RÉSUMÉ
Introduction: Little is known about the proteomic changes at the portals of entry in rainbow trout after infection with the myxozoan parasites, Myxobolus cerebralis, and Tetracapsuloides bryosalmonae. Whirling disease (WD) is a severe disease of salmonids, caused by the myxosporean M. cerebralis, while, proliferative kidney disease (PKD) is caused by T. bryosalmonae, which instead belongs to the class Malacosporea. Climate change is providing more suitable conditions for myxozoan parasites lifecycle, posing a high risk to salmonid aquaculture and contributing to the decline of wild trout populations in North America and Europe. Therefore, the aim of this study was to provide the first proteomic profiles of the host in the search for evasion strategies during single and coinfection with M. cerebralis and T. bryosalmonae. Methods: One group of fish was initially infected with M. cerebralis and another group with T. bryosalmonae. After 30 days, half of the fish in each group were co-infected with the other parasite. Using a quantitative proteomic approach, we investigated proteomic changes in the caudal fins and gills of rainbow trout before and after co-infection. Results: In the caudal fins, 16 proteins were differentially regulated post exposure to M. cerebralis, whereas 27 proteins were differentially modulated in the gills of the infected rainbow trout post exposure to T. bryosalmonae. After co-infection, 4 proteins involved in parasite recognition and the regulation of host immune responses were differentially modulated between the groups in the caudal fin. In the gills, 11 proteins involved in parasite recognition and host immunity, including 4 myxozoan proteins predicted to be virulence factors, were differentially modulated. Discussion: The results of this study increase our knowledge on rainbow trout co-infections by myxozoan parasites and rainbow trout immune responses against myxozoans at the portals of entry, supporting a better understanding of these host-parasite interactions.
Sujet(s)
Co-infection , Maladies des poissons , Myxobolus , Myxozoa , Oncorhynchus mykiss , Parasitoses animales , Protéomique , Animaux , Oncorhynchus mykiss/parasitologie , Oncorhynchus mykiss/immunologie , Maladies des poissons/parasitologie , Maladies des poissons/immunologie , Parasitoses animales/immunologie , Parasitoses animales/parasitologie , Co-infection/parasitologie , Co-infection/médecine vétérinaire , Co-infection/immunologie , Interactions hôte-parasite/immunologie , Protéome , Branchies/parasitologie , Branchies/immunologie , Branchies/métabolismeRÉSUMÉ
Nodular gill disease (NGD) is an emerging condition associated with amoeba trophozoites in freshwater salmonid farms. However, unambiguous identification of the pathogens still must be achieved. This study aimed to identify the amoeba species involved in periodic NGD outbreaks in two rainbow trout (Oncorhynchus mykiss) farms in Northeastern Italy. During four episodes (February-April 2023), 88 fish were euthanized, and their gills were evaluated by macroscopic, microscopic and histopathological examination. The macroscopic and microscopic severity of the lesions and the degree of amoebae infestation were scored and statistically evaluated. One gill arch from each animal was put on non-nutrient agar (NNA) Petri dishes for amoeba isolation, cultivation and subsequent identification with SSU rDNA sequencing. Histopathology confirmed moderate to severe lesions consistent with NGD and mild to moderate amoeba infestation. The presence of amoebae was significantly correlated with lesion severity. Light microscopy of cultured amoebae strains and SSU rDNA analysis revealed the presence of a previously characterized amoeba Naegleria sp. strain GERK and several new strains: two strains from Hartmannelidae, three vannelid amoebae from the genus Ripella and cercozoan amoeba Rosculus. Despite the uncertainty in NGD etiopathogenesis and amoebae pathogenic role, identifying known and new amoebae leans towards a possible multi-aetiological origin.
Sujet(s)
Amibiase , Maladies des poissons , Branchies , Oncorhynchus mykiss , Animaux , Oncorhynchus mykiss/parasitologie , Maladies des poissons/parasitologie , Maladies des poissons/épidémiologie , Italie , Amibiase/médecine vétérinaire , Amibiase/parasitologie , Branchies/parasitologie , Branchies/anatomopathologie , Amoeba/génétique , Amoeba/isolement et purification , Amoeba/classification , Aquaculture , Amoebozoa/génétique , Amoebozoa/isolement et purification , Amoebozoa/classification , Amoebozoa/physiologie , PhylogenèseRÉSUMÉ
Salmincola californiensis is a parasitic copepod of freshwater salmonids in the North Pacific rim countries. Sixteen adult females of the species were found alive on the gills of an ocean-age 4, maturing steelhead trout, Oncorhynchus mykiss, caught in offshore waters (50°30'N, 179°30'W) of the North Pacific Ocean in July 1997. This is the first evidence of live individuals of S. californiensis from ocean-migrating salmonids. When found, copepods were attached to the distal ends of gill filaments, and their bodies were observed to be slowly moving in Petri dishes with seawater. Ocean-migrating steelhead trout comprise individuals originating from western Kamchatka (Russia) and western North America. Based on the date and catch location of the infected fish, it is inferred that it originated from western North America, where it acquired S. californiensis infection in fresh water. As this fish spent about 4 years in the ocean, the copepods likely survived the same period at sea. However, if the fish was a kelt, the survival period of the copepods in the ocean may be shorter than four years. To confirm identification of the copepods, adult females of S. californiensis are briefly described using the specimens collected from the fish.
