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Find video protocols related to scientific articles indexed in Pubmed.
Characterization of serum amyloid A (SAA) in rainbow trout using a new monoclonal antibody.
Fish Shellfish Immunol.
PUBLISHED: 08-19-2014
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Serum amyloid A (SAA) is an integral part of the innate immune response in mammals and considered to be important during the acute phase response. The present study was undertaken to elucidate the role of SAA protein in the innate immune response of rainbow trout. A monoclonal antibody raised against a recombinant peptide of rainbow trout SAA was characterized using Western blot, dot blot, ELISA and immunohistochemistry. SAA association with high density lipoprotein (HDL) complicated band identification in Western blot, but delipidization of the SAA-HDL isolate highly increased the quality of reaction in the western blot. Rainbow trout fry (87 days post hatch) infected with Yersinia ruckeri showed a significant up-regulation of the SAA gene at 72 h post infection with an increase until 96 h post infection. Non-significant up-regulations were seen at earlier time points i.e. 4 and 24 h. The expression pattern of SAA significantly correlated to the immunohistochemical analysis of the infected fry. A weak staining was seen in liver tissue at 4 h post infection which increased in intensity during the course of infection i.e. 24, 72 and 96 h post infection.
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Occurrence of zoonotic nematodes Pseudoterranova decipiens, Contracaecum osculatum and Anisakis simplex in cod (Gadus morhua) from the Baltic Sea.
Vet. Parasitol.
PUBLISHED: 04-30-2014
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Baltic cod Gadus morhua (a total of total 224 specimens) captured east of the island of Bornholm in the southern Baltic Sea were subjected to a parasitological investigation between March 2013 and April 2014. Full artificial digestion of fillets from 188 cod and additional investigation of livers from 36 cod were performed. Cod or seal worm Pseudoterranova decipiens was recorded in musculature (prevalences up to 55% and intensities up to 56 worms per fish) associated with a negative correlation between worm intensity and condition factor. Liver worm Contracaecum osculatum (100% prevalence with intensities up to 320 worms per fish) in liver tissue were recorded but only a slight negative correlation between intensity and condition factor was noted. Seals act as final host for both worm species and the increased occurrence during recent years is associated with the increasing grey seal population in the area. Infection with Anisakis simplex (the herring or whale worm) in Baltic cod was found at a low level corresponding to previous studies.
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Increased Contracaecum osculatum infection in baltic cod (Gadus morhua) livers (1982-2012) associated with increasing grey seal (Halichoerus gryphus) populations.
J. Wildl. Dis.
PUBLISHED: 04-29-2014
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Grey seals (Halichoerus gryphus), the main final host of the gastric parasitic nematode Contracaecum osculatum in the Baltic, have recently recolonized the southwestern Baltic Sea. This colonization could lead to an increase in prevalence and intensity of third-stage larvae of C. osculatum in livers of Baltic cod (Gadus morhua), which serve as transport host for this helminth. We performed a parasitologic study of cod in spring 2012 and compared the results with previously unpublished data from 1982/1983. Additionally, grey seals were counted annually from 2000 to 2011 at three haul-out sites in the southwestern Baltic. Of 97 cod livers examined in the 1982/1983 survey, 22% harbored C. osculatum larvae, whereas 55.1% of the examined cod livers (n=185) were infected in 2012; the mean intensity and mean abundance increased from 4.3 and 0.9 to 20.2 and 11.1, respectively. Molecular identification (PCR) confirmed the identity of the larvae. The grey seal population increased markedly during the 12-yr period. We suggest that the elevated parasitism of cod livers is associated with the successful re-establishment of grey seals in the southwestern Baltic.
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Annual and spatial variability in endo- and ectoparasite infections of North Sea cod (Gadus morhua Linnaeus, 1758) larvae, post-larvae and juveniles.
Acta Parasitol.
PUBLISHED: 03-12-2014
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A parasitological investigation was performed on a total of 5380 Atlantic cod larvae, post-larvae and small juveniles sampled from the North Sea during a period of five years. The copepod Caligus elongatus (Von Nordmann, 1832) and the nematode Hysterothylacium aduncum (Rudolphi, 1802) were found at a relatively high prevalence of infection (4.6% and 5.2%, respectively). The infection by both parasites showed annual and spatial variability. C. elongatus showed a higher prevalence in 1992 compared to the following years, whereas the prevalence of H. aduncum increased from 1992 to 2001.We observed a relation between parasite distribution and parameters such as latitude and water depth. Adult digeneans (Lecithaster gibbosus and Derogenes varicus) and larval cestodes were also found with lower infection rates. Since changes of infection levels coincided with increasing North Sea water temperature in the studied period, it is hypothesized that temperature may affect parasite population levels. However, it is likely that other environmental factors may contribute to the observed variations. Absence of infection intensities higher than one nematode per fish in small larvae and post-larvae suggests that host survival may be affected by a high infection pressure. The relatively high levels of infection in the younger stages of cod, and the annual/spatial variability of these infections should be considered in the understanding of the early life dynamics of the species.
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Import of exotic and zoonotic trematodes (Heterophyidae: Centrocestus sp.) in Xiphophorus maculatus: implications for ornamental fish import control in Europe.
Acta Parasitol.
PUBLISHED: 03-11-2014
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Ornamental fish, Xiphophorus maculatus, were imported from Singapore to Denmark for distribution to local aquarists. Importers observed lethargic and erratic swimming patterns among fish and forwarded a total of 30 fish for pathological examination to a university diagnostic service. All fish were diagnosed infected with encysted Centrocestus sp. metacercariae in gills (prevalence of 100% and mean intensity of 454.5 ± 161.9 parasites per fish). Metacercariae were identified by morphological and molecular methods. Cysts (mean length 163.3 ± 13.7 ?m and mean width 113.3 ± 10.6 ?m) contained a bent metacercaria with an X-shaped excretory bladder. PCR amplification of a rDNA region (5.8S rRNA gene, ITS-2, 28S rRNA gene) and subsequent sequencing confirmed the diagnosis. Metacercariae were found in gill filaments adjacent to the cartilage associated with cartilage hypertrophy, epithelial and mucous cell hyperplasia, clubbing and lamellar fusion. Host cell encapsulation of cysts comprised several layers of leucocytes, chondroblast-like and fibroblast-like cells. The observations raise concerns with regard to veterinary inspection and quarantine procedures. The zoonotic potential of these trematodes and a possible spread of the parasites in natural habitats in Europe should be regarded as a public health issue. So far, several cases of human infections have been reported only in Asia, but the potential intermediate host snail, Melanoides tuberculata, has been recorded in Germany. Accordingly, establishment of the parasite in Europe with climate changes should be considered a risk.
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Adaptive and innate immune molecules in developing rainbow trout, Oncorhynchus mykiss eggs and larvae: expression of genes and occurrence of effector molecules.
Fish Shellfish Immunol.
