Fish Parasites and Immunology

A special issue of Pathogens (ISSN 2076-0817). This special issue belongs to the section "Parasitic Pathogens".

Deadline for manuscript submissions: closed (31 December 2022) | Viewed by 18513

Special Issue Editor


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Guest Editor
Section of Parasitology and Aquatic Pathobiology, Faculty of Health and Medical Sciences, University of Copenhagen
Interests: fish immunology and parasitology; zebrafish as a model organism; host–pathogen interactions; in vivo real-time disease modeling; vaccinology

Special Issue Information

Dear Colleagues

This Special Issue of Pathogens will focus on Fish Parasites and Immunology. Even though the resolution of host–parasite interactions has improved during the last decade, there remain unresolved key issues, including the degree to which innate or adaptive immune mechanisms are involved. Fish have a highly evolved innate immune response and a more primitive adaptive response compared with mammals, and exactly why fish hosts are susceptible or resistant and how they develop memory remains a question of interest that involves many unresolved mechanisms. Evidence suggests that many cell types of the fish adaptive immune system are more innate-like when compared with mammals. More tools to determine fish immunology have become available and, in this Special Issue, we welcome original research or review papers that present novel findings on the immune response of fish to parasite infections.

Potential topics include, but are not limited to:

  1. a) fish parasites and immunological responses in fish;
    b) a deeper understanding of fundamental mechanisms in fish immunology; and
    c) new knowledge about fish host–parasite interactions for use in, e.g., prophylactic approaches such as the development of vaccines or treatments to control disease.
  2. In this Special Issue, we hope to present new knowledge within the scientific area of fish host–parasite interactions. A collection of high-impact articles on this subject may raise awareness about important parasite disease problems in wild or aquacultured fish and contribute new fundamental and applied knowledge to help us further understand and combat diseases in fish caused by parasites.

Prof. Louise Von Gersdorff Jørgensen
Guest Editor

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Keywords

  • fish parasites
  • immunology
  • innate responses
  • adaptive responses
  • host–parasite interactions

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Published Papers (5 papers)

