantic cod (Gadus morhua) in Norway. However, a fatal abdominal disorder compromises animal welfare and causes economic losses. A similar problem was present during a previous attempt to establish Atlantic cod farming more than a decade ago. In this paper, we provide the first in‐depth description of this intestinal disorder, which is correctly denoted 'strangulating obstruction'. In affected fish, part of the intestine is permanently entrapped (incarcerated) under fibrous strands in the mesentery. The entrapment interferes with blood flow and physically blocks the intestine, causing a strangulating obstruction with severe venous congestion and ischemia of the intestinal wall. Furthermore, comparison of macroscopical and histological anatomy of farmed and wild Atlantic cod is presented and risk factors associated with the anatomical differences are discussed. [ABSTRACT FROM AUTHOR]

The recent advances in molecular methods and data processing have facilitated research on anisakid nematodes. While most research efforts were made regarding the genus Anisakis, since this genus is held responsible for the majority of reported clinical signs, there is still a demand for data on the genus Pseudoterranova. Several case studies of severe invasive anisakidosis affecting various organs caused by species of the P. decipiens complex have been described. To better understand the way these parasites might infest their fish host, we examined whether parasite location within the fish host affects gene expression. A de novo assembly of the transcriptome of Pseudoterranova bulbosa, isolated from North Atlantic cod, was analysed for patterns of differential gene expression between samples taken from liver and viscera. We additionally searched for homologs to known nematode allergens, to give a first estimate of the potential allergenicity of P. bulbosa. There was a subtle difference in the gene expression of samples taken from liver and viscera. Seventy genes were differentially expressed, 32 genes were upregulated in parasites isolated from liver and 38 genes were upregulated in parasites from viscera. Homologs of five nematode allergens were identified among the genes expressed by P. bulbosa. Our transcriptome of P. bulbosa will be a valuable resource for further meta‐analyses and resequencing projects. [ABSTRACT FROM AUTHOR]

Similar to other vertebrates, teleost eyes have inverted retinas (Farrell et al., [10]; Kröger & Biehlmaier, [15]). However, unilateral pseudobranchectomies did not change visual pigment densities in ipsilateral and contralateral eyes, and oxygen partial pressure was shown to have decreased in the ipsilateral eye such that it was comparable to the contralateral eye, thus resolving the exophthalmos. Of these cases, 52.6% of patients presented with exophthalmia of the right eye (OD [oculus dextrus]), 26.3% presented with exophthalmia of the left eye (OS [oculus sinister]), 10.5% with exophthalmia of both left and right eyes (OU [oculus uterque]) and 10.5% with unilateral exophthalmia where the affected eye was not specified (unknown). Eyes were pretreated with ophthalmic antibiotics (Figure), typically ofloxacin (Bausch & Lomb Inc.), before aspirating gas from the adnexa, eye or retrobulbar areas using a 27-gauge needle in order to restore the eye to its natural shape and position (Figure). [Extracted from the article]

Although spinal injuries in fish have been associated with electric stimuli applied during electrofishing and electrotrawling, bone fracture and repair in the axial skeleton have yet not been studied. To study this, we radiographed a group (n = 64) of individually tagged farmed cod twice, with a 1‐year interval (∼36 cm at first and ∼ 50 cm at second inspection). The study focus was on the neural and haemal spines. These structures are un‐paired and are not covered by other bones laterally, making them useful for radiological studies on axial skeletal fracture in live fish. At the first examination, four animals showed radiological changes in their neural and haemal spines. Two animals had fractures, and two had callus formations. One year later, at the second radiological examination, the fractures had developed into calluses or into normal morphology, and calluses either remained as calluses or had developed into normal morphology. A further 14 animals that were all normal at the first inspection had developed changes in their neural and haemal spines, both fractures and callus formations. This is the first record of spontaneous bone fracture in fish; the fractures observed occurred under normal farming conditions and were not induced. The results show that cod have a functional fracture healing mechanism in their neural and haemal spines. The findings are discussed in relation to fish hyperostosis. [ABSTRACT FROM AUTHOR]

Abstract: In vitro cell culture methods are crucial for the isolation, purification and mass propagation of intracellular pathogens of aquatic organisms. Cell culture infection models can yield insights into infection mechanisms, aid in developing methods for disease mitigation and prevention, and inform commercial‐scale cultivation approaches. This study details the establishment of a larval cell line (GML‐5) from the Atlantic cod (Gadus morhua) and its use in the study of microsporidia. GML‐5 has survived over 100 passages in 8 years of culture. The line remains active and viable between 8 and 21°C in Leibovitz‐15 (L‐15) media with 10% foetal bovine serum and exhibits a myofibroblast phenotype as indicated by immuno‐positive results for vimentin, α‐smooth muscle actin, collagen I and S‐100 proteins, while being desmin‐negative. GML‐5 supports the infection and development of two microsporidian parasites, an opportunistic generalist (Anncaliia algerae) and cod‐specific Loma morhua. Using GML‐5, spore germination and proliferation of L. morhua was found to require exposure to basic pH and cool incubation temperatures (8°C), in contrast to A. algerae, which required no cultural modifications. Loma morhua‐associated xenoma‐like structures were observed 2 weeks postexposure. This in vitro infection model may serve as a valuable tool for cod parasitology and aquaculture research. [ABSTRACT FROM AUTHOR]