Sujet(s)
Copepoda , Maladies des poissons , Oncorhynchus mykiss , Parasites , Femelle , Animaux , Oncorhynchus mykiss/parasitologie , Branchies/parasitologie , Eau douce , Océans et mers , Maladies des poissons/parasitologieRÉSUMÉ
The myxozoan Ceratonova shasta was described from hatchery rainbow trout over 70 years ago. The parasite continues to cause severe disease in salmon and trout, and is recognized as a barrier to salmon recovery in some rivers. This review incorporates changes in our knowledge of the parasite's life cycle, taxonomy and biology and examines how this information has expanded our understanding of the interactions between C. shasta and its salmonid and annelid hosts, and how overarching environmental factors affect this hostparasite system. Development of molecular diagnostic techniques has allowed discrimination of differences in parasite genotypes, which have differing host affinities, and enabled the measurement of the spatio-temporal abundance of these different genotypes. Establishment of the C. shasta life cycle in the laboratory has enabled studies on hostparasite interactions and the availability of transcriptomic data has informed our understanding of parasite virulence factors and host defences. Together, these advances have informed the development of models and management actions to mitigate disease.
Sujet(s)
Cnidaria , Maladies des poissons , Myxozoa , Oncorhynchus mykiss , Parasites , Parasitoses animales , Animaux , Parasitoses animales/parasitologie , Maladies des poissons/parasitologie , Oncorhynchus mykiss/parasitologieRÉSUMÉ
Temperature and intraspecific competition are important factors influencing the growth of all organisms, including parasites. The temperature increase is suggested to stimulate the development of parasites within poikilothermic hosts. However, at high parasite densities, this effect could be diminished, due to stronger intraspecific competition. Our study, for the first time, addressed the joint effects of warming and parasite abundances on parasite growth in poikilothermic hosts. The growth of the common fish parasite larvae (trematode Diplostomum pseudospathaceum) within the rainbow trout at different infection intensities and temperatures (15°C and 18°C) was experimentally investigated. The results showed that temperature was positively correlated with both parasite infection success and growth rates. The growth rates increased much more compared to those in many free-living poikilothermic animals. Atypically for a majority of parasites, D. pseudospathaceum larvae grow faster when abundant (Allee effect). The possible causes for this phenomenon (manipulation cost sharing, etc.) are discussed in this study. Importantly, limited evidence of the interaction between temperature and population density was found. It is likely that temperature did not change the magnitude of the Allee effect but affected its timing. The impact of these effects is supposed to become more pronounced in freshwater ecosystems under current climate changes.
Sujet(s)
Maladies des poissons , Oncorhynchus mykiss , Parasites , Trematoda , Infections à trématodes , Animaux , Écosystème , Maladies des poissons/parasitologie , Interactions hôte-parasite , Oncorhynchus mykiss/parasitologie , Température , Infections à trématodes/parasitologie , Infections à trématodes/médecine vétérinaireRÉSUMÉ
The intercellular adhesion molecule-1 (ICAM-1), known as CD54, is a transmembrane cell surface glycoprotein that interacts with two integrins (i.e., LFA-1 and Mac-l) important for trans-endothelial migration of leukocytes. The level of ICAM-1 expression is upregulated in response to some inflammatory stimulations, including pathogen infection and proinflammatory cytokines. Yet, to date, our knowledge regarding the functional role of ICAM-1 in teleost fish remains largely unknown. In this study, we cloned and characterized the sequence of ICAM-1 in rainbow trout (Oncorhynchus mykiss) for the first time, which exhibited that the molecular features of ICAM-1 in fishes were relatively conserved compared with human ICAM-1. The transcriptional level of ICAM-1 was detected in 12 different tissues, and we found high expression of this gene in the head kidney, spleen, gills, skin, nose, and pharynx. Moreover, upon stimulation with infectious hematopoietic necrosis virus (IHNV), Flavobacterium columnare G4 (F. columnare), and Ichthyophthirius multifiliis (Ich) in rainbow trout, the morphological changes were observed in the skin and gills, and enhanced expression of ICAM-1 mRNA was detected both in the systemic and mucosal tissues. These results indicate that ICAM-1 may be implicated in the mucosal immune responses to viral, bacterial, and parasitic infections in teleost fish, meaning that ICAM-1 emerges as a master regulator of mucosal immune responses against pathogen infections in teleost fish.