PUBLISHED: 02-12-2014
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The ontogenetic development of the immune system was studied during the egg phase and the early post-hatch period of rainbow trout. Quantitative real-time PCR (qPCR) was used to assess the timing and degree of expression of 9 important immune relevant genes and EF1-?. Further, immunohistochemical staining using monoclonal antibodies was applied on rainbow trout embryos and larvae in order to localize five different protein molecules (MHCII, CD8, IgM, IgT and SAA) in the developing tissue and immune organs. Maternally transferred transcripts of EF1-? mRNA were detected in the unfertilized egg. Early onset of expression was seen for all immune genes at very low levels. The amount of mRNA slowly increased and peaked around and after hatching. The highest increases were seen for MHCII, C3, C5 and SAA. Immunohistochemistry using five monoclonal antibodies showed positive staining from day 84 post fertilization. Skin, gills, intestine, pseudobranch and thymus showed reactivity for MHCII, thymus for CD8, gill mucus for IgT and pseudobranch and cartilage associated tissue for SAA. The importance of detected factors for early protection of eggs and larvae is discussed.
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Fauna europaea: helminths (animal parasitic).
Biodivers Data J
PUBLISHED: 01-01-2014
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Fauna Europaea provides a public web-service with an index of scientific names (including important synonyms) of all living European land and freshwater animals, their geographical distribution at country level (up to the Urals, excluding the Caucasus region), and some additional information. The Fauna Europaea project covers about 230,000 taxonomic names, including 130,000 accepted species and 14,000 accepted subspecies, which is much more than the originally projected number of 100,000 species. This represents a huge effort by more than 400 contributing specialists throughout Europe and is a unique (standard) reference suitable for many users in science, government, industry, nature conservation and education. Helminths parasitic in animals represent a large assemblage of worms, representing three phyla, with more than 200 families and almost 4,000 species of parasites from all major vertebrate and many invertebrate groups. A general introduction is given for each of the major groups of parasitic worms, i.e. the Acanthocephala, Monogenea, Trematoda (Aspidogastrea and Digenea), Cestoda and Nematoda. Basic information for each group includes its size, host-range, distribution, morphological features, life-cycle, classification, identification and recent key-works. Tabulations include a complete list of families dealt with, the number of species in each and the name of the specialist responsible for data acquisition, a list of additional specialists who helped with particular groups, and a list of higher taxa dealt with down to the family level. A compilation of useful references is appended.
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Early Immune Responses in Rainbow Trout Liver upon Viral Hemorrhagic Septicemia Virus (VHSV) Infection.
PLoS ONE
PUBLISHED: 01-01-2014
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Among the essential metabolic functions of the liver, in mammals, a role as mediator of systemic and local innate immunity has also been reported. Although the presence of an important leukocyte population in mammalian liver is well documented, the characterization of leukocyte populations in the teleost liver has been only scarcely addressed. In the current work, we have confirmed the presence of IgM+, IgD+, IgT+, CD8?+, CD3+ cells, and cells expressing major histocompatibility complex (MHC-II) in rainbow trout (Oncorhynchus mykiss) liver by flow cytometry and/or immunohistochemistry analysis. Additionally, the effect of viral hemorrhagic septicemia virus (VHSV) on the liver immune response was assessed. First, we studied the effect of viral intraperitoneal injection on the transcription of a wide selection of immune genes at days 1, 2 and 5 post-infection. These included a group of leukocyte markers genes, pattern recognition receptors (PRRs), chemokines, chemokine receptor genes, and other genes involved in the early immune response and in acute phase reaction. Our results indicate that T lymphocytes play a key role in the initial response to VHSV in the liver, since CD3, CD8, CD4, perforin, Mx and interferon (IFN) transcription levels were up-regulated in response to VHSV. Consequently, flow cytometry analysis of CD8?+ cells in liver and spleen at day 5 post-infection revealed a decrease in the number of CD8?+ cells in the spleen and an increased population in the liver. No differences were found however in the percentages of B lymphocyte (IgM+ or IgD+) populations. In addition, a strong up-regulation in the transcription levels of several PRRs and chemokines was observed from the second day of infection, indicating an important role of these factors in the response of the liver to viral infections.
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Evolution of Innate Immunity: Clues from Invertebrates via Fish to Mammals.
Front Immunol
PUBLISHED: 01-01-2014
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Host responses against invading pathogens are basic physiological reactions of all living organisms. Since the appearance of the first eukaryotic cells, a series of defense mechanisms have evolved in order to secure cellular integrity, homeostasis, and survival of the host. Invertebrates, ranging from protozoans to metazoans, possess cellular receptors, which bind to foreign elements and differentiate self from non-self. This ability is in multicellular animals associated with presence of phagocytes, bearing different names (amebocytes, hemocytes, coelomocytes) in various groups including animal sponges, worms, cnidarians, mollusks, crustaceans, chelicerates, insects, and echinoderms (sea stars and urchins). Basically, these cells have a macrophage-like appearance and function and the repair and/or fight functions associated with these cells are prominent even at the earliest evolutionary stage. The cells possess pathogen recognition receptors recognizing pathogen-associated molecular patterns, which are well-conserved molecular structures expressed by various pathogens (virus, bacteria, fungi, protozoans, helminths). Scavenger receptors, Toll-like receptors, and Nod-like receptors (NLRs) are prominent representatives within this group of host receptors. Following receptor-ligand binding, signal transduction initiates a complex cascade of cellular reactions, which lead to production of one or more of a wide array of effector molecules. Cytokines take part in this orchestration of responses even in lower invertebrates, which eventually may result in elimination or inactivation of the intruder. Important innate effector molecules are oxygen and nitrogen species, antimicrobial peptides, lectins, fibrinogen-related peptides, leucine rich repeats (LRRs), pentraxins, and complement-related proteins. Echinoderms represent the most developed invertebrates and the bridge leading to the primitive chordates, cephalochordates, and urochordates, in which many autologous genes and functions from their ancestors can be found. They exhibit numerous variants of innate recognition and effector molecules, which allow fast and innate responses toward diverse pathogens despite lack of adaptive responses. The primitive vertebrates (agnathans also termed jawless fish) were the first to supplement innate responses with adaptive elements. Thus hagfish and lampreys use LRRs as variable lymphocyte receptors, whereas higher vertebrates [cartilaginous and bony fishes (jawed fish), amphibians, reptiles, birds, and mammals] developed the major histocompatibility complex, T-cell receptors, and B-cell receptors (immunoglobulins) as additional adaptive weaponry to assist innate responses. Extensive cytokine networks are recognized in fish, but related signal molecules can be traced among invertebrates. The high specificity, antibody maturation, immunological memory, and secondary responses of adaptive immunity were so successful that it allowed higher vertebrates to reduce the number of variants of the innate molecules originating from both invertebrates and lower vertebrates. Nonetheless, vertebrates combine the two arms in an intricate inter-dependent network. Organisms at all developmental stages have, in order to survive, applied available genes and functions of which some may have been lost or may have changed function through evolution. The molecular mechanisms involved in evolution of immune molecules, might apart from simple base substitutions be as diverse as gene duplication, deletions, alternative splicing, gene recombination, domain shuffling, retrotransposition, and gene conversion. Further, variable regulation of gene expression may have played a role.
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Insight from molecular, pathological, and immunohistochemical studies on cellular and humoral mechanisms responsible for vaccine-induced protection of rainbow trout against Yersinia ruckeri.
Clin. Vaccine Immunol.