Selected biomarkers of health were examined in 50 post-spawning cod Gadus morhua collected in November 2015 from the southern Baltic. The biomarkers included condition factor ( CF), macroscopic lesions, histopathology of spleen, liver and gonads, and morphometry of follicular atresia and hepatic and splenic melanomacrophage cells ( MMC). All fish appeared in good body condition. One fish had a dermal ulcer, and in seven, macroscopic nematodes were noted within body cavity. Microscopic lesions in the liver included biliary myxozoanosis, microsporidial and necrocentric granulomas, parasitic hepatitis, multifocal necrosis, foci of cellular alterations, spongiosis, peliosis and cytoplasmic fibrillar inclusions. The spleen and gonads had microsporidial and/or necrocentric granulomas. Some of the biomarkers showed differences as compared to spawning cod collected in May from the same location in 2012, most importantly values an order of magnitude lower for splenic MMC in post-spawning fish. In post-spawning fish, there were statistically significant correlations between MMC, CF, follicular atresia, parasitic hepatitis and microsporidiosis. This is the first comparison of biomarkers of health in post-spawning and spawning Baltic cod. Future studies need to examine the relationships of biomarkers to levels of pollutants in the environment and in tissues of cod. [ABSTRACT FROM AUTHOR]

Capture-based aquaculture ( CBA) of Atlantic cod ( Gadus morhua) has become increasingly important in recent years, and increased attention is being paid to animal welfare issues linked to these activities. Earlier studies showed that some cod develop secondary exophthalmia in captivity. This study investigated the development of secondary exophthalmia in two groups of wild-caught cod, one of which was exposed to rapid decompression causing acute barotrauma (treatment group) while the other was not (control group). Photographs and radiographs before and up to 33 days after barotrauma revealed a significant increase in overall eye protrusion caused by an accumulation of gas in the orbita in the treatment group, first observed on day 9 after decompression, while no protrusions were observed in the control group. Barotrauma was thus identified as an important trigger for the development of secondary uni- or bilateral exophthalmia of wild-caught cod. Two underlying mechanisms are suggested, where the more likely is residual swim bladder gas taking the route of least resistance, while the less likely is the exsolution of gas from the blood. Our results have implications for a wide range of contexts in which cod are rapidly brought to the surface from great depth. [ABSTRACT FROM AUTHOR]

The microsporidian Loma morhua infects Atlantic cod ( Gadus morhua) in the wild and in culture and results in the formation of xenomas within the gill filaments, heart and spleen. Given the importance of the two former organs to metabolic capacity and thermal tolerance, the cardiorespiratory performance of cod with a naturally acquired infection of Loma was measured during an acute temperature increase (2 °C h−1) from 10 °C to the fish's critical thermal maximum ( CTMax). In addition, oxygen consumption and swimming performance were measured during two successive critical swimming speed ( Ucrit) tests at 10 °C. While Loma infection had a negative impact on cod cardiac function at warm temperatures, and on metabolic capacity in both the CTMax and Ucrit tests (i.e. a reduction of 30-40%), it appears that the Atlantic cod can largely compensate for these Loma-induced cardiorespiratory limitations. For example, (i) CTMax (21.0 ± 0.3 °C) and Ucrit (~1.75 BL s−1) were very comparable to those reported in previous studies using uninfected fish from the same founder population; and (ii) our data suggest that tissue oxygen extraction, and potentially the capacity for anaerobic metabolism, is enhanced in fish infected with this microsporidian. [ABSTRACT FROM AUTHOR]

The article explores the epidemic spread of francisellosis disease, a systemic granulomatous inflammatory disease among Celtic Sea Atlantic cod in the North-East Atlantic region. An overview of commercial fishing of Celtic Sea Atlantic cod fishes in the late 1990s is noted. The Norwegian government has conducted funded projects to breed wild-caught cod broodstock fishes. It also highlights a research study for a vaccine development for treating francisellosis disease among Atlantic cod fishes.

A disease outbreak in farmed Atlantic cod caused by Yersinia ruckeri is reported. Mortality started following vaccination of cod reared in two tanks (A and B). The accumulated mortality reached 1.9% in A and 4.8% in B in the following 30 days when treatment with oxytetracycline was applied. Biochemical and molecular analysis of Y. ruckeri isolates from the cod and other fish species from fresh and marine waters in Iceland revealed a high salinity-tolerant subgroup of Y. ruckeri serotype O1. Infected fish showed clinical signs comparable with those of Y. ruckeri -infected salmonids, with the exception of granuloma formations in infected cod tissues, which is a known response of cod to bacterial infections. Immunohistological examination showed Y. ruckeri antigens in the core of granulomas and the involvement of immune parameters that indicates a strong association between complement and lysozyme killing of bacteria. Experimental infection of cod with a cod isolate induced disease, and the calculated LD50 was 1.7 × 104 CFU per fish. The results suggest that yersiniosis can be spread between populations of freshwater and marine fish. Treatment of infected cod with antibiotic did not eliminate the infection, which can be explained by the immune response of cod producing prolonged granulomatous infection. [ABSTRACT FROM AUTHOR]