Sujet(s)
Infections à ciliophores , Maladies des poissons/immunologie , Protéines de poisson/immunologie , Infections à Flavobacteriaceae , Régulation de l'expression des gènes/immunologie , Molécule-1 d'adhérence intercellulaire/immunologie , Oncorhynchus mykiss , Infections à Rhabdoviridae , Animaux , Infections à ciliophores/immunologie , Infections à ciliophores/médecine vétérinaire , Infections à Flavobacteriaceae/immunologie , Infections à Flavobacteriaceae/médecine vétérinaire , Flavobacterium/immunologie , Hymenostomatida/immunologie , Virus de la nécrose hématopoïétique infectieuse/immunologie , Oncorhynchus mykiss/immunologie , Oncorhynchus mykiss/microbiologie , Oncorhynchus mykiss/parasitologie , Oncorhynchus mykiss/virologie , Infections à Rhabdoviridae/immunologie , Infections à Rhabdoviridae/médecine vétérinaireRÉSUMÉ
BACKGROUND: In Norway, x-cell parasites associated with disease in farmed salmonids have been known as a rare phenomenon for two decades. These parasites cause systemic infections in farmed rainbow trout (Oncorhynchus mykiss) and Atlantic salmon (Salmo salar), but have so far not been characterized and described. METHODS: The x-cells from several cases of diseased fish were studied using light and electron microscopy, and by phylogenetic analysis based on small subunit ribosomal RNA (SSU rRNA) gene sequences. RESULTS: We describe here the x-cell parasite as a new species in a new genus, Salmoxcellia vastator n. gen., n. sp. Phylogenetic analyses placed Salmoxcellia n. gen. together with Gadixcellia among the xcelliids, a group of perkinsozoan alveolates. The new genus and species were found to have vacuolate plasmodial x-cells filled with lipid droplets, and an electron-dense alveolar pellicle. Electron-dense cytoplasmic inclusions, which are characteristic of the other xcelliid genera Xcellia and Gadixcellia, are lacking in Salmoxcellia n. gen. These x-cell plasmodia divide by plasmotomy and occur as aggregates in the host tissues, particularly in blood-rich tissues such as those of the kidney, red musculature, heart and liver. Host reaction and the refractive lipid droplets in the x-cells result in S. vastator n. gen., n. sp. aggregates appearing as white patches in the tissues. CONCLUSIONS: We describe a new genus and species of xcelliid protist parasites from two very important farmed fish species and provide molecular methods for detection. The new parasite is associated with disease, but more importantly it has a spoiling effect on farmed salmonid fillets, rendering them unsuitable for sale. Consequently, this parasite represents a threat to the aquaculture industry.
Sujet(s)
Maladies des poissons/parasitologie , Pêcheries/statistiques et données numériques , Oncorhynchus mykiss/parasitologie , Parasites/classification , Parasites/génétique , Phylogenèse , Salmo salar/parasitologie , Animaux , Aquaculture , Séquence nucléotidique/génétique , Norvège , Parasites/isolement et purificationRÉSUMÉ
The polyopisthocotylean Discocotyle sagittata is a blood-feeding monogenean that infects the gill lamellae of rainbow trout, Oncorhynchus mykiss, and brown trout, Salmo trutta. The ultrastructure of their alimentary tract, at different stages of the life cycle, was previously unknown. Here, we show that the gastrodermis of the oncomiracidium, subadult, and adult D. sagittata follows the same structural organization as that of other blood-feeding polyopisthocotyleans, being composed of digestive cells alternating with a connecting syncytium. Digestive cells of the oncomiracidium are found in three developmental forms: undifferentiated, developing differentiated, and differentiated (presumably functioning) cells whereas those of adult and subadult are present in a single functioning state with variable size and content. The apical cytoplasm of adult digestive cells forms conical outgrowths, a feature which is absent in the oncomiracidium. The connecting syncytium of the oncomiracidium has no evidence of metabolic activity, while that of adult and subadult is metabolically active. The lamellae of the connecting syncytium of adults and subadults are more numerous and larger, and their terminal portions are expanded, compared with those of the oncomiracidium. Parallel, tubular, membranous structures are characteristic of the apical cytoplasm of the connecting syncytium of the oncomiracidium. Luminal lamella in the oncomiracidium, subadult, and adult form balloon-like structures enclosing some luminal contents, but those of the oncomiracidium are larger, bounded by nucleated cytoplasmic layer, and enclose more luminal contents. The possible functions of these structures and mechanism of digestion in both oncomiracidium and adult are discussed.
