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| 2. |
- Jönsson, K. Ingemar, 1959-, et al.
(author)
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On the disparate terminological use of the concept cryptobiosis
- 2004
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In: Journal of Fish Diseases. - : Wiley-Blackwell. - 0140-7775 .- 1365-2761. ; 27:3, s. 175-176
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Journal article (peer-reviewed)abstract
- Conceptual and terminological consistency is an important component of science, promoting clarity and preventing confusion. Scientists should therefore always try to avoid giving different meanings to the same term. Apart from this general aspect, multiple definitions of a single term also give rise to practical problems, particularly in connection with literature search. In this note, I will bring attention to a term, cryptobiosis, that has relatively recently appeared in the field of fish disease research, but which has a much longer history and use in a completely different area.The concept of cryptobiosis was introduced by Keilin (1959) and defined as ‘the state of an organism when it shows no visible signs of life and when its metabolic activity becomes hardly measurable, or comes reversibly to a standstill’ (Keilin 1959, p. 166). Cryptobiosis replaced the earlier term anabiosis, and is today generally accepted as the common term for different ametabolic life forms (e.g. Clegg 2001; Wright 2001). Cryptobiosis means ‘hidden life’, an appropriate name for a state in which all traditional attributes of life (metabolism, reproduction, DNA replication) are absent. Cryptobiotic life forms have been documented in a variety of organisms, including both plants and animals, but in the latter category mainly among invertebrates (Wright, Westh & Ramløv 1992). Cryptobiosis is commonly induced by desiccation (so-called anhydrobiosis; e.g. Keilin 1959; Jönsson 2001), and aquatic invertebrates such as rotifers, nematodes and tardigrades living in microhabitats exposed to rapid desiccation frequently enter a cryptobiotic state. The research field dealing with cryptobiotic, sensu ametabolic, life forms has expanded considerably during the last 30 years, to a large extent fuelled by the detection of the ability of the disaccharide trehalose to protect dry and frozen biological cells (Crowe 2002).More recently, a completely different use of the term cryptobiosis has appeared in the literature on fish disease. In this literature, the term refers to infections of fish by biflagellated protozoa of the genus Cryptobia. Because of the economic importance of salmonid fish, much of the Cryptobia research has focused on Cryptobia salmositica (Katz) that infects salmonids (Woo 2001). The origin of the term cryptobiosis within fish pathology and studies of Cryptobia is unclear, but the earliest record of the term that I have found is Obradovic & Fijan (1979) who used it in a paper on chemotherapeutic treatment against Cryptobia in carp. From 1987 onwards, Woo et al. have used the term frequently (e.g. Woo, Leatherland & Lee 1987; Woo 1987, 1998, 2001), but apparently without any comments on the original proposal of the term. Curiously, few other researchers on Cryptobia seem to have adopted the cryptobiosis terminology, at least as judged from an examination of published titles. Other authors have instead used the expression ‘infections by Cryptobia’. Although using cryptobiosis as a term for infections by Cryptobia is consistent with the rule of creating names for infectious diseases by putting -osis as a post-fix to the name of the infecting organism, in the current case it creates terminological confusion.The problems of using the term cryptobiosis in several unrelated fields are obvious. A title such as ‘The biology of cryptobiosis’ would attract the attention of many students interested in ametabolic life forms. They would be disappointed, however, if the paper turned out to be about Cryptobia infection biology. Similarly, fish biologists would find the publication irrelevant to their research if it were properly confined to ametabolic life forms.Because ‘cryptobiosis’ as a term for ametabolic life forms is well established and has been used for more than 40 years, it should have priority over the more recent and limited use within fish pathology. I therefore hope that fish pathologists will avoid using the term cryptobiosis and instead use ‘infections by Cryptobia’, ‘cryptobiasis’ or some other term that does not interfere with already established terminology.
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| 3. |
- Jutfelt, Fredrik, 1975, et al.