PUBLISHED: 08-21-2013
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The immunological mechanisms associated with protection of vaccinated rainbow trout, Oncorhynchus mykiss, against enteric redmouth disease (ERM), caused by Yersinia ruckeri, were previously elucidated by the use of gene expression methodology and immunochemical methods. That approach pointed indirectly to both humoral and cellular elements being involved in protection. The present study correlates the level of protection in rainbow trout to cellular reactions in spleen and head kidney and visualizes the processes by applying histopathological, immunohistochemical, and in situ hybridization techniques. It was shown that these cellular reactions, which were more prominent in spleen than in head kidney, were associated with the expression of immune-related genes, suggesting a Th2-like response. Y. ruckeri, as shown by in situ hybridization (ISH), was eliminated within a few days in vaccinated fish, whereas nonprotected fish still harbored bacteria for a week after infection. Vaccinated fish reestablished normal organ structure within a few days, whereas nonprotected fish showed abnormalities up to 1 month postinfection. Protection in the early phase of infection was mainly associated with the expression of genes encoding innate factors (complement factors, lysozyme, and acute phase proteins), but in the later phase of infection, increased expression of adaptive immune genes dominated. The histological approach used has shown that the cellular changes correlated with protection of vaccinated fish. They comprised transformation of resident cells into macrophage-like cells and increased occurrence of CD8? and IgM cells, suggesting these cells as main players in protection. Future studies should investigate the causality between these factors and protection.
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Teleost skin, an ancient mucosal surface that elicits gut-like immune responses.
Proc. Natl. Acad. Sci. U.S.A.
PUBLISHED: 07-24-2013
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Skin homeostasis is critical to preserve animal integrity. Although the skin of most vertebrates is known to contain a skin-associated lymphoid tissue (SALT), very little is known about skin B-cell responses as well as their evolutionary origins. Teleost fish represent the most ancient bony vertebrates containing a SALT. Due to its lack of keratinization, teleost skin possesses living epithelial cells in direct contact with the water medium. Interestingly, teleost SALT structurally resembles that of the gut-associated lymphoid tissue, and it possesses a diverse microbiota. Thus, we hypothesized that, because teleost SALT and gut-associated lymphoid tissue have probably been subjected to similar evolutionary selective forces, their B-cell responses would be analogous. Confirming this hypothesis, we show that IgT, a teleost immunoglobulin specialized in gut immunity, plays the prevailing role in skin mucosal immunity. We found that IgT(+) B cells represent the major B-cell subset in the skin epidermis and that IgT is mainly present in polymeric form in the skin mucus. Critically, we found that the majority of the skin microbiota are coated with IgT. Moreover, IgT responses against a skin parasite were mainly limited to the skin whereas IgM responses were almost exclusively detected in the serum. Strikingly, we found that the teleost skin mucosa showed key features of mammalian mucosal surfaces exhibiting a mucosa-associated lymphoid tissue. Thus, from an evolutionary viewpoint, our findings suggest that, regardless of their phylogenetic origin and tissue localization, the chief immunoglobulins of all mucosa-associated lymphoid tissue operate under the guidance of primordially conserved principles.
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Occurrence of Diplostomum pseudospathaceum Niewiadomska, 1984 and D. mergi Dubois, 1932 (Digenea: Diplostomidae) in Danish freshwater snails: ecological and molecular data.
Folia Parasitol.
PUBLISHED: 06-04-2013
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Freshwater pulmonate snails from three locations in Lake Furesø north of Copenhagen were screened for infection with furcocercariae (by shedding in the laboratory) and recovered parasite larvae were diagnosed by molecular methods (by performing PCR of rDNA and sequencing the internal transcribed spacer [ITS] region). Overall prevalence of infection in snails was 2%. Recovered cercariae from Lymnaea stagnalis (Linnaeus) were diagnosed as Diplostomum pseudospathaceum Niewiadomska, 1984 (prevalence 4%) and cercariae from Radix balthica (Linnaeus) as D. mergi (Dubois, 1932) (prevalence 2%). Pathogen-free rainbow trout were then exposed to isolated cercariae and infection success and site location of metacercariae in these fish were determined. Infection experiments confirmed that both species could infect rainbow trout with the eye lens as infection site for the metacercarial stage although infection success differed. Combination of molecular and biological assays may contribute to improvement of our knowledge on diagnosis, distribution and biology of diplostomids in fish.
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Effects of excretory/secretory products from Anisakis simplex (Nematoda) on immune gene expression in rainbow trout (Oncorhynchus mykiss).
Fish Shellfish Immunol.
PUBLISHED: 04-09-2013
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Excretory/secretory (ES) products are molecules produced by parasitic nematodes, including larval Anisakis simplex, a parasite occurring in numerous marine fish hosts. The effects of these substances on host physiology have not been fully described. The present work elucidates the influence of ES substances on the fish immune system by measuring immune gene expression in spleen and liver of rainbow trout (Oncorhynchus mykiss) injected intraperitoneally with ES products isolated from A. simplex third stage larvae. The overall gene expression profile of exposed fish showed a generalized down-regulation of the immune genes tested, suggesting a role of ES proteins in immunomodulation. We also tested the enzymatic activity of the ES proteins and found that lipase, esterase/lipase, valine and cysteine arylamidases, naphthol-AS-BI-phosphohydrolase and ?-galactosidase activities were present in the ES solution. This type of hydrolytic enzyme activity may play a role in nematode penetration of host tissue. In addition, based on the notion that A. simplex ES products may have an immune-depressive effect (by minimizing immune gene expression) it could also be suggested that worm enzymes directly target host immune molecules which would add to a decreased host immune response and increased worm survival.
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Impact and control of protozoan parasites in maricultured fishes.
Parasitology
PUBLISHED: 03-02-2013
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SUMMARY Aquaculture, including both freshwater and marine production, has on a world scale exhibited one of the highest growth rates within animal protein production during recent decades and is expected to expand further at the same rate within the next 10 years. Control of diseases is one of the most prominent challenges if this production goal is to be reached. Apart from viral, bacterial, fungal and metazoan infections it has been documented that protozoan parasites affect health and welfare and thereby production of fish in marine aquaculture. Representatives within the main protozoan groups such as amoebae, dinoflagellates, kinetoplastid flagellates, diplomonadid flagellates, apicomplexans, microsporidians and ciliates have been shown to cause severe morbidity and mortality among farmed fish. Well studied examples are Neoparamoeba perurans, Amyloodinium ocellatum, Spironucleus salmonicida, Ichthyobodo necator, Cryptobia salmositica, Loma salmonae, Cryptocaryon irritans, Miamiensis avidus and Trichodina jadranica. The present report provides details on the parasites biology and impact on productivity and evaluates tools for diagnosis, control and management. Special emphasis is placed on antiprotozoan immune responses in fish and a strategy for development of vaccines is presented.
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Expression of immune relevant genes in rainbow trout following exposure to live Anisakis simplex larvae.
Exp. Parasitol.