Sujet(s)
Oncorhynchus mykiss , Trematoda , Animaux , Cytoplasme , Branchies/parasitologie , Oncorhynchus mykiss/parasitologie , Trematoda/ultrastructureRÉSUMÉ
Ichthyophthirius multifiliis is a major pathogen that causes a high mortality rate in trout farms. However, systemic responses to the pathogen and its interactions with multiple organs during the course of infection have not been well described. In this study, dual-organ transcriptomic responses in the liver and head kidney and hemato-serological indexes were profiled under I. multifiliis infection and recovery to investigate systemic immuno-physiological characteristics. Several strategies for massive transcriptomic interpretation, such as differentially expressed genes (DEGs), Poisson linear discriminant (PLDA), and weighted gene co-expression network analysis (WGCNA) models were used to investigate the featured genes/pathways while minimizing the disadvantages of individual methods. During the course of infection, 6,097 and 2,931 DEGs were identified in the head kidney and liver, respectively. Markers of protein processing in the endoplasmic reticulum, oxidative phosphorylation, and the proteasome were highly expressed. Likewise, simultaneous ferroptosis and cellular reconstruction was observed, which is strongly linked to multiple organ dysfunction. In contrast, pathways relevant to cellular replication were up-regulated in only the head kidney, while endocytosis- and phagosome-related pathways were notably expressed in the liver. Moreover, interestingly, most immune-relevant pathways (e.g., leukocyte trans-endothelial migration, Fc gamma R-mediated phagocytosis) were highly activated in the liver, but the same pathways in the head kidney were down-regulated. These conflicting results from different organs suggest that interpretation of co-expression among organs is crucial for profiling of systemic responses during infection. The dual-organ transcriptomics approaches presented in this study will greatly contribute to our understanding of multi-organ interactions under I. multifiliis infection from a broader perspective.
Sujet(s)
Infections à ciliophores/génétique , Maladies des poissons/génétique , Interactions hôte-pathogène/génétique , Hymenostomatida/pathogénicité , Apprentissage machine , Oncorhynchus mykiss/génétique , Oncorhynchus mykiss/parasitologie , Transcriptome , Animaux , Infections à ciliophores/immunologie , Infections à ciliophores/parasitologie , Maladies des poissons/immunologie , Régulation de l'expression des gènes , Réseaux de régulation génique , Branchies/immunologie , Rein céphalique/immunologie , Interactions hôte-pathogène/immunologie , Immunité innée/génétique , Foie/immunologie , Oncorhynchus mykiss/immunologie , RNA-Seq/méthodes , Transduction du signal/génétique , Transduction du signal/immunologie , Virulence/génétique , Virulence/immunologie , Facteurs de virulenceRÉSUMÉ
Sea lice (Caligus rogercresseyi) is an ectoparasite which causes major production losses in the salmon aquaculture industry worldwide. Atlantic salmon (Salmo salar) and rainbow trout (Oncorhynchus mykiss) are two of the most susceptible salmonid species to sea lice infestation. The objectives of this study were to: (1) identify genomic regions associated with resistance to Caligus rogercresseyi in Atlantic salmon and rainbow trout by performing single-step Genome-Wide Association studies (ssGWAS), and (2) identify candidate genes related to trait variation based on exploring orthologous genes within the associated regions across species. A total of 2626 Atlantic salmon and 2643 rainbow trout were challenged and genotyped with 50 K and 57 K SNP panels, respectively. We ran two independent ssGWAS for sea lice resistance on each species and identified 7 and 13 regions explaining more than 1% of the genetic variance for the trait, with the most important regions explaining 3% and 2.7% for Atlantic salmon and rainbow trout, respectively. We identified genes associated with immune response, cytoskeleton function, and cell migration when focusing on important genomic regions for each species. Moreover, we found 15 common orthogroups which were present in more than one associated genomic region, within- or between-species; however, only one orthogroup showed a clear potential biological relevance in the response against sea lice. For instance, dual-specificity protein phosphatase 10-like (dusp10) and dual-specificity protein phosphatase 8 (dusp8) were found in genomic regions associated with lice density in Atlantic salmon and rainbow trout, respectively. Dusp10 and dusp8 are modulators of the MAPK pathway and might be involved in the differences of the inflammation response between lice resistant and susceptible fish from both species. Our results provide further knowledge on candidate genes related to sea lice resistance and may help establish better control for sea lice in fish populations.
