Publications by authors named "Kurt Buchmann"

103 Publications

Whole-genome association study searching for QTL for Aeromonas salmonicida resistance in rainbow trout.

Sci Rep 2021 Sep 8;11(1):17857. Epub 2021 Sep 8.

Laboratory of Aquatic Pathobiology, Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C., Copenhagen, Denmark.

Aeromonas salmonicida subsp. salmonicida, the causative agent of furunculosis, has extensive negative effects on wild and farmed salmonids worldwide. Vaccination induces some protection under certain conditions but disease outbreaks occur even in vaccinated fish. Therefore, alternative disease control approaches are required to ensure the sustainable expansion of rainbow trout aquaculture. Selective breeding can be applied to enhance host resistance to pathogens. The present work used genome-wide association study (GWAS) to identify quantitative trait loci (QTL) associated with A. salmonicida resistance in rainbow trout. A total 798 rainbow trout exposed to A. salmonicida by bath challenge revealed 614 susceptible and 138 resistant fish. Genotyping was conducted using the 57 K single nucleotide polymorphism (SNP) array and the GWAS was performed for survival and time to death phenotypes. We identified a QTL on chromosome 16 and located positional candidate genes in the proximity of the most significant SNPs. In addition, samples from exposed fish were examined for expression of 24 immune-relevant genes indicating a systematic immune response to the infection. The present work demonstrated that resistance to A. salmonicida is moderately heritable with oligogenic architecture. These result will be useful for the future breeding programs for improving the natural resistance of rainbow trout against furunculosis.
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http://dx.doi.org/10.1038/s41598-021-97437-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8426485PMC
September 2021

Evidence of IgE-Mediated Cross-Reactions between and Proteins.

Pathogens 2021 Jul 28;10(8). Epub 2021 Jul 28.

Laboratory of Aquatic Pathobiology, Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, 1870 Frederiksberg C, Denmark.

Fish consumers may develop allergic reactions following the ingestion of fish products containing nematode larvae within the genus . Sensitized patients may cross-react with proteins from insects, mites and mollusks, leading to allergic reactions even in the absence of the offending food. Potential cross-reactivity in -allergic patients with larval proteins from other zoonotic parasites present in freshwater and sea fish should be investigated due to an increasing occurrence in certain fish stocks, particularly . In this work, we evaluated IgE-cross reactions by in vivo (skin prick tests with parasites extracts) and in vitro methods (IgE-ELISA and IgE-immunoblot). In vivo skin prick tests (SPT) proved the reactivity of -sensitized patients when exposed to antigens. Sera from -sensitized patients confirmed the reaction with somatic antigens (SA) and excretory/secretory proteins (ES) from . Only anecdotal responses were obtained from other freshwater worm parasites. Consequently, it is suggested that -sensitized humans, especially patients with high levels of specific anti- antibodies, may react to proteins, possibly due to IgE-mediated cross-reactivity.
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http://dx.doi.org/10.3390/pathogens10080950DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8399947PMC
July 2021

Morphological and molecular identification of Cryptocotyle lingua metacercariae isolated from Atlantic cod (Gadus morhua) from Danish seas and whiting (Merlangius merlangus) from the English Channel.

Parasitol Res 2021 Aug 27. Epub 2021 Aug 27.

Laboratory of Aquatic Pathobiology, Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C, Denmark.

Trematode larvae (metacercariae) causing black spot disease occur frequently in gills, fins, skin and the superficial muscle layers of marine fish. Species within the genus Cryptocotyle Lühe, 1899 are frequently associated with this disease. Descriptions of the metacercarial stage are relatively limited and none has hitherto been reported from fish from the English Channel. The present study reports the morphological and molecular identifications of encysted black spot-inducing parasites from whiting (Merlangius merlangus) and Atlantic cod (Gadus morhua) caught respectively from the north coast of France (English Channel) and from Danish sea waters. Metacercariae were characterised morphologically based on microscopic observations and molecularly using Sanger sequencing of fragments of the mitochondrial cox1 gene and rDNA ITS region. Morphological data were compared with available data in the literature. Phylogenetic trees including reference sequences were built to confirm morphological and molecular identifications. This survey constitutes the first description of C. lingua metacercariae in the English Channel ecosystems.
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http://dx.doi.org/10.1007/s00436-021-07278-6DOI Listing
August 2021

Inflammatory reactions in rainbow trout fins and gills exposed to biocides.

Dis Aquat Organ 2021 Aug 26;146:9-21. Epub 2021 Aug 26.

Laboratory of Aquatic Pathobiology, Faculty of Health and Medical Sciences, University of Copenhagen, 1870 Frederiksberg C., Denmark.

Several biocides are widely used in rainbow trout aquaculture against various ectoparasites and ectobionts, but the inflammation induced in treated fish is less well described. Dose-response studies were conducted to elucidate the effects on rainbow trout (gills and fins) induced by a series of biocides including formalin, hydrogen peroxide (H2O2), peracetic acid (PAA) and the surfactant SPH6, which was isolated from the bacterium Pseudomonas H6. The compounds have documented antiparasitic effects, but the specific effects on fish needs further documentation. This study was performed over 24 h, and inflammatory reactions were evaluated in gills and fins. A dose-dependent effect was noted for expression of immune genes encoding for IL-1β, TNFα, IFNγ, IL-10, IL-8, lysozyme, serum amyloid A (SAA), hepcidin, precerebellin and complement factor C3. PAA induced the strongest upregulation of cytokine and acute phase reactant genes followed by H2O2 and formalin. SPH6 showed a lower effect, and in several cases the compound induced downregulation of several genes. Gills showed a stronger response compared to fins. The mucous cell density in fins showed a range of changes which varied by compound. PAA, and to a lesser degree H2O2 and formalin, initially induced mucous cell hyperplasia, whereas SPH6 immediately decreased the number of cells containing mucus.
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http://dx.doi.org/10.3354/dao03617DOI Listing
August 2021

Cercarial Dermatitis at Public Bathing Sites (Region Zealand, Denmark): A Case Series and Literature Review.

Case Rep Dermatol 2021 May-Aug;13(2):360-365. Epub 2021 Jul 16.

Department of Veterinary and Animal Sciences, Laboratory of Aquatic Pathobiology, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg, Denmark.