PUBLISHED: 01-31-2013
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Basic immune response mechanisms in vertebrates against helminths are still poorly understood. Fish-nematode models may prove valuable for elucidation of this question. In this study we orally challenged rainbow trout (Oncorhynchus mykiss) with larvae of Anisakis simplex (Nematoda: Anisakidae) and subsequently investigated the expression of 18 immune relevant genes in spleen and liver 1, 4 and 8days post infection (d.p.i.). Gene expression data were analysed with regard to the infection status of the challenged rainbow trout at the time of necropsy; "worms rejected" (÷worms), "worms present" (+worms) and a combined group consisting of samples pooled from both previous groups (÷/+worms). No significant regulation of cytokine genes was recorded but fish which had rejected worms up-regulated the CD4 gene (6.1-fold change, 8d.p.i.) in liver. The gene encoding CD8 was significantly down-regulated 24h post challenge in livers in fish still carrying worms (2.7-fold change) but not in the worm-free group. The immunoglobulin gene IgM was significantly down-regulated (2.9-fold change, 8d.p.i.) in liver samples from the +worms group. Complement factor C3 and precerebellin genes were significantly up-regulated twofold in liver samples from infected fish 4d.p.i. Significant up-regulation of the acute-phase protein SAA was observed in all three groups and in both tissues. To our knowledge, this is the first study to describe the expression of immune genes in a fish host challenged with live nematode larvae.
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Comparative infectivity of three larval nematode species in three different salmonids.
Parasitol. Res.
PUBLISHED: 01-18-2013
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Host specificity of parasites may depend both on ecological and physiological factors. Basic descriptions of the susceptibility/resistance of fish to specific nematodes are needed in order to reveal mechanisms in the host-parasite relation. Rainbow trout (Oncorhynchus mykiss), brown trout (Salmo trutta), and Atlantic salmon (Salmo salar) were orally infected with larval stages of three different anisakid nematodes-Hysterothylacium aduncum, Contracaecum osculatum, and Anisakis simplex-and parasite survival and location was subsequently recorded for up to 14 days post infection (dpi). H. aduncum was most prevalent and numerous in brown trout 2 dpi, but a large proportion of the worms were recovered dead. No tissue penetration was observed. Rainbow trout exhibited the highest susceptibility to C. osculatum larvae at 2, 7, and 14 dpi. Mean intensities and mean abundances were lower in brown trout and salmon at all time points. The pyloric cecum was penetrated in rainbow trout on two occasions. A. simplex larvae established more successfully in salmon compared to rainbow trout; brown trout exhibited the highest natural resistance. Mean intensity and mean abundance was highest in rainbow trout at 2 and 7 dpi, but not after 14 days. A range of tissues, including muscle and liver, were found penetrated by larvae, but the pyloric ceca were the preferred microhabitat for Anisakis in both rainbow trout and salmon. It can be concluded that closely related salmonids differ in susceptibility towards different anisakid larvae and these parasites select different microhabitats in the hosts. The physiological basis for this specificity is discussed.
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Tissue specific uptake of inactivated and live Yersinia ruckeri in rainbow trout (Oncorhynchus mykiss): visualization by immunohistochemistry and in situ hybridization.
Microb. Pathog.
PUBLISHED: 01-17-2013
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Understanding of uptake and invasion routes of Yersinia ruckeri, causing Enteric Red Mouth Disease (ERM) in rainbow trout (Oncorhynchus mykiss), is essential for improved understanding of the pathogenicity and immune response mechanisms associated this disease. The present work shed light on areas of invasion in rainbow trout by the use of immunohistochemistry and in situ hybridization techniques. Fish were exposed to live or formalin inactivated bacteria and samples were subsequently taken for histology from various outer and inner surfaces. We applied a specific monoclonal antibody and specific oligonucleotide probes binding to Y. ruckeri (serotype O1, biotype 2) in tissue sections and were able to demonstrate a tissue specific uptake of this bacterium (both formalin inactivated and live form). Uptake and subsequent translocation dynamics at various surfaces demonstrated different site specific propensities between the formalin inactivated and live bacterial organisms. Lateral lines, dorsal fin, epidermis and gastro-intestinal tract mucosal tissue were the primary areas where bacterial uptake was demonstrated readily after exposure. The fate of internalized bacterial organisms within the host suggested that central immune organs are involved in the final antigen processing.
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Comparative evaluation of administration methods for a vaccine protecting rainbow trout against Yersinia ruckeri O1 biotype 2 infections.
Vet. Immunol. Immunopathol.
PUBLISHED: 01-15-2013
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Numerous outbreaks of enteric red mouth disease (ERM) caused by Yersinia ruckeri O1 biotype 2 in rainbow trout farms are currently being recorded despite established vaccination procedures against this disease. This could indicate that the currently used application of single immersion vaccination (using a commercial vaccine AquaVac(®) RELERA™) does not provide full protection. We elucidated by a controlled duplicated experiment if different vaccine administration methods can improve level and extent of protection. Rainbow trout, Oncorhynchus mykiss were vaccinated by: (1) a single immersion in bacterin diluted 1:10 for 30s (only primary vaccination); (2) two times 30s immersion (primary immersion vaccination followed by booster immersion vaccination 1 month later); (3) a single i.p. injection (only primary vaccination); (4) immersion vaccination followed by injection booster 1 month later; (5) a single 1h bath in bacterin diluted 1:2000; and (6) immersion (30s, 1:10) plus booster (1h in diluted 1:2000 vaccine) 5 months later). Injection challenge experiments were performed 3, 5 and 7 months post primary vaccination with 8.5×10(6) CFU/fish, 10.6×10(6) CFU/fish and 1×10(8) CFU/fish, respectively. In the first challenge trial, control fish exhibited a mortality of 76%, one time immersion vaccination had a mortality of 37%, two times immersion vaccinated fish had a 4% mortality, the one-time injection vaccinated group showed a mortality of 2% and the immersion plus injection boostered fish showed no mortality at all. When rainbow trout were challenged 5 months post primary vaccination, 26% mortality occurred in control fish, 21% in one time immersion group, 12% in two times immersion group, 5% in the one-time injection vaccinated group whereas immersion plus injection boostered fish again showed no mortality at all. When challenged 7 months post vaccination, one-time immersion vaccinated were not protected at all compared to the control group whereas injection vaccinated fish showed lower mortality (17%) compared to booster immersed fish (32% mortality) which was still better than un-vaccinated controls (44% mortality). It was noteworthy that a diluted bacterin (1:2000 for 1h after 5 months post primary vaccination) booster showed the same effect as a booster with 1:10 bacterin dilution for 30s applied 1 month after primary vaccination. Antibody levels showing significant elevations 28 days post challenge in vaccinated fish point to this immune parameter as a protective element. The superior and extended protection offered by booster vaccination or simply injection is noteworthy and may be applied in future vaccination strategies at farm level.
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Differential immune response of rainbow trout (Oncorhynchus mykiss) at early developmental stages (larvae and fry) against the bacterial pathogen Yersinia ruckeri.
Dev. Comp. Immunol.