Piscine mycobacteriosis causes losses in a number of fish species both in the wild and in aquaculture worldwide. Mycobacterium salmoniphilum infections have on several occasions been reported in farmed Atlantic salmon, Salmo salar L. The present study tested and confirmed the susceptibility of Atlantic cod, Gadus morhua L., an important yet relatively novel aquaculture species, to infection with M. salmoniphilum. Atlantic cod injected intraperitoneally with a suspension of this bacterium were maintained together with cohabitant (COH) fish in a flow-through marine water system at 10-11 °C. The fish were supervised daily and samples taken at 2, 7, 14, 23, 34 and 53 weeks post-infection and examined pathologically, bacteriologically and using molecular biology. Injected mycobacteria were re-isolated in high concentrations from both injected and COH fish groups. Death attributable to mycobacterial infection was observed in both injected (47%) and COH (28%) fish groups. Extensive development of granuloma in visceral organs, mainly the mesenteries, spleen, kidney and liver (lesser extent) and at later stages of the infection in heart tissues and gills, was observed in both injected and COH fish. Granulomas underwent a temporal progression of distinct morphological stages, culminating in well-circumscribed lesions surrounded by normal or healing tissue. Acid-fast bacilli were detected in both granulomas and non-granulomatous tissues. This study confirms that Atlantic cod is highly susceptible to M. salmoniphilum infection and that this bacterial species may be a threat to cod both in the wild and in the aquaculture. [ABSTRACT FROM AUTHOR]

Serious infectious diseases, accompanied by macrophage-dominated chronic inflammation, are common in farmed Atlantic cod. To increase knowledge relating to morphological aspects of such inflammatory responses, cod were challenged with Francisella noatunensis, an important bacterial pathogen of this fish species. Tissue and cell dynamics in the spleen were examined sequentially over 60 days. Small clusters of mainly macrophage-like cells (MLCs) staining for non-specific esterase and acid phosphatase developed with time. These foci were transiently infiltrated by pleomorphic proliferating cells of unknown nature and by granulocyte-like cells (GCLCs) staining for peroxidase and lysozyme. The latter cell type, which appeared to be resident in the red pulp of control fish, migrated into the inflammatory foci of infected fish. Cells expressing genes encoding IFN-γ and IL-8 increased in number during the study period. Bacteria were detected only in the MLCs and their number increased despite the extensive inflammation. Our results demonstrate an intimate spatial relationship in inflammatory foci between at least three cell types. The presence of GCLCs, together with MLCs, suggests pyogranulomatous inflammation as a more appropriate descriptive term than granulomatous inflammation. [ABSTRACT FROM AUTHOR]

The duration of efficacy of emamectin benzoate in the control of Caligus curtus infestations in Atlantic cod, Gadus morhua L., was studied following an administration of 50 μg kg for seven consecutive days. No lice were found on medicated fish when challenged 1 week (challenge 1) or 5 weeks (challenge 2) following termination of medication, whereas the mean abundance of lice among the unmedicated fish was 17.9 and 19.3 lice per fish in challenge 1 and 2, respectively. Muscle concentrations of 19.5 ± 8.2 ng g and 3.4 ± 0.9 ng g, respectively, and skin concentrations of 23.1 ± 10.8 and 4.2 ± 1.0 ng g, respectively, were found 27 and 55 days following the termination of medication. Tissue concentrations and the duration of efficacy indicate a dosing regime for emamectin in cod, similar to the regime used for Atlantic salmon, Salmo salar L. [ABSTRACT FROM AUTHOR]

A series of recent reports have implicated bacteria from the family Francisellaceae as the cause of disease in farmed and wild fish and shellfish species such as Atlantic cod, Gadus morhua L., tilapia, Oreochromis spp., Atlantic salmon, Salmo salar L., three-line grunt, Parapristipoma trilineatum (Thunberg), ornamental cichlid species, hybrid striped bass Morone chrysops x M. saxatilis and, recently, a shellfish species, the giant abalone, Haliotis gigantea Gmelin. The range of taxa affected will very probably rise as it is likely that there has been considerable under-reporting to date of these disease agents. In common with other Francisella species, their isolation and culture require specialized solid and liquid media containing cysteine and a source of iron. This likely restricted earlier efforts to identify them correctly as the cause of disease in aquatic animals. The most information to date relates to disease in cod, caused by F. noatunensis and tilapia, caused by F. noatunensis subsp. orientalis (also termed F. asiatica), both causing granulomatous inflammatory reactions. Mortalities in both species can be high and, as the disease can likely be transferred via live fish movements, they pose a significant threat to tilapia and cod aquaculture operations. Although the fish-pathogenic Francisella species are classified in the same genus as the human pathogens F. tularensis, causative agent of tularemia, and F. philomiragia, the risk to humans from the fish and shellfish pathogenic Francisella species is considered very low. [ABSTRACT FROM AUTHOR]

Lernaeocera branchialis, a copepod crustacean parasite of gadoids, represents a potential threat to both wild and farmed cod, Gadus morhua. The pathological changes associated with the early stages of experimental infection have previously been reported in detail, and this article describes the lesions associated with later chronic stages of experimental infection. Chronic infection is characterised by extravascular granuloma formation and proliferation of fibrovascular tissue around intact and fragmented, degenerate parasites within both the gill arch and cardiac region. The majority of parasite granulomas are located within connective tissues of the gill arch or pericardium; however, low numbers are present within the wall of large vessels. The intraluminal parasites and thrombi of early stage infection are largely absent in these later lesions. We propose that organisation and incorporation of the parasite thrombus into the vessel wall with subsequent granuloma formation and extrusion into the surrounding connective tissue leads to the elimination of the parasite from the vascular system. Thus, rather than being a negative consequence of infection thrombosis is protective, allowing the host to survive the substantial initial vascular insult. [ABSTRACT FROM AUTHOR]

The article focuses on a study conducted to investigate the outbreak of viral nervous necrosis (VNN) in the farmed Atlantic cod fishes in Norway during 2006. It discusses the genetic factors causing VNN in farmed juvenile and adult marine fish species, and gives an overview of the investigations done by the study on the infected fishes. Also discussed are the disease symptoms found in fishes during the study, and explores its findings on the pathogenesis and etiology of VNN.