Sujet(s)
Oncorhynchus mykiss/génétique , Oncorhynchus mykiss/parasitologie , Phthiraptera/pathogénicité , Saumon/génétique , Saumon/parasitologie , Animaux , Aquaculture/méthodes , Prédisposition aux maladies/microbiologie , Maladies des poissons/génétique , Maladies des poissons/parasitologie , Étude d'association pangénomique/méthodes , Génomique/méthodes , Génotype , Immunité/génétique , Pédiculoses/génétique , Pédiculoses/microbiologie , Phénotype , Salmo salar/génétique , Salmo salar/parasitologieRÉSUMÉ
Herein, data on rainbow trout infections with the copepod Caligus lacustris in cage aquaculture on Lake Ladoga is presented. Caligus lacustris (n = 127 ex.) were collected from a farm in Lake Ladoga housing cage-reared rainbow trout to describe the size-age and sex structure of the copepod population. Morphological features of the copepods were evaluated according to 10 characters with terminology proposed by Kabata and Gusev (J Linn Soc (Zool) 46(309):155-207, 1966). To determine the phylogenetic position of C. lacustris within the genus Caligus, fragments of the cytochrome c oxidase subunit 1 mitochondrial gene (COI, 645 bp) and 18S rRNA gene (1617 bp) were sequenced. An increase of parasite prevalence was observed as the lake was warming up from July to September. The morphological features of the crustacean's larval and adult stages, characterized by specific parameters of quantitative traits, are described. Three COI haplotypes and only one 18S rRNA haplotype of C. lacustris were identified among five samples. Based on 18S rRNA analysis (resolution of the COI tree was poor), we can conclude that the clade containing C. lacustris, and the aforementioned sister species, appears as an early radiation of the genus Caligus. The development of freshwater aquaculture contributes to the transfer of the native parasite C. lacustris to farmed rainbow trout.
Sujet(s)
Copepoda/anatomie et histologie , Copepoda/classification , Oncorhynchus mykiss/parasitologie , Phylogenèse , Animaux , Aquaculture , Copepoda/génétique , Démographie , Maladies des poissons/parasitologie , Maladies des poissons/transmission , Lacs , Parasitoses animales/parasitologie , Parasitoses animales/transmission , ARN ribosomique 18S/génétiqueRÉSUMÉ
Diseases caused by myxozoan parasites represent a significant threat to the health of salmonids in both the wild and aquaculture setting, and there are no effective therapeutants for their control. The myxozoan Ceratonova shasta is an intestinal parasite of salmonids that causes severe enteronecrosis and mortality. Most fish populations appear genetically fixed as resistant or susceptible to the parasite, offering an attractive model system for studying the immune response to myxozoans. We hypothesized that early recognition of the parasite is a critical factor driving resistance and that susceptible fish would have a delayed immune response. RNA-seq was used to identify genes that were differentially expressed in the gills and intestine during the early stages of C. shasta infection in both resistant and susceptible steelhead (Oncorhynchus mykiss). This revealed a downregulation of genes involved in the IFN-γ signaling pathway in the gills of both phenotypes. Despite this, resistant fish quickly contained the infection and several immune genes, including two innate immune receptors were upregulated. Susceptible fish, on the other hand, failed to control parasite proliferation and had no discernible immune response to the parasite, including a near-complete lack of differential gene expression in the intestine. Further sequencing of intestinal samples from susceptible fish during the middle and late stages of infection showed a vigorous yet ineffective immune response driven by IFN-γ, and massive differential expression of genes involved in cell adhesion and the extracellular matrix, which coincided with the breakdown of the intestinal structure. Our results suggest that the parasite may be suppressing the host's immune system during the initial invasion, and that susceptible fish are unable to recognize the parasite invading the intestine or mount an effective immune response. These findings improve our understanding of myxozoan-host interactions while providing a set of putative resistance markers for future studies.