(author)
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Translocation of viable Aeromonas salmonicida across the intestine of rainbow trout, Oncorhynchus mykiss (Walbaum)
- 2006
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In: Journal of Fish Diseases. - : Wiley. - 0140-7775 .- 1365-2761. ; 29:5, s. 255-262
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Journal article (peer-reviewed)abstract
- The pathogenic bacterium Aeromonas salmonicida is the causative agent of the destructive disease furunculosis in salmonids. Horizontal transmission in salmonids has been suggested to occur via the skin, gills and/or intestine. Previous reports are contradictory regarding the role of the intestine as a route of infection. The present study therefore investigates the possibility of bacterial translocation across intestinal epithelia using Ussing chamber technology, in vitro. Intestinal segments were exposed for 90 min to fluorescein isothiocyanate-labelled pathogenic A. salmonicida. Sampling from the serosal side of the Ussing chambers showed that bacteria were able to translocate across the intestinal epithelium in both the proximal and distal regions. Plating and subsequent colony counting showed that the bacteria were viable after translocation. During the 90 min exposure to A. salmonicida, the intestinal segments maintained high viability as measured by electrical parameters. The distal region responded to bacterial exposure by increasing the electrical resistance, indicating an increased mucus secretion. This study thus demonstrates translocation of live A. salmonicida through the intestinal epithelium of rainbow trout, suggesting that the intestine is a possible route of infection in salmonids.
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| 4. |
- Kallert, D. M., et al.
(author)
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The life cycle of Henneguya nuesslini Schuberg & Schroder, 1905 (Myxozoa) involves a triactinomyxon-type actinospore
- 2005
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In: Journal of Fish Diseases. - : Wiley. - 0140-7775 .- 1365-2761. ; 28:2, s. 71-79
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Journal article (peer-reviewed)abstract
- The life cycle of the histozoic myxozoan parasite Henneguya nuesslini was investigated in two salmonid host species. Naive brown trout, Salmo trutta, and brook trout, Salvelinus fontinalis, were experimentally infected in two trials by triactinomyxon type actinospores from naturally infected Tubifex tubifex. In exposed common carp, Cyprinus carpio, no myxospore production was detected. The parasite formed cysts with mature myxospores in the connective tissue of the fish 102 days postexposure. The morphology of both actinosporean and myxosporean stages was described by light microscopy and a 1417-bp fragment of the 18S rDNA gene was sequenced. Sequence analysis confirmed the absolute congruence of the two developmental stages and assisted in determining species identity. Host range, tissue specificity and myxospore measurements provided sufficiently distinctive features to confirm species validity and were thus crucial for identification. The triactinomyxon spores had 16 secondary germ cells, unique dimensions, a very opaque sporoplasm matrix and three conspicuously protruding, pyriform polar capsules. This is the first record of a Henneguya sp. life cycle with a triactinomyxon-type actinospore, which suggests a close relationship with the Myxobolus group and a polyphyletic origin of the genus Henneguya.
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| 5. |
- Lilley, J H, et al.
(author)
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Molecular characterization of the fish-pathogenic fungus Aphanomyces invadans.
- 2003
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In: Journal of Fish Diseases. - : Wiley. - 0140-7775 .- 1365-2761. ; 26:5, s. 263-75
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Journal article (peer-reviewed)abstract
- Aphanomyces invadans (Saprolegniaceae) is a peronosporomycete fungus associated with the serious fish disease, epizootic ulcerative syndrome (EUS), also known as mycotic granulomatosis. In this study, interspecific relationships were examined between A. invadans isolates and other aquatic animal pathogenic Saprolegniaceae, and saprophytic Saprolegniaceae from EUS-affected areas. Restriction fragment length polymorphisms and sequences of ribosomal DNA confirmed that A. invadans is distinct from all other species studied. A sequence from the internal transcribed spacer region ITS1, unique to A. invadans, was used to design primers for a PCR-based diagnostic test. Intraspecific relationships were also examined by random amplification of polymorphic DNA using 20 isolates of A. invadans from six countries. The isolates showed a high degree of genetic homogeneity using 14 random ten-mer primers. This provides evidence that the fungus has spread across Asia in one relatively rapid episode, which is consistent with reports of outbreaks of EUS. Physiological distinctions between A. invadans and other Aphanomyces species based on a data set of 16 growth parameters showed remarkable taxonomic congruence with the molecular phylogeny.
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| 8. |
- Frainer, André
(author)
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Effects of fish species composition on Diphyllobothrium spp. infections in brown trout - is three-spined stickleback a key species?