Atlantic cod, Gadus morhua, averaging 100 g, were experimentally challenged by intraperitoneal injection of nervous necrosis virus (NNV) originating from Atlantic halibut. Cod tissues, including blood, gill, pectoral fin, barbel, ventricle, atrium, spleen, liver, lateral line (including muscle tissue), eye (retina) and brain, were sampled at day 25 and 130 and investigated by real-time RT-PCR for the presence of NNV. Relative quantifications at day 130 were calculated using the 2−ΔΔCt method. Immunosuppression by injection of prednisolone-acetate was introduced for a 30-day period, and tissue sampled at day 180 and relative quantification estimated. No mortality or clinical signs of disease were observed in the challenged group. The challenge resulted in detection of NNV in blood, spleen, kidney, liver, heart atrium and heart ventricle at day 25, and by the end of the experiment NNV showed a clear increase in brain and retina, suggesting these to be the primary tissues for viral replication. There was no increase in the relative amount of NNV in blood, atrium, ventricle, spleen, liver and kidney. Corticosteroid implants resulted in a weak increase in virus RNA in spleen, kidney, liver and brain. These findings suggest that Atlantic cod is susceptible to infection with NNV from halibut. The observed tissue tropism patterns suggest an initial viraemic phase, followed by neurotrophy. Head-kidney is the best tissue identified for possible NNV detection by non-lethal biopsy, but detection was not possible in all injected fish. [ABSTRACT FROM AUTHOR]

Viral nervous necrosis (VNN) caused by betanodavirus affects many species of farmed marine fish, in particular juveniles. Apparently healthy, normally feeding, adult farmed Atlantic cod, Gadus morhua, were sampled in a farm 14 months after an outbreak of VNN with clinical signs. Following necropsy, brain and eye tissues were examined by histology, immunohistochemistry and polymerase chain reaction (PCR). Nodavirus-provoked cell death and inflammation was detected in eye and brain, particularly in the retina and cerebellum and differed from that previously described in Atlantic cod during clinical stages of VNN. Virus was detected both by PCR and immunohistochemistry. This is, to the best of our knowledge, the first description of pathological changes associated with chronic subclinical nodavirus infection in Atlantic cod. Our observations suggest that severe infection and pathological changes may go undetected if investigations are restricted to clinical examination and macroscopic evaluation at necropsy. [ABSTRACT FROM AUTHOR]

Intraperitoneal (IP) injection, cohabitation and immersion routes of infection were used to determine if Atlantic cod, Gadus morhua (L.), of 1 and 3 g are susceptible to infectious pancreatic necrosis (IPN). Mortalities of cod injected IP were significantly higher when challenged with infectious pancreatic necrosis virus (IPNV) than with phosphate buffered saline. This is the first report of Atlantic cod mortalities caused by IPNV. Fish challenged by cohabitation had significantly higher mortalities than the controls, but mortalities of Atlantic cod challenged with IPNV by immersion were not significantly different from controls. Titres of IPNV in the tissues of infected fish were sometimes very high (range 102–1010 infectious units per gram of tissue) suggesting virus replication and titres of fish that died were generally higher than those of fish which survived. However, the relatively low mortality rates when challenged by cohabitation and immersion (20% and 17%, respectively), compared to the IP injection challenge (100%) suggest that 1 and 3 g cod have low susceptibility to IPN when challenged by more natural routes. These data strongly suggest that the cause of death of experimentally challenged cod was IPNV and further histological evidence for this came from 1 g cod challenged IP with IPNV in which the pancreas showed severe necrosis and heavy immunostaining for IPNV coincidentally with the peak of mortalities. [ABSTRACT FROM AUTHOR]

Suppression subtractive hybridization was used to investigate the response of turbot, Psetta maxima (L.), to Vibrio harveyi, by using a cDNA library constructed from artificially infected turbot kidney and spleen mRNA. Forty-nine expressed sequence tags were obtained. Several immune system genes were identified, including a major histocompatibility complex (MHC) class Ia gene and a heat shock protein 70 gene. Some signalling molecules were also present in the cDNA libraries, including src-family tyrosine kinase SCK, sgk-1 serine-threonine protein kinase and amyloid precursor-like protein 2. The full length of MHC class Ia cDNA was cloned from turbot cDNA by rapid amplification of cDNA ends polymerase chain reaction. The nucleotide sequence of turbot MHC class Ia has been submitted to GenBank with accession number . The turbot MHC class Ia cDNA has an open reading frame encoding 354 amino acids, and the deduced amino acid sequence of turbot MHC class Ia has 68%, 54%, 51%, 52%, 57%, 33%, 29% and 29% identities to those of olive flounder, medaka, rainbow trout, Atlantic cod, tiger puffer, chicken, mouse and human, respectively. Quantitative reverse transcriptase-PCR was performed for the MHC class Ia gene, and it was revealed that the expression level of the MHC class Ia gene in V. harveyi-challenged turbot increased to fourfold that of the controls. [ABSTRACT FROM AUTHOR]