During recent years, we have observed an increasing occurrence of cercarial dermatitis in Denmark. We here describe 5 new cases from 2019 to 2020 associated with bathing in lakes Esrum sø, Furesø, and Ringen with emphasis on clinical symptoms and their relation to previous exposure to bird schistosome cercariae. In 2020, 2 patients from Furesø suffered from different severity of clinical symptoms after morning bathing in the same lake. We suggest that the differential symptoms may be explained by primary versus secondary exposure to the immunogenic pathogen.
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http://dx.doi.org/10.1159/000516981DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8339491PMC
July 2021

Immersion vaccines against Yersinia ruckeri infection in rainbow trout: Comparative effects of strain differences.

J Fish Dis 2021 Aug 15. Epub 2021 Aug 15.

Laboratory of Aquatic Pathobiology, Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.

The protective effects of autogenous and commercial ERM immersion vaccines (bacterins based on Yersinia ruckeri, serotype O1, biotypes 1 and 2) for rainbow trout (Oncorhynchus mykiss) were compared in order to evaluate whether the use of local pathogen strains for immunization can improve protection. In addition, the effect of the bacterin concentration was established for the commercial product. Following sublethal challenge of vaccinated and non-vaccinated control fish with live bacteria, we followed the bacterial count in the fish (gills, liver and spleen). The expression of genes encoding immune factors (IL-1β, IL-6, IL-8, IL-10, IFN-γ, MHCI, MHCII, CD4, CD8, TCRβ, IgM, IgT, IgD, cathelicidins 1 and 2, SAA and C3) and densities of immune cells in organs were recorded. Both vaccines conferred protection as judged from the reduced bacterial load in exposed fish. Innate immune genes were upregulated in all groups following bacterial challenge but significantly more in non-vaccinated naive fish in which densities of SAA-positive immune cells increased. Immunoglobulin genes were upregulated on day 5 post-challenge, and fish vaccinated with the high commercial bacterin dosage showed increased IgM levels by ELISA on day 14 post-challenge, reflecting that the vaccine dosage was correlated to protection. In conclusion, both vaccine types offered protection to rainbow trout when exposed to live Y. ruckeri and no significant difference between commercial and autogenous vaccines was established.
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http://dx.doi.org/10.1111/jfd.13507DOI Listing
August 2021

Optimization of tools for the detection and identification of Cryptocotyle metacercariae in fish: Digestion method and viability studies.

J Fish Dis 2021 Jul 21. Epub 2021 Jul 21.

ANSES, Laboratory for Food Safety, Boulogne-sur-Mer, France.

Some trematode metacercariae, including marine digeneans belonging to the genus Cryptocotyle, induce black spots in target tissues due to the attraction of fish host melanophores. To promote precise quantification of infection, the counting of black spots has to be confirmed by reliable quantification of metacercariae after tissue digestion. This process ensures the isolation of undamaged parasites for morphological and molecular identification. The aim of this work was to optimize the pepsin digestion protocol and to assess the duration of viability of Cryptocotyle metacercariae in fish post-mortem (pm). Four digestion protocols were compared by measuring the viability rate of metacercariae. The present study shows that the orbital digestion method was the least destructive for metacercariae and allowed better quantification of Cryptocotyle infection. Moreover, morphological identification seemed reliable up to 8 days pm for Cryptocotyle infection.
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http://dx.doi.org/10.1111/jfd.13495DOI Listing
July 2021

Eye fluke effects on Danish freshwater fish: Field and experimental investigations.

J Fish Dis 2021 Jul 21. Epub 2021 Jul 21.

Laboratory of Aquatic Pathobiology, Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C, Denmark.

Eye flukes in fish are common in freshwater lakes. Fish become infected by the penetration of cercariae released from freshwater snails, and high infection pressures may be associated with mortalities in a Danish lake. Examination of two other freshwater lakes, combined with laboratory study, supported the notion. We investigated 77 freshwater fish from two lakes and the infection level suggested the occurrence of a high cercarial infection pressure in the Danish lakes. Dominant genera were Tylodelphys and Diplostomum covering a range of species identified by PCR and sequencing of the 18S (partial)-ITS1-5.8S-ITS2-28S (partial) of the rDNA. Cercariae of the prevalent species Diplostomum pseudospathaceum were used to infect zebrafish Danio rerio for the elucidation of short-term effects on the fish host. Zebrafish did not display abnormal behaviour when exposed to 200-400 cercariae, but a dosage of 600 and 1,000 cercariae/fish proved lethal. When fish were exposed to sublethal dosages, 19 out of 27 immune genes were significantly regulated and three genes encoding cytokine (IL 4/13B, IL-6 and IL-8) were upregulated at 3 hr post-infection (hpi), whereas others were downregulated especially at a later time point. We suggest that direct massive cercarial penetration of fish surfaces may be detrimental and may represent a threat to fish populations.
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http://dx.doi.org/10.1111/jfd.13496DOI Listing
July 2021

(Apicomplexa) in in Europe with a potential for spread.

Int J Parasitol Parasites Wildl 2021 Aug 2;15:270-275. Epub 2021 Jul 2.

Laboratory of Aquatic Pathobiology, Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark.