PUBLISHED: 06-30-2011
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Innate immune factors play a crucial role in survival of young fish especially during early stages of life when adaptive immunity is not fully developed. In the present study, we investigated the immune response of rainbow trout (Oncorhynchus mykiss) larvae and fry at an early stage of development. We exposed 17 and 87° days post hatch larvae and fry (152 and 1118 degree days post hatch; avg. wt. 70 and 770 mg, respectively) to the bacterial pathogen, Yersinia ruckeri for 4h by bath challenge. Samples were taken at 4, 24, 72 and 96 h post exposure for qPCR and immunohistochemical analyses to elucidate the immune response mounted by these young fish. Larvae showed no mortality although infected larvae at 48 h post exposure showed hyperaemia in the mouth region and inflammation on the dorsal side of the body. Gene expression studies showed an up-regulation of iNOS and IL-22 in infected larvae 24h post exposure but most of the investigated genes did not show any difference between infected and uninfected larvae. Immunohistochemical studies demonstrated a high expression of IgT molecules in gills and CD8 positive cells in thymus of both infected and uninfected larvae. Infection of rainbow trout fry with Y. ruckeri, in contrast, induced a cumulative mortality of 74%. A high expression of cytokines (IL-1?, TNF-?, IL-22, IL-8 and IL-10), acute phase proteins (SAA, hepcidin, transferrin and precerebellin), complement factors (C3, C5 and factor B), antimicrobial peptide (cathelicidin-2) and iNOS was found in infected fry when compared to the uninfected control. IgT molecules and mannose binding lectins in gills of both infected and uninfected fry were detected by immunohistochemistry. The study indicated that early life stages (yolk-sac larvae), merely up-regulate a few genes and suggests a limited capacity of larvae to mount an immune response by gene regulation at the transcriptional level. Based on the observed clearance of bacteria and lack of mortality it could be speculated that larvae may be covered by protective shield of different immune factors providing protection against broad range of pathogens. However, the increased susceptibility of older fry suggests that Y. ruckeri may utilize some of the immune elements to enter the naive fish. The up-regulation of iNOS and IL-22 in the infected larvae implicates an important role of these molecules in immune response at early developmental stages. A dense covering of surfaces of gill filaments by IgT antibody in the young fish suggest a role of this antibody as innate immune factor at early developmental stages.
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Health of farmed fish: its relation to fish welfare and its utility as welfare indicator.
Fish Physiol. Biochem.
PUBLISHED: 05-20-2011
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This brief review focuses on health and biological function as cornerstones of fish welfare. From the function-based point of view, good welfare is reflected in the ability of the animal to cope with infectious and non-infectious stressors, thereby maintaining homeostasis and good health, whereas stressful husbandry conditions and protracted suffering will lead to the loss of the coping ability and, thus, to impaired health. In the first part of the review, the physiological processes through which stressful husbandry conditions modulate health of farmed fish are examined. If fish are subjected to unfavourable husbandry conditions, the resulting disruption of internal homeostasis necessitates energy-demanding physiological adjustments (allostasis/acclimation). The ensuing energy drain leads to trade-offs with other energy-demanding processes such as the functioning of the primary epithelial barriers (gut, skin, gills) and the immune system. Understanding of the relation between husbandry conditions, allostatic responses and fish health provides the basis for the second theme developed in this review, the potential use of biological function and health parameters as operational welfare indicators (OWIs). Advantages of function- and health-related parameters are that they are relatively straightforward to recognize and to measure and are routinely monitored in most aquaculture units, thereby providing feasible tools to assess fish welfare under practical farming conditions. As the efforts to improve fish welfare and environmental sustainability lead to increasingly diverse solutions, in particular integrated production, it is imperative that we have objective OWIs to compare with other production forms, such as high-density aquaculture. However, to receive the necessary acceptance for legislation, more robust scientific backing of the health- and function-related OWIs is urgently needed.
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Association between Yersinia ruckeri infection, cytokine expression and survival in rainbow trout (Oncorhynchus mykiss).
Fish Shellfish Immunol.
PUBLISHED: 03-15-2011
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The immune response against bacterial pathogens has been widely studied in teleosts and it is evident that survival chances differ significantly within a host population. Identification of indicators for susceptibility and responsiveness will improve our understanding of this host-pathogen interaction. The present work shows that the transcripts of cytokine genes in blood cells sampled three days post-infection was significantly higher in fish which obtained a high bacteriemia and died at later time points when compared to both non-infected control fish and infected fish that survived the infection. Rainbow trout were infected by bath challenge in a bacterial suspension (LD(60) dose, 1.8 × 10(9) CFU/ml Yersiniaruckeri for 1 h) and subsequently transferred to individual aquaria for 30 days of observation. Blood samples were analyzed for presence of Y. ruckeri both by culture and quantitative RT real-time PCR (qRT-PCR) and transcript levels of 28 genes encoding molecules which are important in the immune response. The transcript levels of a number of central cytokines, chemokines and cytokine receptors (IL-1?, IL-6, IL-8, IL-10, TNF-?, IL-receptor II) were significantly increased in infected fish that died later. In addition, a significantly higher amount of Y. ruckeri was found in the blood of the fish that died when compared to survivors. The study indicates that highly susceptible trout obtain an early heavy septicemia infection, which elicits a high up-regulation of the transcript of pro-inflammatory cytokines. Thus, less susceptible fish are protected by other factors and contract merely a weak non-lethal infection eliciting no or a weak cytokine response.
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Association between plasma antibody response and protection in rainbow trout Oncorhynchus mykiss immersion vaccinated against Yersinia ruckeri.
PLoS ONE
PUBLISHED: 03-04-2011
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A key hallmark of the vertebrate adaptive immune system is the generation of antigen-specific antibodies from B cells. Fish are the most primitive gnathostomes (jawed vertebrates) possessing an adaptive immune system. Vaccination of rainbow trout against enteric redmouth disease (ERM) by immersion in Yersinia ruckeri bacterin confers a high degree of protection to the fish. The immune mechanisms responsible for protection may comprise both cellular and humoral elements but the role of specific immunoglobulins in this system has been questioned and not previously described. The present study demonstrates significant increase in plasma antibody titers following immersion vaccination and significantly reduced mortality during Y. ruckeri challenge.Rainbow trout were immersion-vaccinated, using either a commercial ERM vaccine (AquaVac™ ERM vet) or an experimental Y. ruckeri bacterin. Half of the trout vaccinated with AquaVac™ ERM vet received an oral booster (AquaVac™ ERM Oral vet). Sub-groups of the fish from each group were subsequently exposed to 1 x 10? CFU Y. ruckeri/ml either eight or twenty-six weeks post vaccination (wpv). All vaccinated groups showed 0% mortality when challenged, which was highly significant compared to the non-vaccinated controls (40 and 28% mortality eight and twenty-six weeks post vaccination (wpv), respectively) (P<0.0001). Plasma samples from all groups of vaccinated fish were taken 0, 4, 8, 12, 16 and 26 wpv. and Y. ruckeri specific IgM antibody levels were measured with ELISA. A significant increase in titers was recorded in vaccinated fish, which also showed a reduced bacteremia during challenge. In vitro plasma studies showed a significantly increased bactericidal effect of fresh plasma from vaccinated fish indicating that plasma proteins may play a role in protection of vaccinated rainbow trout.
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Cysteine proteases as potential antigens in antiparasitic DNA vaccines.