Francisellosis, caused by the bacterium Francisella piscicida, has become one of the most serious diseases in Atlantic cod production in Norway. The major aim of this study was to determine the distribution of F. piscicida in farmed and wild fish in areas with cod farming along the Norwegian coast, and its occurrence in cod from areas without cod farming. Two real-time PCR assays, targeting the 16S rRNA gene and the FopA gene of F. piscicida, were developed since sensitive and specific diagnostic tools are required for detecting asymptomatic carriers of the bacterium. A total of 422 wild cod from 13 sampling areas and 955 farmed cod from 10 areas along the coast of Norway were examined. Using the real-time polymerase chain reaction (PCR) assays, F. piscicida was detected in wild populations of cod from all counties examined south of Sogn og Fjordane in southern Norway (overall prevalence 13%, n = 221). Wild cod north of Sogn og Fjordane were negative for the bacterium ( n = 201). Farmed cod from most parts of Norway were F. piscicida positive. The apparent absence of the bacterium in wild populations of cod in the northern parts of Norway and its widespread occurrence in wild cod from southern parts of Norway is believed to relate to differences in seawater temperatures. [ABSTRACT FROM AUTHOR]

Previous work in our group has identified the scavenger endothelial cells (SECs) of heart endocardium in cod, Gadus morhua L., as the major site for elimination of both physiological and foreign macromolecular waste from the circulation. The present study was undertaken to establish the role of cod SECs in the clearance of virus. We focused on infectious pancreatic necrosis virus (IPNV) as it is a well-known virus with a broad host range, and causes significant economic losses in the salmon industry. Our results showed that cod SEC cultures infected by the IPNV produce high titres of new virus. Ligand-receptor inhibition experiments suggested that the virus did not enter the cells through any of the major endocytosis receptors of cod SECs. Yet, the infection lowered the capacity of the cells to endocytose ligands via the scavenger receptor. Inhibitors of receptor recycling and vesicle acidification did not affect virus infectivity. The finding that SEC cultures prepared from 25% of the cod produced high titres of IPNV without being infected in the laboratory, suggests that SECs of cod may serve as reservoirs for IPNV in persistently infected cod. [ABSTRACT FROM AUTHOR]

Lernaeocera branchialis is a penellid copepod, the adults of which are commonly found on gadoids in the North Atlantic and North Sea. L. branchialis has a severe negative impact on wild gadoids and is a potentially serious pathogen of farmed cod, Gadus morhua. This paper describes an experimental infection by cohabiting the intermediate host, the flounder, Platichthys flesus, heavily infected with juvenile stages of L. branchialis, with hatchery-reared cod in order to study the pathology of the early stages of infection of the final host. Early stages of L. branchialis induce extensive local gill hyperplasia, large intravascular thrombus formation and a moderate cellular immune response in the cardiac and branchial tissues of G. morhua. The parasite appears to migrate within the lumen of the afferent branchial artery, ventral aorta and in turn, that of the bulbus arteriosus. These findings are consistent with the presence of a haematophagous, voluminous and rapidly invasive parasite. [ABSTRACT FROM AUTHOR]

This study was performed to determine the efficacy of orally administered florfenicol in the treatment of experimentally induced vibriosis ( Listonella anguillarum) in cod, Gadus morhua. The L. anguillarum strain HI-610 was used. This strain has a minimal inhibitory concentration value of 0.5 mg L−1 against florfenicol. Fifteen groups of 40 fish each were challenged by bath with 1.7 × 105 CFU mL−1 for 1 h. Three days following challenge, medication with florfenicol was introduced in 12 of the groups. The dosages used were 10 mg kg−1 day−1 for 10 consecutive days in marine or salmonid pellets, 10 mg kg−1 day−1 for five consecutive days in marine pellets or administered at days 1, 2, 4, 6 and 8 following initiation of treatment. Among challenged unmedicated fish mortality started at day 3 post-challenge reaching a final cumulative mortality of 77% at day 15. The experiment was terminated at day 26. In the medicated groups, the majority of deaths occurred from days 3–7 post-challenge reaching final cumulative mortalities of 31% and 52%, respectively, for the fish given marine and salmonid pellets for 10 consecutive days. The fish treated with medicated marine pellets for five consecutive days and at days 1, 2, 4, 6 and 8 (sequential feeding) following initiation of treatment had cumulative mortalities of 52% and 38%, respectively. Survival of medicated fish in all groups was significantly ( P < 0.005) greater than survival of challenged unmedicated fish. Furthermore, a significant difference ( P < 0.001) in survival was found between fish treated for 10 consecutive days using marine pellets and the groups using marine pellets for five consecutive days and salmonid pellets for 10 consecutive days. Twenty four hours following last medication, six fish had mean plasma concentrations of 3.3 ± 1.7 and 3.5 ± 2.8 μg mL−1, respectively, in fish treated for 10 consecutive days using marine and salmonid pellets. Corresponding values for fish treated for five consecutive days and by sequential feeding were 2.2 ± 2.3 and 1.7 ± 0.7 μg mL−1, respectively. [ABSTRACT FROM AUTHOR]