Four specimens of mallard () shot by local hunters (December 2020 to January 2021 along the eastern coastline of the island of Bornholm in the Baltic Sea) were diagnosed with a heavy load of sarcocysts in the musculature. Morphometric and molecular diagnosis based on rDNA (18 S, ITS1, 28 S) of parasites recovered from two of the birds revealed the causative pathogen to be . We further present novel sequences for the entire 5.8 S and ITS2 for this species. Elongate cysts (mean length 5.25 (SD 0.6) mm, width 1.37 (SD 0.2) mm) were recorded in all parts of the striated skeletal musculature of the birds. The main part (72%) of the 2585 cysts in one female mallard was located in the outer superficial pectoral musculature, with 11% in the inner pectoral musculature. Minor but significant parts were found in the dorsal, ventral abdominal, neck and head, legs, hand and arm (wing) musculature. No cysts were found in the smooth musculature. Each cyst contained a median of 3.2 mio bradyzoites indicating that more than 8 billion bradyzoites are available for infection of one or more predators/scavengers ingesting the bird. Bradyzoites (median length 13.5 μm (range 12.1-14.5) and median width 2.66 μm (range 2.1-3.3)) were highly resistant to proteinase treatment, which secures the passage through the stomach of the predator to its intestine where wall penetration takes place. One of the birds was ringed (tagged) in Sweden Island Øland in the Baltic Sea two years before being shot. This is documenting immigration of mallards from northern locations. The parasite species was originally described in North America in 1893 and was commonly reported in this region during the 20th century but not in Europe. Recent cases from Norway, Finland, Lithuania, Poland, UK and Hungary suggest that the species may be spreading geographically. Experienced duck hunters with a 40 years record of hunting on the island reported that this type of infection unprecedented. The final host is reported to be canines (fox, raccoon dog), skunk and mustelids, including ermines and American mink. Presence of these hosts in Europe may allow establishment of the life cycle and further colonization of the local duck populations which calls for implementation of a survey program in Europe.
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http://dx.doi.org/10.1016/j.ijppaw.2021.06.007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8264532PMC
August 2021

A Major QTL for Resistance to in Rainbow Trout.

Front Genet 2020 29;11:607558. Epub 2020 Dec 29.

Laboratory of Aquatic Pathobiology, Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.

Genetic selection of disease resistant fish is a major strategy to improve health, welfare and sustainability in aquaculture. Mapping of single nucleotide polymorphisms (SNP) in the fish genome may be a fruitful tool to define relevant quantitative trait loci (QTL) and we here show its use for characterization of resistant rainbow trout (). Fingerlings were exposed to the pathogen serotype O1 in a solution of 1.5 × 10 cfu/ml and observed for 14 days. Disease signs appeared 3 days post exposure (dpe) whereafter mortality progressed exponentially until 6 dpe reaching a total mortality of 55% within 11 days. DNA was sampled from all fish - including survivors - and analyzed on a 57 k Affymetrix SNP platform whereby it was shown that disease resistance was associated with a major QTL on chromosome 21 (Omy 21). Gene expression analyses showed that diseased fish activated genes associated with innate and adaptive immune responses. The possible genes associated with resistance are discussed.
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http://dx.doi.org/10.3389/fgene.2020.607558DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7802751PMC
December 2020

Negligible risk of zoonotic anisakid nematodes in farmed fish from European mariculture, 2016 to 2018.

Euro Surveill 2021 Jan;26(2)

AZTI, Food Research, Basque Research and Technology Alliance (BRTA), Bizkaia, Spain.

BackgroundThe increasing demand for raw or undercooked fish products, supplied by both aquaculture and fisheries, raises concerns about the transmission risk to humans of zoonotic fish parasites. This has led to the current European Union (EU) Regulation No 1276/2011 amending Annex III of Regulation (EC) No 853/2004 and mandating a freezing treatment of such products. Zoonotic parasites, particularly anisakid larvae, have been well documented in wild fish. Data on their presence in European aquaculture products, however, are still scarce, except for Atlantic salmon (), where the zoonotic risk was assessed as negligible, exempting it from freezing treatment.AimTo evaluate the zoonotic Anisakidae parasite risk in European farmed marine fish other than Atlantic salmon.MethodsFrom 2016 to 2018 an observational parasitological survey was undertaken on 6,549 farmed fish including 2,753 gilthead seabream (), 2,761 European seabass () and 1,035 turbot () from 14 farms in Italy, Spain and Greece. Furthermore, 200 rainbow trout () sea-caged in Denmark, as well as 352 seabream and 290 seabass imported in Italy and Spain from other countries were examined. Fish were subjected to visual inspection and candling. Fresh visceral organs/fillet samples were artificially digested or UV pressed and visually examined for zoonotic anisakid larvae.ResultsNo zoonotic parasites were found in any of the fish investigated.ConclusionsThe risk linked to zoonotic Anisakidae in the examined fish species from European mariculture appears negligible. This study laid the groundwork for considerations to amend the current EU regulation.
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http://dx.doi.org/10.2807/1560-7917.ES.2021.26.2.1900717DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7809721PMC
January 2021

Trematode diversity reflecting the community structure of Danish freshwater systems: molecular clues.

Parasit Vectors 2021 Jan 12;14(1):43. Epub 2021 Jan 12.

Laboratory of Aquatic Pathobiology, Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Via Stigbøjlen 7, 1870, Frederiksberg C, Copenhagen, Denmark.

Background: Digenean trematodes are parasitic platyhelminths that use several hosts in their life cycles and are thereby embedded in various ecosystems affected by local environmental conditions. Their presence in a habitat will reflect the presence of different host species and, as such, they can serve as ecological indicators. Only limited information on the occurrence of trematodes and their link to other trophic levels in the Danish freshwater ecosystems is currently available.Therefore, the main aim of the present study was to increase our knowledge in this field.

Methods: Snails were sampled from 21 freshwater lakes in Denmark, following which shedding procedures were performed, cercariae were recoved and the released parasites were identified using molecular tools (PCR and sequencing).

Results: A total of 5657 snail hosts belonging to ten species were identified, revealing a highly diverse parasite fauna comprising 22 trematode species. The overall trematode prevalence was 12.6%, but large variations occurred between host species. The snail host Lymnaea stagnalis showed the highest prevalence and also exhibited the highest diversity, accounting for 47.6% of the species richness.

Conclusions: This survey contributes updated information on parasite-host relations and compatibility and may assist in describing the ecological structure of the investigated Danish freshwater ecosystems.
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http://dx.doi.org/10.1186/s13071-020-04536-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7805065PMC
January 2021

Digenean trematodes in Hungarian freshwater aquacultures.

Food Waterborne Parasitol 2021 Mar 10;22:e00101. Epub 2020 Dec 10.

Institute for Veterinary Medical Research, Centre for Agricultural Research, Budapest, Hungary.

