Molecular and SEM studies on Thaparocleidus vistulensis (Siwak, 1932) (Monopisthocotyla, Ancylodiscoididae).

Presenting new molecular and scanning electron microscope (SEM) features, this study gives additional data to the better knowledge of Thaparocleidus vistulensis (Siwak, 1932) (Monopisthocotyla, Ancylodiscoididae), a parasite of the European catfish Silurus glanis Linnaeus, 1758 (Siluriformes, Siluridae) cultured in a commercial fish farm in Hungary. In addition, notes on the early development of sclerotized anchors are also provided. The main morphological difference of T.

Location and elimination of third stage larvae in Atlantic herring L.

We here describe the location of anisakid third stage larvae in Atlantic herring L. caught in the North Sea in August 2023. We further demonstrate how industrial processing (mechanical gutting, removal of entrails, head, tail, hypaxial anterior musculature and vertebral column) reduces the overall infection and worm load in the musculature.

Transversotrema hafniensis n. sp. infection in Poecilia reticulata by cercariae released from Melanoides tuberculata in Denmark.

Background: Exotic and ornamental fish are highly popular companion animals resulting in a significant transcontinental trade of fish, invertebrates and aquatic plants. A major issue is the diseases associated with these organisms, as they have a major impact on health of the fish in both public and private household aquaria. A secondary issue is the trade with these products, which potentially may expand the distribution area and spread a range of diseases to new habitats.

Validation of a QTL associated with resistance to Vibrio anguillarum in rainbow trout (Oncorhynchus mykiss).

Vibriosis is a bacterial disease in fish caused by the Gram negative bacterium Vibrio anguillarum with severe impact on rainbow trout (Oncorhynchus mykiss) farming. Sustainable control methods should be developed and we here show that marker assisted selective breeding of fish naturally resistant to the disease is feasible. We have validated the use of a single nucleotide polymorphism (SNP) marker SNP AX-89,945,921 (QTL on chromosome 21).

: Response of Vaccinated Large Rainbow Trout to Different Strains.

Background: Although is recognized as the causative pathogen of rainbow trout fry syndrome (RTFS), often resulting in high fry mortality, it is also responsible for bacterial cold water disease (BCWD) in large and older rainbow trout (). These older fish do not experience high mortality, but sustain, through the shedding of bacteria, a constant infection pressure at farm level, which exposes fry to an unnecessary infection risk. We have produced and assessed the immunogenicity of an experimental injection BCWD vaccine, which may be used to decrease the shedding of bacteria from older fish.

Responses towards eyefluke (Diplostomum pseudospathaceum) in different genetic lineages of rainbow trout.

Marker-assisted selective breeding of fish with higher levels of resistance towards specific pathogens may improve fish health, but the impact of host genotype on susceptibility to multiple pathogen infections is still poorly investigated. This study examined the resistance in rainbow trout Oncorhynchus mykiss towards infection with the eye fluke Diplostomum pseudospathaceum. We used genetically selected rainbow trout, carrying SNPs associated with resistance towards the parasitic ciliate Ichthyophthirius multifiliis, and exposed the fish to eye fluke cercariae.

Integrative analyses of probiotics, pathogenic infections and host immune response highlight the importance of gut microbiota in understanding disease recovery in rainbow trout (Oncorhynchus mykiss).

Aims: Given the pivotal role played by the gut microbiota in regulating the host immune system, great interest has arisen in the possibility of controlling fish health by modulating the gut microbiota. Hence, there is a need to better understand of the host-microbiota interactions after disease responses to optimize the use of probiotics to strengthen disease resilience and recovery.

Methods And Results: We tested the effects of a probiotic feed additive in rainbow trout and challenged the fish with the causative agent for enteric red mouth disease, Yersinia ruckeri.

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

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.

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

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 .

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.

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.

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

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.

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

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.

A Major QTL for Resistance to in Rainbow Trout.

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.

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

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.

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

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.

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

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.

Anisakid nematode larvae in the liver of Atlantic cod Gadus morhua L. from West Greenland.

Anisakid nematode larvae occur frequently in the liver of Atlantic cod, but merely few infection data from cod in waters around Greenland exist. The present study reports the occurrence of third-stage anisakid larvae in the livers of 200 Atlantic cod caught on fishing grounds along the West coast of Greenland (fjord systems of Maniitsoq) in May, June, August and September 2017. Classical and molecular helminthological techniques were used to identify the nematodes.

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

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.

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

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).

Injection Vaccines Formulated with Nucleotide, Liposomal or Mineral Oil Adjuvants Induce Distinct Differences in Immunogenicity in Rainbow Trout.

Protection facilitated by the widespread use of mineral oil adjuvanted injection vaccines in salmonid fish comes with adverse effects of varying severity. In this study, we characterized the immunological profiles of two alternative vaccine formulations, both with proven efficacy and an improved safety profile in rainbow trout. Experimental injection vaccines were prepared on an identical whole-cell bacterin platform and were formulated with CpG oligodeoxynucleotides, a liposomal (CAF01) or a benchmark mineral oil adjuvant, respectively.

Endoparasitic helminths in Baltic salmon Salmo salar: ecological implications.

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.

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

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.

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

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.