In this study experimental challenges with Moritella viscosa, the causative agent of winter ulcers in salmonids, were performed on juvenile Atlantic cod and Atlantic halibut. The challenges involved both intramuscular (i.m.) and intraperitoneal (i.p.) injections and bath with a strain originally isolated from Atlantic salmon. Cod was found to be significantly more sensitive than halibut to the infection. Both fish species were found to be more sensitive to i.m. than i.p. challenges. Both challenges induced a systemic disease in cod and halibut, but only cod was infected with an experimental bath challenge. Pathognomonic signs were found to be comparable with those described in M. viscosa-infected salmon and turbot. The main distinguishing pathological sign was that the cod showed host response to M. viscosa infection resulting in granuloma formation in infected tissues, which is a known response of cod to a infection with another Gram-negative bacterium, Aeromonas salmonicida. Re-isolation of M. viscosa from kidneys of cod and halibut with clear disease signs was problematic and optimization of isolation measures is needed. The results of this study indicate that M. viscosa infection may be a risk factor in cod farming, but that halibut is more resistant. [ABSTRACT FROM AUTHOR]

Juvenile Atlantic cod (10 g) were infected with infectious pancreatic necrosis virus (IPNV) by intraperitoneal injection and cohabitation. Fish showed no signs of disease but IPNV could be re-isolated from kidney tissue for up to 12 weeks. On weeks 2, 5, 8, 10, 11 and 12 following infection, kidney leucocytes were fractionated on Percoll gradients, and cells separated into plastic adherent and non-adherent cell populations after overnight incubation. IPNV was detectable in lysates of both cell populations and in supernatants by culture in CHSE-214 cells. Wells containing 105−106 macrophages had an IPNV TCID50 of about 103/well and in serially diluted macrophages the minimum number of cells required to detect virus ranged from 101 to 104. These data indicate that about one in 104 macrophages were infected and the mean number of virus/infected cell was about 10. Replication of IPNV in the macrophages was low as the titre of the virus in macrophage lysates did not increase between days 1 and 3 of culturing the macrophages, but virus was released into the supernatant over this time. [ABSTRACT FROM AUTHOR]

The article presents a study on a systemic granulomatous inflammatory disease in Atlantic cod associated with the presence of a gram-negative and intracellular bacterium from the Francisella group. It observed the fish population which was composed of mature cods in a closed natural seawater basin and was given commercial dry feed. The study was carried out about five months and obtain a result of 40 percent mortality level. The result suggested that the larger fish were the ones affected.

The sea louse Caligus elongatus utilizes a range of marine fish species as hosts, and it has been suggested that fish farms are infected with adult C. elongatus from wild fish hosts. We assessed experimentally whether dislodged lice return to their original host species. Adult lice from wild lumpfish and saithe were presented to lumpfish, sea trout, Atlantic cod, saithe and European plaice. All fish species became infected. Lumpfish and cod were strongly preferred, followed by saithe, trout and plaice. Lice from wild saithe showed a preference for saithe and lumpfish, followed by cod, sea trout and plaice. The mtCO1 gene was used to determine the genotypes of the lice. Lice from lumpfish were genotype 1. Lice from saithe were mainly genotype 2. The two genotypes of C. elongatus differed slightly in their host preferences: lice from saithe were less discriminating. The data support the hypothesis that adult C. elongatus may transfer between different host species. Cod is an attractive host for lice from both lumpfish and saithe, which suggests that C. elongatus may become a serious pest of farmed cod. [ABSTRACT FROM AUTHOR]

Viral haemorrhagic septicaemia (VHS) is a well-characterized disease of rainbow trout, Oncorhynchus mykiss, which has also caused economic losses in marine turbot farms in the British Isles. We have previously demonstrated that turbot, Scophthalmus maximus, are susceptible to isolates of viral haemorrhagic septicaemia virus (VHSV) that are endemic in the marine environment, highlighting a potential risk to marine aquaculture. Given the increasing interest in the intensive rearing of additional aquaculture species such as Atlantic cod, Gadus morhua, and Atlantic halibut, Hippoglossus hippoglossus, this study aimed at investigating the susceptibility of these species to VHSV. Both species were found to be largely resistant to VHS following immersion challenge with a selection of 18 isolates, representing the known marine VHSV genotypes. Only one and two VHSV-associated mortalities occurred out of a total of 1710 and 1254 halibut and cod, respectively. These findings suggest that there is a low direct risk to the development of commercial cod and halibut aquaculture from the existing endemic reservoir of VHSV. This study, coupled to field observations has, however, highlighted the fact that both species can become infected with VHSV. The known adaptability of RNA viruses, together with the selection pressures associated with intensive aquaculture would thus advocate a cautious approach to VHSV surveillance within these emerging industries. [ABSTRACT FROM AUTHOR]

Examines the pseudomonas anguilliseptica infection in farmed cod, Gadus morhua L. Isolation of bacteria in large numbers and in pure culture; Similarity of the disease to the cephalic form of Flavobacterium psychrophilum infection in young rainbow trout; Presence of blindness due to apparent cataract in some fish.

The article focuses on disease outbreaks and mass mortality in cultured Atlantic cod Gadus morhua L., associated with trichodina murmanica. The present study was conducted to ascertain the prevalence of the parasite infecting Atlantic cod in a coastal embayment of Newfoundland. Additionally, an experimental study investigated the effect of the parasite on morbidity and mortality in cultured cod. Outbreaks and mass mortality associated with the parasitic infection are also reported herein. A survey was conducted to ascertain the prevalence of trichodinid infections in wild juvenile and adult Atlantic cod.