Occurrence of metacercariae of potentially zoonotic trematodes (Platyhelminthes: Digenea) in the musculature of common carp ( L. 1758) was monitored in four Hungarian aquacultures. Four geographically distinct fish farms (located in the Northwestern, Southwestern, Northeastern and Southeastern parts of Hungary) were selected for the investigation. From each farm, a total of 258 one-summer-old fingerlings were sampled and examined in the years 2016 and 2017. In addition, in 2017, we examined 60 market size specimens (30 two-summers and 30 three-summers) sampled from the most infected aquaculture in the Northeastern part of Hungary. The fish were euthanized and decapitated whereafter their musculature (fillets) was digested in a pepsin solution to isolate metacercariae from the tissue whereafter morphological and molecular analyses (PCR and sequencing of ITS region) were performed. Opisthorchiid metacercariae were not recovered but in one of the farms numerous metacercariae were detected in the musculature of carp. They were identified as cyathocotylid trematodes based on their morphological characteristics and by sequencing the ITS region. The infection levels proved to be remarkably different among the four fish farms. Carps from the Northeastern farm were infected by large numbers of cyathocotylid metacercariae, while 8 metacercariae were detected in the Northwestern aquaculture. In the other two farms (Southwestern and Southeastern) no infection was recorded. The infected farm is located close to a protected natural wetland habitat populated by a rich fauna of aquatic birds (potential final hosts) and snails (first intermediate host) which may create a higher risk of infection in the neighbouring fish farms.
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http://dx.doi.org/10.1016/j.fawpar.2020.e00101DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7750318PMC
March 2021

A non-lethal method for detection of Bonamia ostreae in flat oyster (Ostrea edulis) using environmental DNA.

Sci Rep 2020 09 30;10(1):16143. Epub 2020 Sep 30.

Laboratory of Aquatic Pathobiology, Department of Veterinary and Animal Science, University of Copenhagen, Stigbøjlen 7, 1870, Frederiksberg C, Denmark.

Surveillance and diagnosis of parasitic Bonamia ostreae infections in flat oysters (Ostrea edulis) are prerequisites for protection and management of wild populations. In addition, reliable and non-lethal detection methods are required for selection of healthy brood oysters in aquaculture productions. Here we present a non-lethal diagnostic technique based on environmental DNA (eDNA) from water samples and demonstrate applications in laboratory trials. Forty oysters originating from Limfjorden, Denmark were kept in 30 ppt sea water in individual tanks. Water was sampled 6 days later, after which all oysters were euthanized and examined for infection, applying PCR. Four oysters (10%) were found to be infected with B. ostreae in gill and mantle tissue. eDNA purified from the water surrounding these oysters contained parasite DNA. A subsequent sampling from the field encompassed 20 oysters and 15 water samples from 5 different locations. Only one oyster turned out positive and all water samples proved negative for B. ostreae eDNA. With this new method B. ostreae may be detected by only sampling water from the environment of isolated oysters or isolated oyster populations. This non-lethal diagnostic eDNA method could have potential for future surveys and oyster breeding programs aiming at producing disease-free oysters.
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http://dx.doi.org/10.1038/s41598-020-72715-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7527985PMC
September 2020

Physiological condition of Eastern Baltic cod, , infected with the parasitic nematode .

Conserv Physiol 2020 22;8(1):coaa093. Epub 2020 Sep 22.

National Institute of Aquatic Resources, Technical University of Denmark (DTU Aqua), Kemitorvet 201, Kgs. Lyngby 2800, Denmark.

Establishing relationships between parasite infection and physiological condition of the host can be difficult and therefore are often neglected when describing factors causing population declines. Using the parasite-host system between the parasitic nematode and the Eastern Baltic cod , we here shed new light on how parasite load may relate to the physiological condition of a transport host. The Eastern Baltic cod is in distress, with declining nutritional conditions, disappearance of the larger fish, high natural mortality and no signs of recovery of the population. During the latest decade, high infection levels with have been observed in fish in the central and southern parts of the Baltic Sea. We investigated the aerobic performance, nutritional condition, organ masses, and plasma and proximate body composition of wild naturally infected in relation to infection density with . Fish with high infection densities of had (i) decreased nutritional condition, (ii) depressed energy turnover as evidenced by reduced standard metabolic rate, (iii) reduction in the digestive organ masses, and alongside (iv) changes in the plasma, body and liver composition, and fish energy source. The significantly reduced albumin to globulin ratio in highly infected suggests that the fish suffer from a chronic liver disease. Furthermore, fish with high infection loads had the lowest Fulton's condition factor. Yet, it remains unknown whether our results steam from a direct effect of , or because in an already compromised nutritional state are more susceptible towards the parasite. Nevertheless, impairment of the physiological condition can lead to reduced swimming performance, compromising foraging success while augmenting the risk of predation, potentially leading to an increase in the natural mortality of the host. We hence argue that fish-parasite interactions must not be neglected when implementing and refining strategies to rebuild deteriorating populations.
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http://dx.doi.org/10.1093/conphys/coaa093DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7507771PMC
September 2020

Temperature and light effects on Trichobilharzia szidati cercariae with implications for a risk analysis.

Acta Vet Scand 2020 Sep 15;62(1):54. Epub 2020 Sep 15.

Laboratory of Aquatic Pathobiology, Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Stigbøjlen 7, 1870, Frederiksberg C, Denmark.

Background: Cercarial dermatitis (swimmer's itch) caused by bird schistosome cercariae, released from intermediate host snails, is a common disorder also at higher latitudes. Several cases were observed in the artificial Danish freshwater Ringen Lake frequently used by the public for recreational purposes. The lake may serve as a model system when establishing a risk analysis for this zoonotic disease. In order to explain high risk periods we determined infection levels of intermediate host snails from early spring to late summer (March, June and August) and elucidated the effect of temperature and light on parasite shedding, behavior and life span.

Results: Field studies revealed no shedding snails in March and June but in late summer the prevalence of Trichobilharzia szidati infection (in a sample of 226 pulmonate Lymnaea stagnalis snails) reached 10%. When investigated under laboratory conditions the cercarial shedding rate (number of cercariae shed per snail per day) was positively correlated to temperature raising from a mean of 3000 (SD 4000) at 7 °C to a mean of 44,000 (SD 30,000) at 27 °C). The cercarial life span was inversely correlated to temperature but the parasites remained active for up to 60 h at 20 °C indicating accumulation of cercariae in the lake during summer periods. Cercariae exhibited positive phototaxy suggesting a higher pathogen concentration in surface water of the lake during daytime when the public visits the lake.