Vaccine
PUBLISHED: 02-17-2011
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Cysteine proteases in parasites are potent inducers of vertebrate host immune responses and may under certain circumstances take part in the pathogens immune evasion strategies. These capacities place these parasite molecules as interesting candidate antigens in antiparasitic vaccines for use in vertebrates. Parasite cysteine proteases are able to skew the Th1/Th2 profile in mammals towards a response which allows sustainable parasite burdens in the host. DNA vaccines are also able to skew the Th1/Th2 profile by different administration techniques and the use of cysteine proteases in these genetic immunizations open perspectives for manipulation of the host immune response towards higher protection.
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Cellular and humoral factors involved in the response of rainbow trout gills to Ichthyophthirius multifiliis infections: molecular and immunohistochemical studies.
Fish Shellfish Immunol.
PUBLISHED: 01-11-2011
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The parasitic ciliate Ichthyophthirius multifiliis infecting skin, fins and gills of fish induces a protective immune response in rainbow trout (Oncorhynchus mykiss) surviving the infection and a similar protection can be conferred by i.p. injection of live theronts. A combined molecular and immunohistochemical approach has been used in this work for pinpointing cellular and humoral immune factors in gill tissue involved in the response and indicating interactions between the systemic and local responses. Fish were immunized by intra-peritoneal injection of live I. multifiliis theronts, control fish were injected with PBS and subgroups were treated with the immuno-suppressant hydrocortisone before fish were challenged with live theronts. Significant up-regulations of genes encoding IgM, IgT, C3, SAA, IL-8, IL-22 and IFN-? were induced by immunization and challenge. Hydrocortisone treatment had a significant down-regulating effect on genes incoding IgT, IgM, CD4, CD8, IFN-?, IL-8 and IL-22 in all groups. Immunohistochemistry, using monoclonal antibodies to detect cellular markers, demonstrated active involvement of CD8, MHC II, IgT and IgM positive cells in gill tissue. Putative T-cells (CD8 positive cells) were detected in the intraepithelial lymphoid tissue located at the base of gill filaments and in hyperplastic gill tissue but following infection a clear efflux of these cells was detected. MHC II positive cells were distributed across the gill filaments and accumulated in hyperplastic tissue but hydrocortisone treatment affected their density negatively in both immunized and non-immunized fish. IgT positive cells were present in the epithelial lining of the gill lamellae (suggesting a primary role of this protein in the mucosal defence against the ciliate) whereas IgM positive cells were found only in gill arterioles and the lamellar capillaries. The present work indicates an intensive activity and specialized function of immune cells (B-cells, T-cells and macrophages) and humoral elements such as immunoglobulins IgT and IgM which are orchestrated by cytokines in gill tissue reacting against I. multifiliis.
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PAMP induced expression of immune relevant genes in head kidney leukocytes of rainbow trout (Oncorhynchus mykiss).
Dev. Comp. Immunol.
PUBLISHED: 10-12-2010
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Host immune responses elicited by invading pathogens depend on recognition of the pathogen by specific receptors present on phagocytic cells. However, the reactions to viral, bacterial, parasitic and fungal pathogens vary according to the pathogen-associated molecular patterns (PAMPs) on the surface of the invader. Phagocytic cells are known to initiate a respiratory burst following an exposure to the pathogen, but the underlying and associated specific elements are poorly elucidated in fish. The present study describes the differential response of head kidney leukocytes from rainbow trout (Oncorhynchus mykiss) to different PAMPs mimicking viral (poly I:C), bacterial (flagellin and LPS) and fungal infections (zymosan and ?-glucan). Transcript of cytokines related to inflammation (IL-1?, IL-6, IL-10 and TNF-?) was highly up-regulated following LPS exposure whereas flagellin or poly I:C induced merely moderate reactions. In contrast, IFN-? expression was significantly higher in the poly I:C stimulated group compared to the LPS group. When head kidney cells were exposed to zymosan or ?-glucan, genes encoding IL-1?, TNF-?, IL-6 and IL-10 became up-regulated. Their level of up-regulation was comparable to LPS but the kinetics differed. In particular, TNF-? induction was considerably slower when stimulated with zymosan or ?-glucan. The gene encoding the COX-2 enzyme, a central element during initiation of inflammatory reactions, was significantly higher in stimulated cells although a depressing effect of high concentrations of LPS and zymosan became evident after 4h exposure. This study suggests that rainbow trout leukocytes respond differently to viral, bacterial and fungal PAMPs, which may reflect activation of specific signaling cascades eventually leading to activation of different immune effector molecules.
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Ribosomal RNA gene sequences confirm that protistan endoparasite of larval cod Gadus morhua is Ichthyodinium sp.
Dis. Aquat. Org.
PUBLISHED: 03-16-2010
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An enigmatic protistan endoparasite found in eggs and larvae of cod Gadus morhua and turbot Psetta maxima was isolated from Baltic cod larvae, and DNA was extracted for sequencing of the parasites small subunit ribosomal RNA (SSU rRNA) gene. The endoparasite has previously been suggested to be related to Ichthyodinium chabelardi, a dinoflagellate-like protist that parasitizes yolk sacs of embryos and larvae of a variety of fish species. Comparison of a 1535 bp long fragment of the SSU rRNA gene of the cod endoparasite showed absolute identity with I. chabelardi, demonstrating that the 2 parasites are very closely related, if not identical. This finding is discussed in relation to some morphological differences that appear to exist between I. chabelardi and the cod endoparasite.
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Innate immune response in rainbow trout (Oncorhynchus mykiss) against primary and secondary infections with Yersinia ruckeri O1.
Dev. Comp. Immunol.
PUBLISHED: 05-27-2009
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Response mechanisms in teleosts against bacterial pathogens have been widely studied following injection procedures applying preparations of killed bacteria. In contrast, investigations on immune reactions in fish which have survived a primary infection and subsequently have been challenged are few or lacking. However, knowledge on these factors during infection and re-infection could provide the basis for development of improved vaccines. The innate immune response in rainbow trout (Oncorhynchus mykiss) against Yersinia ruckeri O1 has been studied following a primary intra-peritoneal injection with 5 x 10(5) CFU Y. ruckeri, and after bacterial clearance a secondary infection 35 days later. The number of pathogens in the liver was measured with a Y. ruckeri specific 16S ribosomal RNA quantitative real-time RT-PCR (q-PCR) during the course of infection. The bacterial counts peaked on day 3 during the primary infection and were significantly lower during the re-infection. Re-challenged fish showed a highly increased survival when compared to the naïve fish receiving a primary infection indicating development of adaptive immunity in the fish against this bacterial pathogen. We investigated the gene expression of innate immune factors in the liver during infections in order to elucidate molecules involved in survival of hosts before adaptive immunity was mounted. Transcription of mRNA was measured in liver samples taken 8 h, 1, 3, 7, 14 and 28 d post-infection using q-PCR. The investigation focused on genes encoding toll-like receptor 5 (TLR5), the pro-inflammatory cytokines IL-1beta, IL-6 and TNF-alpha, the acute phase proteins (APPs) serum amyloid protein a (SAA), trout C polysaccharide binding protein, a CRP/SAP like pentraxin, precerebellin, transferrin, hepcidin and finally the complement factors C3, C5 and factor B. Infection elicited significantly increased gene expression of all the cytokines (IL-6 > 1000-fold), some acute phase proteins (SAA > 3000-fold) and down-regulation of complement factors (C3, C5 and factor B). SAA expression was significantly earlier activated during the re-infection when compared to the primary infection. The pattern of gene activation suggested that the innate response was based on pathogen binding to toll-like receptors, production of cytokines and subsequent release of APPs. In general, both the innate immune response and the amount of Y. ruckeri measured in the liver during the re-infection was much lower compared to the first infection, probably reflecting development of adaptive immunity.