Sujet(s)
Prédisposition génétique à une maladie/génétique , Myxozoa/génétique , Oncorhynchus mykiss/génétique , Animaux , Prédisposition aux maladies/métabolisme , Maladies des poissons/parasitologie , Expression des gènes/génétique , Analyse de profil d'expression de gènes/méthodes , Génomique/méthodes , Branchies/parasitologie , Intestins/parasitologie , Oncorhynchus mykiss/immunologie , Oncorhynchus mykiss/parasitologie , Parasites/génétique , Parasitoses animales/parasitologie , Transcriptome/génétiqueRÉSUMÉ
Proteases and their inhibitors play critical roles in host-parasite interactions and in the outcomes of infections. Ceratonova shasta is a myxozoan pathogen that causes enteronecrosis in economically important salmonids from the Pacific Northwest of North America. This cnidarian parasite has host-specific genotypes with varying virulence, making it a powerful system to decipher virulence mechanisms in myxozoans. Using C. shasta genome and transcriptome, we identified four proteases of different catalytic types: cathepsin D (aspartic), cathepsin L and Z-like (cysteine) and aminopeptidase-N (metallo); and a stefin (cysteine protease inhibitor), which implied involvement in virulence and hence represent target molecules for the development of therapeutic strategies. We characterized, annotated and modelled their 3D protein structure using bioinformatics and computational tools. We quantified their expression in C. shasta genotype 0 (low virulence, no mortality) and IIR (high virulence and mortality) in rainbow trout Oncorhynchus mykiss, to demonstrate that there are major differences between the genotypes during infection and parasite development. High proliferation of genotype IIR was associated with high expression of the cathepsin D and the stefin, likely correlated with high nutrient demands and to regulate cell metabolism, with upregulation preceding massive proliferation and systemic dispersion. In contrast, upregulation of the cathepsin L and Z-like cysteine proteases may have roles in host immune evasion in genotype 0 infections, which are associated with low proliferation, low inflammation and non-destructive development. In contrast to the other proteases, C. shasta aminopeptidase-N appears to have a prominent role in nematocyst formation in both genotypes, but only during sporogenesis. Homology searches of C. shasta proteases against other myxozoan transcriptomes revealed a high abundance of cathepsin L and aminopeptidase homologs suggesting common gene requirements across species. Our study identified molecules of potential therapeutic significance for aquaculture and serves as a baseline for future research aimed at functional characterisation of these targets.
Sujet(s)
Cnidaria , Maladies des poissons , Oncorhynchus mykiss , Parasitoses animales , Animaux , Maladies des poissons/parasitologie , Oncorhynchus mykiss/parasitologie , Peptide hydrolases , VirulenceRÉSUMÉ
With the aim to determine the prevalence and mean parasite intensity in Oncorhynchus mykiss, 120 specimens were analyzed between April and September 2018. The cavity analysis was done by visual inspection, scraping of mucus, and extraction of the branchial arches. In the evisceration process, the intestine, the liver, and the kidney were separated, while the musculature was analyzed using the "candling table" method. All the collected material was preserved in 10% buffered formaldehyde and sent to the Laboratory of Parasitology and Parasitic Diseases, of the Center for Agroveterinary Sciences (CAV) of the University of the State of Santa Catarina (UDESC) for making the slides and identifying the parasites. Parasites were detected only in the analysis of the scraping of body mucus. Only specimens of the genus Trichodina were identified, in 34 of the 120 fish analyzed, in two collections, resulting in a prevalence of 28.33%. In total, 144 specimens of Trichodina were observed. The overall mean intensity was of 4.24 parasites in each fish analyzed. Characteristic lesions of infection by protozoa were not identified. This is the first report of the occurrence of Trichodina spp. in O. mykiss bred in an intensive system in Brazil, with low rates of parasitic infection in the mountain region of Santa Catarina.(AU)
Sujet(s)
Animaux , Oligohymenophorea , Infections à ciliophores/médecine vétérinaire , Oncorhynchus mykiss/parasitologie , BrésilRÉSUMÉ
The parasitic ciliate Ichthyophthirius multifiliis has a low host specificity eliciting white spot disease (WSD) in a wide range of freshwater fishes worldwide. The parasite multiplies rapidly whereby the infection may reach problematic levels in a host population within a few days. The parasite targets both wild and cultured fish but the huge economic impact of the protozoan is associated with mortality, morbidity and treatment in aquacultural enterprises. We have investigated the potential for genetic selection of WSD-resistant strains of rainbow trout. Applying the DNA typing system Affymetrix® and characterizing the genome of the individual fish by use of 57,501 single nucleotide polymorphisms (SNP) and their location on the rainbow trout chromosomes, we have genetically characterized rainbow trout with different levels of natural resistance towards WSD. Quantitative trait loci (QTL) used for the selection of breeders with specific markers for resistance are reported. We found a significant association between resistance towards I. multifiliis infection and SNP markers located on the two specific rainbow trout chromosomes Omy 16 and Omy 17. Comparing the expression of immune-related genes in fish-with and without clinical signs-we recorded no significant difference. However, trout surviving the infection showed high expression levels of genes encoding IgT, T-cell receptor TCRß, C3, cathelicidins 1 and 2 and SAA, suggesting these genes to be associated with protection.