Conclusion: The only causative agent of cercarial dermatitis in Ringen Lake detected was T. szidati. The infection risk associated with aquatic activities is low during spring and early summer (March-June). In late summer the risk of infection is high since the release, behavior and life span of the infective parasite larvae have optimal conditions.
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http://dx.doi.org/10.1186/s13028-020-00553-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7493345PMC
September 2020

Immune gene expression and genome-wide association analysis in rainbow trout with different resistance to Yersinia ruckeri infection.

Fish Shellfish Immunol 2020 Nov 11;106:441-450. Epub 2020 Aug 11.

Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C., Denmark.

Selective breeding programmes involving marker assisted selection of innately pathogen resistant strains of rainbow trout rely on reliable controlled infection studies, extensive DNA typing of individual fish and recording of expression of relevant genes. We exposed juvenile rainbow trout (6 h bath to 2.6 × 10 CFU mL) to the fish pathogen Yersinia ruckeri serotype O1, biotype 2, eliciting Enteric Red Mouth Disease ERM, and followed the disease progression over 21 days. Cumulative mortality reached 42% at 12 days post challenge (dpc) after which no disease signs were recorded. All fish were sampled for DNA-typing (50 k SNP chip, Affymetrix®) throughout the course of infection when they showed clinical signs of disease (susceptible fish) or at day 21 when fish showed no clinical signs of disease (survivors - resistant fish). Genome-wide association analyses of 1027 trout applying single nucleotide polymorphisms (SNPs) as markers revealed an association between traits (susceptible/resistant) and certain regions of the trout genome. It was indicated that multiple genes are involved in rainbow trout resistance towards ERM whereby it is considered a polygenic trait. A corresponding trout group was kept as non-exposed controls and a comparative expression analysis of central innate and adaptive immune genes in gills, spleen and liver was performed for three fish groups: 1) moribund trout exhibiting clinical signs 7 dpc (CS), 2) exposed fish without clinical signs at the same sampling point (NCS) and 3) surviving fish at 21 dpc (survivors). Immune genes encoding inflammatory cytokines (IL-1β, IL-2A, IL-6A, IL-8, IL-10A, IL-12, IL-17A/F2A, IL-17C1, IL-17C2, IL-22, IFNγ, TNFα), acute phase reactants (SAA, C3, cathelicidins, lysozyme) were expressed differently in CS and NCS fish. Correlation (negative or positive) between expression of genes and bacterial load suggested involvement of immune genes in protection. Down-regulation of adaptive immune genes including IgDm, IgDs, IgT and TCR-β was seen primarily in CS and NCS fish whereas survivors showed up-regulation of effector molecule genes such as cathelicidins, complement and lysozyme suggesting their role in clearing the infection. In conclusion, SNP analyses indicated that ERM resistance in rainbow trout is a multi-locus trait. The gene expression in surviving fish suggested that several immune genes are associated with the trait conferring resistance.
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http://dx.doi.org/10.1016/j.fsi.2020.07.023DOI Listing
November 2020

Contracaecum osculatum (sensu lato) infection of Gadus morhua in the Baltic Sea: inter- and intraspecific interactions.

Int J Parasitol 2020 09 15;50(10-11):891-898. Epub 2020 Jul 15.

Department of Veterinary and Animal Science, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C., Denmark. Electronic address:

The subpopulation of Atlantic cod, Gadus morhua, in the eastern part of the Baltic Sea has experienced a significant increase in infections with anisakid nematode larvae of the species Contracaecum osculatum sensu lato (s.l.) since the year 2000. The life cycle of the parasite includes seals and especially the grey seal, Halichoerus grypus, as final hosts, carrying the adult nematodes in the stomach, crustaceans (copepods, amphipods) as first intermediate hosts and various fish species (clupeids, sandeel) including cod as second intermediate/paratenic hosts. Cod with a body length below 28 cm are generally non-infected but experience increasing infection levels when they switch to a piscine diet (infected intermediate/paratenic hosts). We present an overall frequency distribution analysis of worms in 166 cod (body length 30-49 cm) collected in the spawning area over the last 5 years. It shows a fit to the negative binomial distribution, a prevalence of infection of 89.8%, a mean intensity of 29.3 parasites per fish (range 1-377) and a variance/mean ratio of 59.2 (≫1), indicating overdispersion. We present measurements of the adult Contracaecum osculatum (s.l.) specimens in the seal stomach and show that the parasites reach a maximum length of 6.6 cm (females) and 5.8 cm (males). L3s in sprat have a total length from 1to 11 mm whereas the larvae in cod liver are 3-27 mm. A decreasing mean worm length associated with high worm densities in cod (number of nematodes per liver) was recorded. Possible explanations might include timing of feeding on infected intermediate/paratenic hosts, intraspecific competition (crowding) between larvae in cod and host responses (indicated by a significant antibody production in cod against C. osculatum (s.l.) antigens). A significant negative correlation between infection intensity and muscle mass of cod was found, suggesting parasite-induced down-regulation of growth factors in cod.
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http://dx.doi.org/10.1016/j.ijpara.2020.06.003DOI Listing
September 2020

Parasites in the changing world - Ten timely examples from the Nordic-Baltic region.

Parasite Epidemiol Control 2020 Aug 5;10:e00150. Epub 2020 May 5.

Laboratory of Parasitology, Department of Bacteria, Parasites & Fungi, Infectious Disease Preparedness, Statens Serum Institut, Artillerivej 5, 2300 Copenhagen S, Denmark.

The world is changing, and parasites adapt. The Nordic-Baltic region in northern Europe - including the Nordic countries Denmark, Finland, Iceland, Norway and Sweden, and the Baltic States Estonia, Latvia and Lithuania - is facing new parasitological challenges due to changes in populations of parasites and their hosts and the spread of new parasites to the region due to climate change. Some changes can also be ascribed to increased awareness and detection. In this paper, we review and discuss a convenience selection of ten timely examples of recent observations that exemplify trends and challenges from different fields of parasitology, with particular focus on climate change and potential changes in epidemiology of pathogens in northern Europe. The examples illustrate how addressing parasitological challenges often requires both intersectoral and international collaboration, and how using both historical baseline data and modern methodologies are needed.
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http://dx.doi.org/10.1016/j.parepi.2020.e00150DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7232095PMC
August 2020

Rainbow trout Oncorhynchus mykiss skin responses to salmon louse Lepeophtheirus salmonis: From copepodid to adult stage.