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Life cycle stages of heterophyid trematodes in Vietnamese freshwater fishes traced by molecular and morphometric methods.
Vet. Parasitol.
PUBLISHED: 04-15-2009
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A survey of digenean zoonotic trematodes infecting snails and fishes in a North Vietnamese freshwater fish culture system revealed shedding of three types of parapleurolophocercous cercariae from the snail host Melanoides tuberculata and the presence of metacercariae within the genus Haplorchis (H. pumilio and H. taichui) and Procerovum sp. in tissues of cultured fishes (silver carp, Indian carp and climbing perch). No morphological characters were able to link the different cercariae specifically to any of the metacercariae. Subsequent molecular work including PCR and sequencing of ribosomal DNA (the ITS2 region) in cercariae and metacercariae associated only one type of the cercariae to the recovered H. pumilio metacercariae. Further, full identity (100%) was found with regard to the ITS sequence of adult H. pumilio obtained from the same North Vietnamese region. None of the cercariae showed sequence identities with H. taichui but more than 99% identity was found between one cercaria type and the Procerovum sp. metacercaria. It was indicated that trematode parasites of farmed fishes may originate from sources outside the fish ponds and may be introduced as free-swimming cercariae when pond water is being replenished by river water. Likewise, cercariae from the ponds may not always result in metacercarial infections of the farmed fishes. The present study frames the needs for including molecular techniques as auxiliary tools when conducting ecological studies of cercariae in complex ecosystems. The parasites recorded in the fish ponds are not only known to affect the health of aquacultured fishes but also the documented zoonotic potential of the diagnosed metacercaria calls for alerts regarding human consumption of raw or inadequately processed fish dishes.
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Response of rainbow trout (Oncorhynchus mykiss) in skin and fin tissue during infection with a variant of Gyrodactylus salaris (Monogenea: Gyrodactylidae).
Folia Parasitol.
PUBLISHED: 02-25-2009
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Response mechanisms of rainbow trout Oncorhynchus mykiss (Walbaum), experimentally infected with a Danish strain of Gyrodactylus salaris Malmberg, 1957 were investigated using molecular tools (qPCR) and immunohistochemistry. Expression of ten immune-relevant genes and reactivity with five different antibodies in the epidermis of skin and fin tissue were analysed in susceptible but responding rainbow trout. Rainbow trout were susceptible with regard to the parasite strain which initially colonised fins but relocated to the body region as infection progressed. The ten investigated genes encoding the cytokines IL-1beta, TNF-alpha, IFN-gamma, IL-10 and markers for adaptive immune activity, such as CD-4, CD-8, TCR-alpha, IgM, IgT and MHC II, were not found significantly regulated during the course of infection although IFN-gamma showed a slight up-regulation. Immunohistochemical analyses showed positive reactivity with antibodies against CD3, B-lymphocytes, neutrophilic granulocytes and collectin but not with mAb against IgM. No staining differences between infected and non-infected skin and fin tissue were detected.
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Inflammatory response of rainbow trout Oncorhynchus mykiss (Walbaum, 1792) larvae against Ichthyophthirius multifiliis.
Fish Shellfish Immunol.
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At hatching, the immune system of the rainbow trout larva is not fully developed. The larva emerges from the egg and is exposed to the aquatic freshwater environment containing pathogenic organisms. At this early stage, protection from disease causing organisms is thought to depend on innate immune mechanisms. Here, we studied the ability of young post-hatch rainbow trout larvae to respond immunologically to an infection with Ichthyophthirius multifiliis and also report on the localization of 5 different immune relevant molecules in the tissue of infected and uninfected larvae. Quantitative RT-PCR (qPCR) was used to analyze the genetic regulation of IL-1?, IL-8, IL-6, TNF-?, iNOS, SAA, cathelicidin-2, hepcidin, IL-10, IL-22, IgM and IgT. Also, a panel of 5 monoclonal antibodies was used to investigate the presence and localization of the proteins CD8, SAA, MHCII, IgM and IgT. At 10 days (84 degree days) post-hatching, larvae were infected with I. multifiliis and sampled for qPCR at 3, 6, 12, 24, 48 and 72 h post-infection (p.i.). At 72 h p.i. samples were taken for antibody staining. The first of the examined genes to be up-regulated was IL-1?. Subsequently, IL-8 and cathelicidin-2 were up-regulated and later TNF-?, hepcidin, IL-6, iNOS and SAA. Immunohistochemical staining showed presence of CD8 and MHCII in the thymus of both infected and non-infected larvae. Staining of MHCII and SAA was seen at sites of parasite localization and weak staining of SAA was seen in the liver of infected larvae. Staining of IgT was seen at site of infection in the gills which may be one of the earliest adaptive factors seen. No positive staining was seen for IgM. The study illustrates that rainbow trout larvae as young as 10 days (84 degree days) post-hatch are able to regulate important immune relevant cytokines, chemokines and acute phase proteins in response to infection with a skin parasitizing protozoan parasite.
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Determining vaccination frequency in farmed rainbow trout using Vibrio anguillarum O1 specific serum antibody measurements.
PLoS ONE
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Despite vaccination with a commercial vaccine with a documented protective effect against Vibrio anguillarum O1 disease outbreaks caused by this bacterium have been registered among rainbow trout at Danish fish farms. The present study examined specific serum antibody levels as a valid marker for assessing vaccination status in a fish population. For this purpose a highly sensitive enzyme-linked immunosorbent assay (ELISA) was developed and used to evaluate sera from farmed rainbow trout vaccinated against V. anguillarum O1.
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Approaches towards DNA vaccination against a skin ciliate parasite in fish.
PLoS ONE
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Rainbow trout (Oncorhynchus mykiss) were immunized with plasmid DNA vaccine constructs encoding selected antigens from the parasite Ichthyophthirius multifiliis. Two immobilization antigens (I-ags) and one cysteine protease were tested as genetic vaccine antigen candidates. Antigenicity was evaluated by immunostaining of transfected fish cells using I-ag specific mono- and polyclonal antibodies. I. multifiliis specific antibody production, regulation of immune-relevant genes and/or protection in terms of parasite burden or mortality was measured to evaluate the induced immune response in vaccinated fish. Apart from intramuscular injection, needle free injection and gene gun delivery were tested as alternative administration techniques. For the I-ags the complement protein fragment C3d and the termini of the viral haemorrhagic septicaemia virus glyco(G)protein (VHSV G) were tested as opsonisation and cellular localisation mediators, respectively, while the full length viral G protein was tested as molecular adjuvant. Expression of I-ags in transfected fish cells was demonstrated for several constructs and by immunohistochemistry it was possible to detect expression of a secreted form of the Iag52B in the muscle cells of injected fish. Up-regulations of mRNA coding for IgM, MHC I, MHC II and TCR ?, respectively, were observed in muscle tissue at the injection site in selected trials. In the spleen up-regulations were found for IFN-? and IL-10. The highest up-regulations were seen following co-administration of I-ag and cysteine protease plasmid constructs. This correlated with a slight elevation of an I. multifiliis specific antibody response. However, in spite of detectable antigen expression and immune reactions, none of the tested vaccination strategies provided significant protection. This might suggest an insufficiency of DNA vaccination alone to trigger protective mechanisms against I. multifiliis or that other or additional parasite antigens are required for such a vaccine to be successful.