Sujet(s)
Maladies des poissons/parasitologie , Hymenostomatida , Oncorhynchus mykiss/génétique , Oncorhynchus mykiss/parasitologie , Locus de caractère quantitatif , Animaux , Aquaculture , Infections à ciliophores/immunologie , Infections à ciliophores/médecine vétérinaire , Régulation de l'expression des gènes/immunologie , Génome , Immunité innée/génétique , Oncorhynchus mykiss/immunologie , Polymorphisme de nucléotide simple , Reproduction sélective/génétiqueRÉSUMÉ
Tetracapsuloides bryosalmonae (Myxozoa: Malacosporea) is the causative agent of proliferative kidney disease (PKD), which affects both wild and farmed salmonid fish. The objective of this study was to outline differences in susceptibility to PKD in different salmonid species, hybrids and breeding lineages. Susceptibility to T. bryosalmonae infection was established based on cumulative mortality, pathological findings and detection of T. bryosalmonae in the kidney using immunohistochemistry and molecular methods. Determination of pure and hybrid individuals of different species in the genus Salvelinus, and dissimilarity of rainbow trout lineages, was performed using traditional polymerase chain reaction (PCR) and microsatellite analyses. Rainbow trout displayed higher disease severity compared with brook trout and Alsatian charr. Moreover, the results indicated differences in infection susceptibility, not only among different salmonid species but also among different lineages of charr and rainbow trout. Our study indicated that some salmonid species and even different lineages of the same species are more suitable for farming under PKD pressure.
Sujet(s)
Maladies des poissons/anatomopathologie , Maladies du rein/anatomopathologie , Myxozoa/pathogénicité , Parasitoses animales/anatomopathologie , Truite/parasitologie , Animaux , Aquaculture , République tchèque , Immunohistochimie/médecine vétérinaire , Répétitions microsatellites , Myxozoa/génétique , Oncorhynchus mykiss/parasitologie , Réaction de polymérisation en chaîne/médecine vétérinaireRÉSUMÉ
Salmincola californiensis is a Lernaeopodid copepod parasitizing Pacific salmon and trout of the genus Oncorhynchus. Salmincola californiensis is of increasing concern in both native and introduced ranges because of its potential fish health impacts and high infection prevalence and intensity in some systems. Discrepancies in the documented life history phenology of S. californiensis with the sister species Salmincola edwardsii, as well as our laboratory observations, led us to question the existing literature. We documented a naupliar stage, thought lost for S. californiensis. In addition, we found a high degree of thermal sensitivity in egg development, with eggs developing faster under warmer conditions. Survival of copepodids was also highly dependent on temperature, with warmer conditions reducing lifespan. The longest lived copepodid survived 18 days at 4°C in stark contrast to the generally accepted <48 h survival for that life stage. We also note a consistent relationship between egg sac size and the number of eggs contained. However, egg sac sizes were highly variable. Our findings demonstrate that revisiting old assumptions for S. californiensis and related taxa will be a necessary step to improving our knowledge of the parasite life history and development that will be critical to disease management.
Sujet(s)
Copepoda , Étapes du cycle de vie/physiologie , Salmonidae/parasitologie , Animaux , Copepoda/croissance et développement , Copepoda/physiologie , Ectoparasitoses/médecine vétérinaire , Maladies des poissons/parasitologie , Branchies/parasitologie , Oncorhynchus mykiss/parasitologie , Saumon/parasitologie , TempératureRÉSUMÉ
Proliferative kidney disease (PKD) caused by the myxozoan parasite Tetracapsuloides bryosalmonae is one of the most serious infectious diseases negatively impacting farmed and wild salmonids throughout Europe and North America. PKD pathogenesis results in a massive B cell proliferation and dysregulation with aberrant immunoglobulin production and plasma cell differentiation along with a decrease in myeloid cells and inhibition of innate pathways. Despite the huge immunopathological reaction in the kidney during infection, under specific conditions, fish can survive and return to full fitness. Fish are unique in this ability to recover renal structure and functionality from extensive tissue damage in contrast to mammals. However, only limited knowledge exists regarding the host immune response coinciding with PKD recovery. Moreover, almost no studies of the immune response during disease recovery exist in fish. We utilized the rainbow trout-T. bryosalmonae system as an immunological model of disease recovery. Our results demonstrated that recovery is preceded by an intense immune response at the transcript level, decreasing parasite burden, and an increased degree of kidney inflammation. Later in the recovery phase, the immune response transpired with a significant decrease in lymphocytes and an increase in myeloid cells. These lymphocytes populations contained lower levels of B cells comparative to the control in the anterior and posterior kidney. Additionally, there was downregulation of several transcripts used as markers for plasma cells (blimp1, igt sec, igm sec, igd sec, and cd38) and T cell subsets (cd4, cd8α, cd8ß, and tcrß). The decrease in these T cell transcripts significantly correlated with decreasing parasite intensity. Alternatively, there was strong upregulation of pax-5 and igt mem. This suggests a change in B cell processes during the recovery phase relative to clinical PKD may be necessary for the host to re-establish homeostasis in terms of an arrest in the dominant antibody like response transitioning to a transcriptional profile associated with resting B cells. The knowledge generated here in combination with earlier studies illuminates the full power of analyzing the entire trajectory of disease from the normal healthy state to recovery enabling the measurement of an immune response to pinpoint a specific disease stage.