Abstract The pharmacokinetic properties of the antibacterial agent oxolinic acid and vetoquinol, the carbitol ester of oxolinic acid, were studied after intravenous (i.v.) and oral (p.o.) administration to 100–150 g cod, Gadus morhua L., held in sea water at 8 °C. Following i.v. injection, the plasma drug concentration-time profile showed two distinct phases. The distribution half-life (t 1/2 α ) was estimated at 1.3 h, the elimination half-life (t 1/2 β ) as 84 h and the total body clearance (ClT ) as 0.047 L kg-1 h-1 . The volume of distribution at steady state, V d(ss) was calculated to be 5.5 L kg-1 , indicating good tissue penetration of oxolinic acid in cod. Following p.o. administration of oxolinic acid or vetoquinol, the peak plasma concentrations (C max ) of oxolinic acid and the time to peak plasma concentrations (T max ) were estimated to be 1.2 and 2.5 μg mL-1 , and 24 and 12 h, respectively. The bioavailabilities of oxolinic acid following p.o. administration of oxolinic acid and vetoquinol were calculated to be 55 and 72%, respectively. The in vitro minimum inhibitory concentration (MIC) values of oxolinic acid against three strains of Vibrio anguillarum isolated from diseased cod were 0.016 μg mL-1 (HI-610), 0.250 μg mL-1 (HI-618) and 0.250 μg mL-1 (HI-A21). Based on a MIC value of 0.016 μg mL-1 a single p.o. administration of 25 mg kg-1 of oxolinic acid maintains plasma levels in excess of 0.064 μg mL-1 , corresponding to four times the MIC-value, for approximately 12 days. The analogous value for a single p.o. dose of 25 mg kg-1 of oxolinic acid administered as vetoquinol was 13 days. [ABSTRACT FROM AUTHOR]

Abstract Cod, Gadus morhua L., of wild origin, were reared at different temperatures for 12 months. During this period, moribund and newly dead fish were examined and samples collected for bacteriology and histopathology. Atypical Aeromonas salmonicida was isolated from 10 individuals reared at or above 7 °C. The isolates were homogeneous with respect to biochemical and antibiogram characters and similar to the ssp. achromogenes National Collection of Industrial and Marine Bacteria, UK, type strain 1110 and reference strains that have been isolated from salmonids and haddock in Iceland. Histopathological analysis of the naturally infected cod showed typical ulceration associated with atypical A. salmonicida infection and also widespread granulomatous formations. One-year-old cod of farmed origin, kept at 9 °C, received intraperitoneal or intramuscular injection with different doses of atypical A. salmonicida , isolated from the above wild cod. Mortalities were monitored for 28 days and the LD50 calculated. The route of bacterial injection influenced the mortality rate and LD50 value and affected, to some extent, the pathological changes observed and humoral immune parameters. Pathological changes, including haemorrhage, early stages of granuloma formation and necrotic changes, were seen in several organs. Infection appeared to induce non-specific antibody activity against trinitrophenyl (TNP)-haptenated protein and may have activated the complement system. Specific antibody response against atypical A. salmonicida was not detected. [ABSTRACT FROM AUTHOR]

Αbstract Τhe uptake and distribution of lipopolysaccharide (LPS), isolated from Aeromonas salmonicida, was investigated in Atlantic cod, Gadus morhua L., turbot, Scophthalmus maximus L., and Atlantic halibut, Hippoglossus hippoglossus L. LPS was radiolabelled by bromine oxidation and subsequent sodium borotritide reduction (3H-LPS), and fluorescence-labelled by introducing a fluorescein isothiocyanate derivative (FITC-LPS). After intravenous and intraperitoneal injections in cod, high amounts of radioactive LPS (3H-LPS) were present in heart, spleen and kidney throughout the experimental period (1–168 h). After peroral administration, a high amount of 3H-LPS was observed in intestinal tissues, whereas internal organs and tissues contained considerably lower amounts. Following intravenous administration of 3H-LPS in turbot, high contents of radioactivity were revealed in spleen, liver and kidney, whereas the content in heart was lower than in blood at the sampling times (1–24 h). The same pattern was observed after intraperitoneal administration. The spleen and liver contained high amounts of radioactivity when the turbots were intubated perorally with 3H-LPS. The spleen, kidney and heart were the main scavenging organs following intravenous administration of 3H-LPS in Atlantic halibut. A minor amount of radioactivity was present in the liver. The same pattern emerged after intraperitoneal injection in halibut. As observed for turbot, the spleen was the main accumulation site for 3H-LPS following peroral administration. Fluorescence microscopy of sections of organs and tissues from cod, intravenously and intraperitoneally injected with FITC-LPS, revealed that endocardial cells of both atrium and ventricle contained large amounts of the fluorochrome, whereas in turbot and halibut only atrial endothelial cells accumulated the substance. In all species, macrophages... [ABSTRACT FROM AUTHOR]