- 2016
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In: Journal of Fish Diseases. - : Wiley. - 0140-7775 .- 1365-2761. ; 39, s. 1313-1323
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Journal article (peer-reviewed)abstract
- Subarctic populations of brown trout (Salmo trutta) are often heavily infected with cestodes of the genus Diphyllobothrium, assumedly because of their piscivorous behaviour. This study explores possible associations between availability of fish prey and Diphyllobothrium spp. infections in lacustrine trout populations. Trout in (i) allopatry (group T); (ii) sympatry with Arctic charr (Salvelinus alpinus) (group TC); and (iii) sympatry with charr and three-spined stickleback (Gasterosteus aculeatus) (group TCS) were contrasted. Mean abundance and intensity of Diphyllobothrium spp. were higher in group TCS compared to groups TC and T. Prevalence, however, was similarly higher in groups TCS and TC compared to group T. Zero-altered negative binomial modelling identified the lowest probability of infection in group T and similar probabilities of infection in groups TC and TCS, whereas the highest intensity was predicted in group TCS. The most infected trout were from the group co-occurring with stickleback (TCS), possibly due to a higher availability of fish prey. In conclusion, our study demonstrates elevated Diphyllobothrium spp. infections in lacustrine trout populations where fish prey are available and suggests that highly available and easily caught stickleback prey may play a key role in the transmission of Diphyllobothrium spp. parasite larvae.
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| 10. |
- Myrenås, Elin, et al.
(author)
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Effects of the invasive swim bladder parasite Anguillicola crassus on health and condition indicators in the European eel
- 2023
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In: Journal of Fish Diseases. - 0140-7775 .- 1365-2761. ; 46, s. 1029-1047
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Journal article (peer-reviewed)abstract
- Parasites negatively affect biological processes within their hosts, which may alter for example health, growth, and reproductive ability. Non-native invasive parasites, in particular, may have large effects on the endemic hosts, given that the hosts lack evolved specific defences against such parasites. The swim bladder nematode Anguillicola crassus, an invasive parasite originating from Asia, is found in the European eel (Anguilla anguilla, L. 1758), since the 1980s. We investigated whether A. crassus affected several indicators related to health of the European eel (spleen- and liver size, body fat content and relative condition). Our results indicate that during the continental residency of the eels, infection by A. crassus had no major negative impacts on the investigated health indicators at the generally low infection intensities present in this study (median 2-3 visible parasites). Given that many of the adult eels were found to have swim bladder damage, concerns about their spawning migration through deeper oceanic environments can still be raised. To allow further investigations, we suggest that quantification of swim bladder damage should be implemented in eel-monitoring programs. Compared to other parasite pressure parameters, swim bladder damage provides additional information about past infections and future problems.
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| 11. |
- Schwenteit, J. M., et al.
(author)
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Construction of Aeromonas salmonicida subsp. achromogenes AsaP1-toxoid strains and study of their ability to induce immunity in Arctic char, Salvelinus alpinus L.
- 2015
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In: Journal of Fish Diseases. - : Wiley. - 0140-7775 .- 1365-2761. ; 38:10, s. 891-900
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Journal article (peer-reviewed)abstract
- The metalloendopeptidase AsaP1 is one of the major extracellular virulence factors of A. salmonicida subsp. achromogenes, expressed as a 37-kDa pre-pro-peptide and processed to a 19-kDa active peptide. The aim of this study was to construct mutant strains secreting an AsaP1-toxoid instead of AsaP1-wt, to study virulence of these strains and to test the potency of the AsaP1-toxoid bacterin and the recombinant AsaP1-toxoids to induce protective immunity in Arctic char. Two A. salmonicida mutants were constructed that secrete either AsaP1(E294A) or AsaP1(Y309F). The secreted AsaP1(Y309F)-toxoid had weak caseinolytic activity and was processed to the 19-kDa peptide, whereas the AsaP1(E294A)-toxoid was found as a 37-kDa pre-pro-peptide suggesting that AsaP1 is auto-catalytically processed. The LD50 of the AsaP1(Y309F)-toxoid mutant in Arctic char was significantly higher than that of the corresponding wt strain, and LD50 of the AsaP1(E294A)-toxoid mutant was comparable with that of an AsaP1-deficient strain. Bacterin based on AsaP1(Y309F)-toxoid mutant provided significant protection, comparable with that induced by a commercial polyvalent furunculosis vaccine. Detoxification of AsaP1 is very hard, expensive and time consuming. Therefore, an AsaP1-toxoid-secreting mutant is more suitable than the respective wt strain for production of fish bacterins aimed to protect against atypical furunculosis.
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| 14. |
- Sundh, Henrik, 1976, et al.