Fish Shellfish Immunol 2020 Aug 15;103:200-210. Epub 2020 May 15.

SLRC - Sea Lice Research Centre, Department of Biological Sciences, University of Bergen, Thormøhlensgt. 55, Pb. 7803, 5020, Bergen, Norway. Electronic address:

The marine crustacean Lepeophtheirus salmonis (salmon louse) is a common ectoparasite of wild and farmed salmonids. The parasite has a complex ontogeny comprising eight instars. The planktonic copepodid stage settles on host skin and pass through five instars to reach the adult stage. The present study comprises an experimental infestation of Oncorhynchus mykiss (rainbow trout) with salmon lice and describes histopathology and host immune responses in skin beneath the louse at multiple time points encompassing all louse developmental stages. Each fish was exposed to 80 infective copepodids, a mean no. of 32 parasites reached the preadult I stage whereas a mean no. of 11 parasites reached the adult stage. A progression in the severity of cutaneous lesions was observed, and levels of immune gene transcripts at the attachment site revealed a dynamic response, initially related to innate immunity. Later, immune cells accumulated in the dermis concomitant with a moderate decrease in levels of transcripts characteristic of both innate and adaptive immune responses. The present study also demonstrates that the cutaneous immune response was mainly induced at lice affected sites, while non-affected skin resembled the skin of untreated control. This indicates that the skin cannot be regarded as a uniform organ and requires careful sampling at all salmon louse stages.
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http://dx.doi.org/10.1016/j.fsi.2020.05.014DOI Listing
August 2020

Gill amoebae from freshwater rainbow trout (Oncorhynchus mykiss): In vitro evaluation of antiparasitic compounds against Vannella sp.

J Fish Dis 2020 Jun 15;43(6):665-672. Epub 2020 Apr 15.

Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C, Denmark.

Gill parasitic infections challenge farming of rainbow trout (Oncorhynchus mykiss, Walbaum) in freshwater facilities. Apart from flagellates (Ichthyobodo, (Pinto) and ciliates (Ichthyophthirius (Fouquet), Ambiphrya (Raabe), Apiosoma (Blanchard), Trichodinella (Sramek-Husek) and Trichodina (Ehrenberg)), we have shown that amoebae are prevalent in Danish trout farms. Gills were isolated from farmed rainbow trout in six fish farms (conventional and organic earth pond and recirculated systems) and placed on non-nutrient agar (NNA) moistened with modified Neff's amoeba saline (AS) (15°C). Gill amoebae from all examined fish colonized the agar and were identified based on morphological criteria showing species within the genera Trinema (Dujardin) (family Trinematidae), Vannella (Bovee) (family Vannellidae). In addition, hartmannellid amoebae were recorded. We established a monoculture of Vannella sp., confirmed the genus identity by PCR and sequencing and performed an in vitro determination of antiparasitic effects (dose-response studies) of various compounds including sodium chloride (NaCl), hydrogen peroxide, peracetic acid, formalin, aqueous garlic and oregano extracts and a Pseudomonas H6 surfactant. All amoebae were killed in concentrations of 16.90 mg/ml (garlic), 17.90 mg/ml (oregano), NaCl (7.5 mg/ml), hydrogen peroxide (100 µg/ml), peracetic acid (0.03 µg/ml), formaldehyde (25 µg/ml) and the Pseudomonas H6 surfactant (250 µg/ml).
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http://dx.doi.org/10.1111/jfd.13162DOI Listing
June 2020

Immune response to Ichthyophthirius multifiliis and role of IgT.

Authors:
Kurt Buchmann

Parasite Immunol 2020 08 17;42(8):e12675. Epub 2019 Oct 17.

Department of Veterinary and Animal Science, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C, Denmark.

The parasitic ciliate Ichthyophthirius multifiliis causes white spot disease in freshwater fish worldwide. The theront penetrates external surfaces of the naïve fish where it develops into the feeding trophont stage and elicits a protective immune response both at the affected site as well as at the systemic level. The present work compiles data and presents an overall model of the protective reactions induced. A wide spectrum of inflammatory reactions are established upon invasion but the specific protection is provided by adaptive factors. Immunoglobulin IgT is involved in protection of surfaces in several fish species and is thereby one of the first adaptive immune molecules reacting with the penetrating theront. IgT producing lymphocytes occur in epithelia, dispersed or associated with lymphoid cell aggregations (skin epidermis, fins, gills, nostrils and buccal cavities) but they are also present in central immune organs such as the head kidney, spleen and liver. When theronts invade immunized fish skin, they are encountered by host factors which opsonize the parasite and may result in complement activation, phagocytosis or cell-mediated killing. However, antibody (IgT, IgM and IgD) binding to parasite cilia has been suggested to alter parasite behaviour and induce an escape reaction, whereby specific IgT (or other classes of immunoglobulin in fish surfaces) takes a central role in protection against the parasite.
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http://dx.doi.org/10.1111/pim.12675DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7507210PMC
August 2020

Endoparasitic helminths in Baltic salmon Salmo salar: ecological implications.

Dis Aquat Organ 2019 Sep;135(3):193-199

Department of Veterinary and Animal Science, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C 1870, Denmark.