Abstract The cultivation of Atlantic cod, Gadus morhua L., head kidney macrophages was optimal at 4–6 °C. The viability of cells in culture was examined by the trypan blue exclusion test 2, 5 and 7 days after seeding. Simultaneously, the number of adherent cells at the various times was checked. The morphology of the cells was also evaluated during the cultivation period. Enhanced respiratory burst activities were demonstrated in macrophages after stimulation with known immunostimulants like lipopolysaccharide, tuftsin and an acid peptide fraction previously shown to stimulate Atlantic salmon leucocytes efficiently. Generally, the Atlantic cod macrophages seemed to respond to a lesser extent compared with macrophages obtained from both mammalian and other fish species. [ABSTRACT FROM AUTHOR]

Head kidney macrophages from Atlantic cod, Gadus morhua L., were isolated by density sedimentation and maintained under serum-free conditions for up to one week. The cells adhered and spread well on glass and plastic, were highly phagocytic, and had typical macrophage morphology as shown by phase contrast and scanning and transmission electron microscopy. Histochemical studies with the light microscope showed that the macrophages were acid phosphatase and non-specific esterase positive, and alkaline phosphatase and peroxidase negative. Compared with unstimulated control cells, LPS-treated cells showed enhanced superoxide anion formation, as measured by the reduction of nitroblue tetrazolium, and increased levels of acid phosphatase activity. [ABSTRACT FROM AUTHOR]

The tissue distribution of ³H- and FITC-laminaran in Atlantic cod, Gadus morhua L., was investigated after intravenous administration. Liquid scintillation counting and whole-body autoradiography revealed a substantial accumulation of ³H-labelled laminaran in the heart throughout the experimental period (1 h to 12 days). High amounts of the immunomodulator were also present in the spleen, anterior kidney and posterior kidney during the study. Renal excretion and intestinal exsorption were the main elimination pathways. Fluorescence microscopic examination revealed accumulation of FITC-labelled laminaran in macrophages in the kidney and ellipsoid sheath cells (macrophages and reticular cells) in the spleen. Furthermore, endothelial entrapment in the heart was pronounced. Endothelial cells in the kidney also contained the FITC-labelled immunomodulator. Immunohistochemical analysis, using anti-β(l,3)-D-glucopyranose antibody, also showed endothelial uptake of laminaran in the heart. The present investigation shows that laminaran accumulates and is retained in immunologically relevant cells in the Atlantic cod. [ABSTRACT FROM AUTHOR]

The article focuses on atypical aeromonas salmonicida infection in Atlantic cod, gadus morhua L. In this study skin lesions, kidney and intestine were cultured on tryptic soy agar (Difco) with and without NaCI supplement to 2 %, as well as on blood agar. Thirty freshly caught cod from Terence Bay were sampled for bacteriology in an attempt to establish the source of the infection. The cod injected with A. saimonicida and sampled bacteriologically after death yielded A. salmonicida from all sites except the intestine, which gave a heavy growth of vibrio anguillarum.

The histopathology of an atypical Aeromonas salmonicida found in Atlantic cod, Gadus morhua L., is described. Unlike members of the Salmonidae, the cod showed a well-developed host reaction to A. salmonicida involving encystment of the bacteria. When Atlantic salmon, Salmo salar L., were given an intra-muscular injection with suspensions of cultures of this strain of A. salmonicida no cellular host reaction was observed. When cod were given a similar injection the bacteria showed degenerative changes, leucocytes accumulated, and cyst formation was seen in the spleen and kidney. Since cod can be infected by this organism the possibility exists that they could act as carriers, a source of infection for salmonids in saltwater cage culture or in the wild. [ABSTRACT FROM AUTHOR]

The article focuses on a study related to pseudobranchial tumors in Atlantic cod, Gadus morhua L. Since 1975 cod catches aboard Norwegian research vessels in the Barents sea have been occasionally examined for pseudobranchial tumors. Such tumors were sometimes found and were usually large enough to cause the opercula to be forced outwards. A number of surveys were carried out on fishes in the Barents Sea. In the first survey, five of the six tumor-bearing fish had bilateral tumors. The catches of cod in surveys were rather small especially in the western part of the Barents Sea.

A microsporidium, forming xenoparasitic complexes (xenomas) of the cell-hypertrophy tumour type, was found in the gills of the Atlantic cod Gadus morhua L. and studied with the electron microscope. It seemed to be similar to Nosema branchiale Nemeczek, 1911, in the haddock Melanogrammus aeglefinus (L.) except in size of spore. The xenoma (cyst) was basically like the Glugea cyst and the parasite had some other characters in common with Glugea; it was apansporoblastic, unikaryotic, disporoblastic and underwent partial development in parasitophorous vacuoles. It differed from Glugea in lacking plasmodial stages, producing usually 1 or 2 spores (rather than 16) in a vacuole, showing no distinct tendency for different stages to occur in different zones of the cyst and having tubules in the parasitophorous vacuoles. The name Loma morhua n. g., n. sp. (type) was proposed and the genus assigned to the family Glugeidae Thélohan, 1892. The parasite of haddock gill was transferred to the new genus, becoming L. branchialis (Nemeczek, 1911) n. comb. [ABSTRACT FROM AUTHOR]

The article focuses on the presence of Francisella sp. in Atlantic salmons in Chile. Francisella sp. has been linked to granulomatous disease in Atlantic salmon and to the death of various fish species including tilapia, three-line grunt, and hybrid striped bass. Various queries have been raised as regard the existence of the bacteria in Atlantic salmons in fresh and seawater worldwide.