Sujet(s)
Lymphocytes B/immunologie , Maladies des poissons/immunologie , Oncorhynchus mykiss/immunologie , Oncorhynchus mykiss/parasitologie , Parasitoses animales/immunologie , Lymphocytes T/immunologie , Animaux , Maladies des poissons/parasitologie , Maladies du rein/immunologie , Maladies du rein/médecine vétérinaire , Myxozoa/immunologieRÉSUMÉ
There are differences in disease susceptibility to whirling disease (WD) among strains of rainbow trout. The North American strain Trout Lodge (TL) is highly susceptible, whereas the German Hofer (HO) strain is more resistant. The suppressor of cytokine signaling (SOCS) proteins are key in inhibiting cytokine signaling. Their role in modulating the immune response against whirling disease is not completely clear. This study aimed at investigating the transcriptional response of SOCS1 and SOCS3 genes to Myxobolus cerebralis along with that of several upstream regulators and immune response genes. M. cerebralis induced the expression of SOCS1, the IL-6-dependent SOCS3, the anti-inflammatory cytokine IL-10 and the Treg associated transcription factor FOXP3 in TL fish at multiple time points, which likely caused a restricted STAT1 and STAT3 activity affecting the Th17/Treg17 balance. The expression of SOCS1 and the IL-6-dependent SOCS3 was induced constraining the activation of STAT1 and STAT3 in TL fish, thereby causing Th17/Treg17 imbalance and leaving the fish unable to establish a protective immune response against M. cerebralis or control inflammatory reactions increasing susceptibility to WD. Conversely, in HO fish, the expression of SOCS1 and SOCS3 was restrained, whereas the expression of STAT1 and IL-23-mediated STAT3 was induced potentially enabling more controlled immune responses, accelerating parasite clearance and elevating resistance. The induced expression of STAT1 and IL-23-mediated STAT3 likely maintained a successful Th17/Treg17 balance and enabled fish to promote effective immune responses favouring resistance against WD. The results provide insights into the role of SOCS1 and SOCS3 in regulating the activation and magnitude of host immunity in rainbow trout, which may help us understand the mechanisms that underlie the variation in resistance to WD.
Sujet(s)
Prédisposition aux maladies/immunologie , Maladies des poissons/immunologie , Myxobolus/immunologie , Oncorhynchus mykiss/immunologie , Parasitoses animales/immunologie , Facteur de transcription STAT-3/immunologie , Protéine-3 suppressive de la signalisation des cytokine/immunologie , Animaux , Oncorhynchus mykiss/parasitologie , Facteur de transcription STAT-1/immunologie , Protéine-1 suppressive de la signalisation des cytokines/immunologie , Lymphocytes T régulateurs/cytologie , Lymphocytes T régulateurs/immunologie , Cellules Th17/cytologie , Cellules Th17/immunologieRÉSUMÉ
The interaction of pathogens between wild and farmed aquatic animal populations is a concern that remains unclear and controversial. Ichthyophthirius multifiliis, a ciliated protozoan parasite, is a pathogen of freshwater finfish species with geographic and host range that causes significant economic losses in aquaculture. Flow-through farming systems may facilitate the transfer of such a parasite with free-living stages between farmed and wild stocks. Here, experimental and field study infection data are used to describe the infection dynamics of Ichthyophthirius multifiliis in rainbow trout using a simple macroparasite model by including host resistance. The study considered flow-through farming systems with a single or two age-class compartments and simulated the transfer of the parasite between farmed and wild fish populations. Results suggest that aquaculture can promote the prevalence of the resistance in wild stocks by increasing the parasite population in the wild environment. At the same time, acquired resistance in the farmed fish population may protect the wild fish population from lethal effects of the parasite by reducing the total parasite population. This study offers a promising mathematical basis for understanding the effects of freshwater aquaculture in disease spread in wildlife, developing risk assessment modeling, and exploring new ways of aquaculture management.