Parasites in fish are ecological indicators, as they reflect the host's migration routes, feeding behavior and immune status. We performed a parasitological investigation of sea-running Baltic salmon to study the use of parasites as indicators for this fish stock. The host-a strain of Atlantic salmon Salmo salar-has been isolated for several millennia in the semi-enclosed brackish Baltic Sea, with limited migration to and from the North Sea. Twenty-four salmon (total body weight: 4.2-14.2 kg; total body length: 80-105 cm) were caught by spoon bait in the southern Baltic Sea during feeding migrations, necropsied shortly afterwards and internal organs subjected to parasitological investigation focusing on endoparasitic helminths. The pyloric region was heavily parasitized by the cestode Eubothrium crassum (100% prevalence; intensity: 97-273 parasites per infected fish), reflecting a diet of smaller pelagic fishes. The stomach contained the hemiurid digeneans Brachyphallus crenatus (95.8% prevalence; intensity: 8-151) and Hemiurus luehei (58.3% prevalence; intensity: 2-13), indicating a diet of clupeids. Schistocephalus solidus (25% prevalence; intensity: 1-2), liberated from ingested sticklebacks, the acanthocephalan Echinorhynchus truttae (54% prevalence; intensity: 1-13) and the adult nematode Hysterothylacium aduncum (29% prevalence; intensity: 1-13) were found in the intestine. The liver was parasitized by third-stage nematode larvae of Contracaecum osculatum (45.8% prevalence; intensity: 1-4), but these were growth-stunted and encapsulated. The parasite fauna differs markedly from salmon in North Atlantic waters, and the lack of purely marine parasite species indicates that the Baltic salmon has remained in the Baltic Sea during its life history.
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http://dx.doi.org/10.3354/dao03391DOI Listing
September 2019

Outbreak of Swimmer's Itch in Denmark.

Acta Derm Venereol 2019 Nov;99(12):1116-1120

Department of Dermatology, Aarhus University Hospital, DK-8200 Aarhus, Denmark.

Swimmer's itch, or cercarial dermatitis, is a waterborne non-communicable skin condition caused by schistosome cercariae released by aquatic snails. Cercarial dermatitis appears worldwide, but may be caused by different trematode species. The itchy maculopapular rash develops on exposed areas of the skin and typically resolves within 1-3 weeks. Shedding of infective larvae from snails is temperature dependent, and high temperatures and sunshine increase the risk of encountering the parasite and becoming infected. The unusually warm spring and summer of 2018 led to an increasing number of reports of the condition in Denmark and established a collaboration between the Department of Dermatology and the Faculty of Health and Medical Sciences, Department of Veterinary and Animal Sciences. This study explored the clinical picture of the disease, and demonstrated the occurrence of infected fresh water snail species in selected Danish water bodies. In conclusion, a risk of swimmer's itch in Denmark was confirmed.
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http://dx.doi.org/10.2340/00015555-3309DOI Listing
November 2019

Transcriptomic analysis of Baltic cod (Gadus morhua) liver infected with Contracaecum osculatum third stage larvae indicates parasitic effects on growth and immune response.

Fish Shellfish Immunol 2019 Oct 13;93:965-976. Epub 2019 Aug 13.

Department of Veterinary and Animal Science, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C, Denmark.

High infection levels due to third-stage larvae of the anisakid nematode Contracaecum osculatum have been documented in cod from the eastern part of the Baltic sea during the latest decades. The nematode larvae mainly infect the liver of Baltic cod and prevalence of infection has reached 100% with a mean intensity up to 80 parasites per host in certain areas and size classes. Low condition factors of the cod have been observed concomitant with the rise in parasite abundance suggesting a parasitic effect on growth parameters. To investigate any association between parasite infection and physiological status of the host we performed a comparative transcriptomic analysis of liver obtained from C. osculatum infected and non-infected cod. A total of 47,025 predicted gene models showed expression in cod liver and sequences corresponding to 2084 (4.43%) unigenes were differentially expressed in infected liver when compared to non-infected liver. Of the differentially expressed unigenes (DEGs) 1240 unigenes were up-regulated while 844 unigenes were down-regulated. The Gene Ontology (GO) enrichment analysis showed that 1304 DEGs were represented in cellular process and single-organism process, cell and cell part, binding and catalytic activity. As determined by the Kyoto Encyclopedia of Gene and Genomes (KEGG) Pathways analysis, 454 DEGs were involved in 138 pathways. Ninety-seven genes were related to metabolic pathways including carbohydrate, lipid, and amino acid metabolism. Thirteen regulated genes were playing a role in immune response such as Toll-like receptor signaling, NOD-like receptor signaling, RIG-I-like receptor signalling and thirty-six genes were associated with growth processes. This indicates that the nematode infection in Baltic cod may affect on molecular mechanisms involving metabolism, immune function and growth.
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http://dx.doi.org/10.1016/j.fsi.2019.08.034DOI Listing
October 2019

Protective effect of in-feed specific IgM towards Yersinia ruckeri in rainbow trout.

Fish Shellfish Immunol 2019 Oct 10;93:934-939. Epub 2019 Aug 10.

National Veterinary Institute, Technical University of Denmark, Frederiksberg C, Denmark. Electronic address:

Tightened regulations and an environmentally friendly approaches in fish production have greatly reduced the use of antibiotics but green solutions are continuously being explored. The use of functional feed may have a potential in the aquaculture sector in securing biomass and minimizing the loss from disease. In the present study, we tested the concept that blood from the fish slaughterhouse can be used for mass purification of specific antibodies which subsequently can be used for feeding fish and thereby confer protection against diseases. IgM was purified from serum from Yersinia ruckeri vaccinated rainbow trout and an IgM sandwich ELISA was developed for quantification of rainbow trout IgM. The purified IgM was encapsulated in alginate microparticles and top-coated in fish feed. IgM re-extracted from the alginate microparticles was shown to retain high reactivity towards Y. ruckeri antigens indicating that its bioactivity remained intact after encapsulation. IgM release from the alginate microparticles was only observed at high pH (pH 8.2) and minimal at low pH, indicating protection of IgM at low pH in the fish stomach during passage. In a feeding - challenge experiment (feeding 1 week before Y. ruckeri challenge and for two weeks following challenge), a statistically non-significant 10% lower mortality was observed in the high dose (400 μg IgM/fish/day fed over 3 weeks) group.
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http://dx.doi.org/10.1016/j.fsi.2019.08.024DOI Listing
October 2019

Differential immune gene response in gills, skin, and spleen of rainbow trout Oncorhynchus mykiss infected by Ichthyophthirius multifiliis.

PLoS One 2019 20;14(6):e0218630. Epub 2019 Jun 20.

Department of Veterinary and Animal Science, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C, Denmark.