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Tetracapsuloides bryosalmonae and PKD in juvenile wild salmonids in Denmark.
Dis. Aquat. Org.
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The myxozoan Tetracapsuloides bryosalmonae is the causative agent of proliferative kidney disease (PKD), a widespread and serious condition in salmonid fishes in Europe and North America. In Europe, PKD is primarily reported affecting farmed rainbow trout Oncorhynchus mykiss, but limited information exists on the occurrence and effects of T. bryosalmonae in wild salmonids. We investigated the presence of T. bryosalmonae in salmonids in Denmark and found that the parasite is common in the dominant wild Danish salmonid, brown trout Salmo trutta, and that it also appears in wild Atlantic salmon S. salar. Clinical signs of PKD were present in some brown trout, but in most cases the parasite was found through histology and/or PCR investigations of kidney tissue in fish that showed no signs of infection. Even though there was high similarity between internal transcribed spacer 1 (ITS1) sequences of T. bryosalmonae from wild brown trout, Atlantic salmon and farmed rainbow trout, a geographic pattern was indicated among T. bryosalmonae ITS1 phylotypes. None of the investigated streams were found free of T. bryosalmonae, but prevalence of the parasite was highly variable.
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Microhabitat preference of Anisakis simplex in three salmonid species: immunological implications.
Vet. Parasitol.
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Three salmonid fish species, Oncorhynchus mykiss, Salmo salar and Salmo trutta, were infected experimentally with the parasitic nematode Anisakis simplex (A. simplex) and the difference between in vivo behaviour of the nematode in the three fish species was investigated. Infection success rate differed between species. S. salar (Baltic salmon) showed the highest number of successfully established nematodes, whereas S. trutta (brown trout) and O. mykiss (rainbow trout) had a higher natural resistance. Microhabitat selection of nematodes differed according to fish species. In brown trout, A. simplex larvae were attached to the digestive tract (stomach, pyloric caeca, intestine), while the majority of larvae found in rainbow trout were located between the pyloric caeca. In Baltic salmon, nematodes were dispersed in and on spleen, head kidney, liver, swim bladder and musculature. Encapsulation and inflammatory cellular reactions differed accordingly. Histopathological and immunohistochemical studies using monoclonal antibodies raised against salmonid IgM, CD8 and MHCII were performed to detect the presence of immune cells around the infecting nematodes. None of the three fish species showed positive reactions for IgM-bearing cells in the inflammatory tissue connected with nematodes. CD8+ cells were detected in all three species and MHCII-bearing cells were found associated with encapsulated A. simplex in rainbow trout and brown trout, but not in Baltic salmon. Physiological, immunological and pathological implications of microhabitat differences are discussed.
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Immunomodulatory effects of dietary ?-1,3-glucan from Euglena gracilis in rainbow trout (Oncorhynchus mykiss) immersion vaccinated against Yersinia ruckeri.
Fish Shellfish Immunol.
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Potential immunostimulatory effects of orally administered ?-glucan were investigated in combination with immersion vaccination against enteric redmouth disease caused by Yersinia ruckeri in rainbow trout (Oncorhynchus mykiss). A linear, unbranched and pure (purity ?98%) ?-1,3-glucan (syn. paramylon) from the alga Euglena gracilis was applied at an inclusion level of 1% ?-glucan in feed administered at a rate of 1% biomass day(-1) for 84 consecutive days. Fish were vaccinated after two weeks of experimental feeding and bath challenged with live Y. ruckeri six weeks post-vaccination. Blood and head kidney were sampled at day 0, 13 (1 day pre-vaccination), 15, 55, 59 (day 3 post-challenge (p.c.)), 70 and 84. Vaccination induced significantly increased survival p.c., whereas the ?-glucan had no effect on survival in either unvaccinated or vaccinated fish. Expression in head kidney of genes related to the acute phase response, i.e. interleukin-1? (IL-1?), serum amyloid A (SAA), precerebellin, and hepcidin, was significantly different in vaccinated fish receiving ?-glucan compared to vaccinated controls at day 3 p.c., while no effect of ?-glucan was observed among unvaccinated fish. Significant interaction between ?-glucan and vaccination was found for the regulation of IL-1?, tumour necrosis factor-?, interferon-?, SAA, precerebellin and hepcidin p.c. For SAA, the significant effect of ?-glucan in vaccinated fish persisted at day 14 p.c. and 28 p.c. The difference in gene expression among vaccinated fish was mainly observed as down-regulations in vaccinated, ?-glucan fed fish compared to up-regulations or no regulation in vaccinated controls. Slightly increased levels of plasma lysozyme activity were found in fish (both unvaccinated and vaccinated) receiving ?-glucan at day 3 p.c. compared to control fed groups. This was associated with a faster clearance of Y. ruckeri in unvaccinated fish receiving ?-glucan. In contrast to the trend towards a beneficial effect of ?-glucan on plasma lysozyme activity, a trend towards suppression of plasma antibodies was seen in both unvaccinated and vaccinated fish receiving ?-glucan. However, the effects of ?-glucan were not reflected in the survival curves, and the differences seen in plasma lysozyme activity and antibody levels may have counteracted and set off each other as well as counteracted any potential effect represented by the differences in gene expression found.
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Myxobolus groenlandicus n. sp. (Myxozoa) distorting skeletal structures and musculature of Greenland halibut Reinhardtius hippoglossoides (Teleostei: Pleuronectidae).
Dis. Aquat. Org.
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A specimen of Greenland halibut Reinhardtius hippoglossoides (Walbaum, 1792) caught on the west coast of Greenland (Qasigiannguit) was found to possess serious pathological changes in the body musculature. A series of cartilaginous cylindrical structures organized symmetrically at the position of the proximal pterygiophores had changed the musculature and produced irreversible distortions (cavities and holes) in the fillet of the processed fish, leaving it with no value for the industry. Histopathological investigation showed that these structures consisted of hypertrophic cartilage containing numerous myxospore-producing plasmodia. Morphometric and molecular analyses of the parasites showed that both spore morphology and rDNA sequences complied with characteristics of the genus Myxobolus, but no full affiliation with a known species could be found. The parasite is a previously undescribed species, and the name Myxobolus groenlandicus n. sp. is assigned to this new myxobolid.
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Baltic salmon, Salmo salar, from Swedish river Lule älv is more resistant to furunculosis compared to rainbow trout.
PLoS ONE
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Furunculosis, caused by Aeromonas salmonicida, continues to be a major health problem for the growing salmonid aquaculture. Despite effective vaccination programs regular outbreaks occur at the fish farms calling for repeated antibiotic treatment. We hypothesized that a difference in natural susceptibility to this disease might exist between Baltic salmon and the widely used rainbow trout.
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