(author)
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The effect of hyperoxygenation and reduced flow in fresh water and subsequent infectious pancreatic necrosis virus challenge in sea water, on the intestinal barrier integrity in Atlantic salmon, Salmo salar L
- 2009
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In: Journal of Fish Diseases. - 1365-2761. ; 32:8, s. 687-98
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Journal article (peer-reviewed)abstract
- In high intensive fish production systems, hyperoxygenation and reduced flow are often used to save water and increase the holding capacity. This commonly used husbandry practice has been shown to be stressful to fish and increase mortality after infectious pancreatic necrosis virus (IPNV) challenge, but the cause and effect relationship is not known. Salmonids are particularly sensitive to stress during smoltification and the first weeks after seawater (SW) transfer. This work aimed at investigating the impact of hyperoxygenation combined with reduced flow in fresh water (FW), on the intestinal barrier in FW as well as during later life stages in SW. It further aims at investigating the role of the intestinal barrier during IPNV challenge and possible secondary infections. Hyperoxygenation in FW acted as a stressor as shown by significantly elevated plasma cortisol levels. This stressful husbandry condition tended to increase paracellular permeability (P(app)) as well as translocation of Aeromonas salmonicida in the posterior intestine of Atlantic salmon. After transfer to SW and subsequent IPNV challenge, intestinal permeability, as shown by P(app), and translocation rate of A. salmonicida increased in the anterior intestine, concomitant with further elevation in plasma cortisol levels. In the anterior intestine, four of five fish displayed alterations in intestinal appearance. In two of five fish, IPNV caused massive necrosis with significant loss of cell material and in a further two fish, IPNV caused increased infiltration of lymphocytes into the epithelium and granulocytes in the lamina propria. Hyperoxygenation and reduced flow in the FW stage may serve as stressors with impact mainly during later stages of development. Fish with an early history of hyperoxygenation showed a higher stress response concomitant with a disturbed intestinal barrier function, which may be a cause for the increased susceptibility to IPNV infection and increased susceptibility to secondary infections.
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| 15. |
- Vasemägi, Anti
(author)
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Climate change-driven disease in sympatric hosts: Temporal dynamics of parasite burden and proliferative kidney disease in wild brown trout and Atlantic salmon
- 2021
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In: Journal of Fish Diseases. - : Wiley. - 0140-7775 .- 1365-2761. ; 44, s. 689-699
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Journal article (peer-reviewed)abstract
- Global climate change is altering the abundance and spread of various parasites, which has important consequences not only for host-parasite interactions but also for the relationships between different host species. Here, we focus on the myxozoan endoparasite Tetracapsuloides bryosalmonae that causes temperature-dependent proliferative kidney disease (PKD) in salmonids. We characterized the temporal changes in the parasite load and the severity of PKD signs (renal hyperplasia, haematocrit) in two sympatric populations of wild brown trout (Salmo trutta) and Atlantic salmon (Salmo salar). We found that both the parasite load and disease signs vary considerably between individuals, species, rivers and sampling periods. We showed that Atlantic salmon was able to slow down the initial parasite proliferation rate and subsequently tolerate high parasite burden without obvious disease signs. In contrast, the initial parasite proliferation rate was much higher in brown trout, which was followed by the development of severe PKD signs. Thus, the speed of parasite proliferation, rather than the absolute number of the parasites in the host kidney, may play an important role in interspecific variation in PKD susceptibility. To conclude, this study illustrates the usefulness of temporal perspective for understanding host defence mechanisms and climate change-mediated impacts in the wild.
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| 16. |
- Weichert, Fabian, et al.
(author)
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A multi-biomarker study on Atlantic salmon (Salmo salar L.) affected by the emerging Red Skin Disease in the Baltic Sea
- 2021
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In: Journal of Fish Diseases. - : Wiley. - 0140-7775 .- 1365-2761. ; 44:4, s. 429-440
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Journal article (peer-reviewed)abstract
- For half a decade, the Atlantic salmon in the Baltic Sea has been facing severe health issues. Clinical signs like haemorrhage, erosions and ulcerative/necrotic skin conditions in returning adults have been reported from different Swedish rivers. These primary disease signs precede a secondary, terminal fungal infection. As initial investigations of the disease did not provide conclusive answers regarding the pathogenesis, this study was initiated to gain insight into a possible link between this so-called Red Skin Disease and anthropogenic influences. Therefore, returning salmon were caught in rivers along the Swedish coast and different tissues were sampled. The focus was put on the measurements of a battery of biomarkers as well as biochemical and haematological parameters, which were analysed using multivariate statistics. The main findings were a severe osmotic haemodilution, an immune response and an alteration of the carbohydrate metabolism in diseased fish. Furthermore, oxidative stress does not seem to be a likely factor in the pathogenesis. Concluding, certain changes in physiological parameters were shown to be indicative for the disease patterns, while others were ruled out as significant factors. Thus, this study contributes to the understanding of the Red Skin Disease and may act as a hypothesis generator for future studies.
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