Infection of rainbow trout with the parasitic ciliate Ichthyopthirius multifiliis induces differential responses in gills, skin and spleen. A controlled experimental infection was performed and expression of immune-relevant genes in skin, gills, and spleen were recorded by qPCR at day 1 and 8 after parasite exposure. Infection induced a marked reaction involving regulation of innate and adaptive immune genes in rainbow trout at day 8 post-infection. The expression level of a total of 22 out of 24 investigated genes was significantly higher in gills compared to skin reflecting the more sensitive and delicate structure of gills. Especially pro-inflammatory cytokines IL-6, IL-17 C1, regulatory cytokines IL-4/13A, IL-10, TGFβ, complement factor C5, chemokines CK10, CK12, acute phase proteins (precerebellin, hepcidin) and immunoglobulins (IgM, IgT) displayed differential expression levels. The spleen, a central immune organ with no trace of the parasite, showed elevated expression of IgM, IgT, complement factor C5 and chemokine CK10 (compared to skin and gills directly exposed to the parasite), indicating an interaction between the infected surface sites and central immune organs. This communication could be mediated by chemokines CK10 and CK12 and cytokine IL-4/13A and may at least partly explain the establishment of a systemic response in rainbow trout against the parasite.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0218630PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6586319PMC
February 2020

Haematology, blood biochemistry, parasites and pathology of common eider (Somateria mollisima) males during a mortality event in the Baltic.

Sci Total Environ 2019 Sep 21;683:559-567. Epub 2019 May 21.

Aarhus University, Department of Bioscience, Arctic Research Centre (ARC), Frederiksborgvej 399, PO Box 358, DK-4000 Roskilde, Denmark. Electronic address:

A mortality event at the Christiansø colony in the Baltic proper killed 115 common eiders (Somateria mollissima) in mid-May 2016. To complement previous studies of incubating females, 39 males were necropsied and from a subsample of these a biochemical and haematological profile was obtained. The birds were emaciated and cachexic having a 50% reduction in body mass. Twenty-nine eiders were diagnosed with hydropericardium, 15 had hunger edema, three birds had enteritis and a single air sac infection. All birds were infested with intestinal Polymorphus minutus and 32 of these with the intestinal Trematoda spp. Microscopic parasitic investigations identified endoparasitic trematodes of the families Bucephhalidae, Echinostomidae, Notocotyluridae and Levinsiniella. White blood cell count showed slight heterophilia and lymphopenia while the albumin:globulin ratio (0.28) indicated stress, immune supression and inflammatory reactions supported by a high heterophil:lymphocyte index (13). Declined plasma concentration of glucose, fructosamine, amylase, albumin and protein likewise indicated long-term starvation prior to mortality indicating phase III starvation (catabolism of protein). The dramatic increase in aspartate transaminase, glutamate-dehydrogenase, lactate-dehydrogenase and bile acids indicate liver disorders while dehydration, renal, heart and bone disorders was reflected in the increased uric acid, urea, phosphor and potassium values. These findings show that male eiders undergo long-term starvation and multi organ failure similar to that of incubating females previously reported from the same colony. It increases our knowledge of the physiology of starving eiders and add to our understanding of the recurrent mortality events in the colony that seems to be linked to changes in food availability being an important factor together with a warmer climate in a declining Baltic eider population. We recommend future studies to focus on food composition, migration patterns and environmental changes including parasitic infections and global warming.
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http://dx.doi.org/10.1016/j.scitotenv.2019.05.281DOI Listing
September 2019

Skin immune response of rainbow trout (Oncorhynchus mykiss) experimentally exposed to the disease Red Mark Syndrome.

Vet Immunol Immunopathol 2019 May 23;211:25-34. Epub 2019 Mar 23.

Unit for Fish and Shellfish Diseases, National Institute of Aquatic Resources, Technical University of Denmark, 2800, Kgs. Lyngby, Denmark.

Red Mark Syndrome (RMS) is a skin disease reported from farmed rainbow trout. Since the turn of the millennium it has been spreading through Europe. RMS is probably a bacterial disease caused by a Midichloria-like organism (MLO). It is non-lethal and causes little obvious changes in appetite or behavior but results in red hyperaemic skin lesions, which may lead to economic losses due to downgrading. Here we transfer RMS to naïve specific pathogen free (SPF) fish by cohabitation with RMS-affected seeder fish. During disease development we characterize local cellular immune responses and regulations of immunologically relevant genes in skin of the cohabitants by immunohistochemistry and qPCR. Skin samples from SPF controls and cohabitants (areas with and without lesions) were taken at 18, 61, 82 and 97 days post-cohabitation. Gene expression results showed that lesions had a Th1-type profile, but with concurrent high expression levels of all three classes of immunoglobulins (IgD, IgM and IgT). The marked local infiltration of IgD + cells in the skin lesions as well as a highly up-regulated expression of the genes encoding sIgD and mIgD indicate that this immunoglobulin class plays an important role in skin immunity in general and in RMS pathology in particular. The co-occurrence of an apparent B cell dominated immune reaction with a Th1-type profile suggests that the local production of antibodies is independent of the classical Th2 pathway.
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http://dx.doi.org/10.1016/j.vetimm.2019.03.008DOI Listing
May 2019

Effects of water depth on GBD associated with total dissolved gas supersaturation in Chinese sucker (Myxocyprinus asiaticus) in upper Yangtze River.

Sci Rep 2019 05 2;9(1):6828. Epub 2019 May 2.

Laboratory of Aquatic Pathobiology, Department of Veterinary and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, DK-1870, Frederiksberg C, Denmark.

Spillway water falling from hydroelectric power plant dams in the upper Yangtze River creates a high pressure in plunge pools below the dams allowing gasses to be dissolved at high rates. The resulting supersaturation persists many miles downstream the dam which may elicit mortality in river fishes associated with gas bubble disease (GBD). We have in a two-year study (2014-15) evaluated the effect of water depth on development of GBD in an endemic and endangered fish species, the Chinese sucker Myxocyprinus asiaticus, 24 km downstream of Xiangjaiba dam. Mortality and incidence of GBD were recorded and it was seen that water depth and survival time/GBD development was positively correlated. The physiological mechanisms explaining increased resistance to GBD with increased water depths (and thereby higher hydrostatic pressure) are discussed. The results may be applied in future management of fish resources in order to protect endangered endemic fishes in rivers affected by dam constructions.
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http://dx.doi.org/10.1038/s41598-019-42971-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6497699PMC
May 2019
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