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Research

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26 pages, 4999 KiB  
Article
Intestinal Transcriptomic and Histologic Profiling Reveals Tissue Repair Mechanisms Underlying Resistance to the Parasite Ceratonova shasta
by Damien E. Barrett, Itziar Estensoro, Ariadna Sitjà-Bobadilla and Jerri L. Bartholomew
Pathogens 2021, 10(9), 1179; https://doi.org/10.3390/pathogens10091179 - 13 Sep 2021
Cited by 10 | Viewed by 2603
Abstract
Background: Myxozoan parasites infect fish worldwide causing significant disease or death in many economically important fish species, including rainbow trout and steelhead trout (Oncorhynchus mykiss). The myxozoan Ceratonova shasta is a parasite of salmon and trout that causes ceratomyxosis, a disease [...] Read more.
Background: Myxozoan parasites infect fish worldwide causing significant disease or death in many economically important fish species, including rainbow trout and steelhead trout (Oncorhynchus mykiss). The myxozoan Ceratonova shasta is a parasite of salmon and trout that causes ceratomyxosis, a disease characterized by severe inflammation in the intestine resulting in hemorrhaging and necrosis. Populations of O. mykiss that are genetically fixed for resistance or susceptibility to ceratomyxosis exist naturally, offering a tractable system for studying the immune response to myxozoans. The aim of this study was to understand how steelhead trout that are resistant to the disease respond to C. shasta once it has become established in the intestine and identify potential mechanisms of resistance. Results: Sequencing of intestinal mRNA from resistant steelhead trout with severe C. shasta infections identified 417 genes differentially expressed during the initial stage of the infection compared to uninfected control fish. A strong induction of interferon-gamma and interferon-stimulated genes was evident, along with genes involved in cell adhesion and migration. A total of 11,984 genes were differentially expressed during the late stage of the infection, most notably interferon-gamma, interleukin-6, and immunoglobulin transcripts. A distinct hardening of the intestinal tissue and a strong inflammatory reaction in the intestinal submucosa including severe hyperplasia and inflammatory cell infiltrates were observed in response to the infection. The massive upregulation of caspase-14 early in the infection, a protein involved in keratinocyte differentiation might reflect the rapid onset of epithelial repair mechanisms, and the collagenous stratum compactum seemed to limit the spread of C. shasta within the intestinal layers. These observations could explain the ability of resistant fish to eventually recover from the infection. Conclusions: Our results suggest that resistance to ceratomyxosis involves both a rapid induction of key immune factors and a tissue response that limits the spread of the parasite and the subsequent tissue damage. These results improve our understanding of the myxozoan–host dialogue and provide a framework for future studies investigating the infection dynamics of C. shasta and other myxozoans. Full article
(This article belongs to the Special Issue Fish Parasites and Immunology)
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17 pages, 2514 KiB  
Article
First Report of Blood Fluke Pathogens with Potential Risk for Emerging Yellowtail Kingfish (Seriola lalandi) Aquaculture on the Chilean Coast, with Descriptions of Two New Species of Paradeontacylix (Aporocotylidae)
by Fabiola A. Sepúlveda, Luis A. Ñacari and Maria Teresa González
Pathogens 2021, 10(7), 849; https://doi.org/10.3390/pathogens10070849 - 6 Jul 2021
Cited by 5 | Viewed by 3424
Abstract
Blood flukes are digeneans that infect wild and farmed fish that can cause a severe and potentially lethal disease in farmed fish. These parasites are undetectable in the larval stage based on macroscopic observations in the definitive host with the infection becoming evident [...] Read more.
Blood flukes are digeneans that infect wild and farmed fish that can cause a severe and potentially lethal disease in farmed fish. These parasites are undetectable in the larval stage based on macroscopic observations in the definitive host with the infection becoming evident when eggs accumulate in the branchial vessels. There are nine known species of the genus Paradeontacylix and seven exclusively parasitize Seriola spp. from several geographical areas. Seriola lalandi aquaculture farms are emerging at various localities in northern Chile. Here, we report, for the first time, two blood fluke species parasitizing S. lalandi in the Southeastern Pacific (Chile). In the laboratory, the gills and heart of fish were removed. The retained blood flukes were separated according to the infection site, fixed in 70% or 95% ethanol for taxonomic and molecular analysis, respectively. Morphometrical differences among the fluke species were evaluated with a principal component analysis (PCA) using proportional body measurements. Phylogenetic trees were constructed based on 28S rDNA, cox1 mDNA using Bayesian inference (BI), and maximum likelihood (ML). Based on morphology, morphometry, and molecular analyses, two new species are proposed: P. humboldti n. sp. from the gills and P. olivai n. sp. from the heart of S. lalandi. Both were clearly distinguished from other species of Paradeontacylix by a combination of morphologic features (posterior tegumental spines, testes arrangement, body size). The genetic distance (based on cox1) among species was >10%. P. humboldti n. sp. and P. olivai n. sp. are sister species (with a common ancestor) independent of P. godfreyi from S. lalandi in Australia. The newly identified parasites may pose a risk to farmed S. lalandi as aporocotylids have been the cause of diseases in farmed fish from other geographical areas. In addition, some cages of S. lalandi are currently maintained in an open circulating system, which could favor the transmission of these parasites (if involved hosts are present in the environment). Full article
(This article belongs to the Special Issue Fish Parasites and Immunology)
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8 pages, 1956 KiB  
Article
Changes in the Splenic Melanomacrophage Centre Surface Area in Southern Bluefin Tuna (Thunnus maccoyii) Are Associated with Blood Fluke Infections
by Barbara F. Nowak, Mai Dang, Claire Webber, Lukas Neumann, Andrew Bridle, Roberto Bermudez and Daryl Evans
Pathogens 2021, 10(1), 79; https://doi.org/10.3390/pathogens10010079 - 18 Jan 2021
Cited by 8 | Viewed by 2574
Abstract
Melanomacrophage centres (MMCs) are aggregates of macrophages accumulating various pigments. They have been proposed as an indicator of fish immune response. Blood flukes are common parasites in farmed fish. Two cohorts of wild Southern Bluefin Tuna (Thunnus maccoyi) were examined at [...] Read more.
Melanomacrophage centres (MMCs) are aggregates of macrophages accumulating various pigments. They have been proposed as an indicator of fish immune response. Blood flukes are common parasites in farmed fish. Two cohorts of wild Southern Bluefin Tuna (Thunnus maccoyi) were examined at transfer, before treatment against blood flukes (pre-treatment) and at harvest. MMCs were assessed in histological sections using image analysis, while Cardicola forsteri and Cardicola orientalis infection severity was determined using qPCR, count of adult flukes in heart flushes and count of eggs in gill filaments. Fish from both cohorts showed the same pattern in the changes in the surface area of MMCs. The surface area of splenic MMCs increased over the ranching duration and was positively correlated to the PCR determined copy numbers of Cardicola forsteri ITS2 rDNA in the gills of those fish. However, the infection with blood fluke was more variable, both between cohorts and individuals within the same cohort. Eggs of blood fluke were detected in renal MMCs using histology. Cardicola forsteri had a higher prevalence than Cardicola orientalis. This study contributes to our understanding of blood fluke infections in Southern Bluefin Tuna and their interactions with MMCs. Full article
(This article belongs to the Special Issue Fish Parasites and Immunology)
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11 pages, 1811 KiB  
Article
Natural Feed Additives Modulate Immunity and Mitigate Infection with Sphaerospora molnari (Myxozoa: Cnidaria) in Common Carp: A Pilot Study
by Vyara O. Ganeva, Tomáš Korytář, Hana Pecková, Charles McGurk, Julia Mullins, Carlos Yanes-Roca, David Gela, Pavel Lepič, Tomáš Policar and Astrid S. Holzer
Pathogens 2020, 9(12), 1013; https://doi.org/10.3390/pathogens9121013 - 2 Dec 2020
Cited by 6 | Viewed by 2952
Abstract
Myxozoans are a diverse group of cnidarian parasites, including important pathogens in different aquaculture species, without effective legalized treatments for fish destined for human consumption. We tested the effect of natural feed additives on immune parameters of common carp and in the course [...] Read more.
Myxozoans are a diverse group of cnidarian parasites, including important pathogens in different aquaculture species, without effective legalized treatments for fish destined for human consumption. We tested the effect of natural feed additives on immune parameters of common carp and in the course of a controlled laboratory infection with the myxozoan Sphaerospora molnari. Carp were fed a base diet enriched with 0.5% curcumin or 0.12% of a multi-strain yeast fraction, before intraperitoneal injection with blood stages of S. molnari. We demonstrate the impact of these treatments on respiratory burst, phagocytosis, nitric oxide production, adaptive IgM+ B cell responses, S. molnari-specific antibody titers, and on parasite numbers. Both experimental diets enriched B cell populations prior to infection and postponed initial parasite proliferation in the blood. Curcumin-fed fish showed a decrease in reactive oxygen species, nitric oxide production and B cell density at late-stage infection, likely due to its anti-inflammatory properties, favoring parasite propagation. In contrast, multi-strain yeast fraction (MsYF)-fed fish harbored the highest S. molnari-specific antibody titer, in combination with the overall lowest parasite numbers. The results demonstrate that yeast products can be highly beneficial for the outcome of myxozoan infections and could be used as effective feed additives in aquaculture. Full article
(This article belongs to the Special Issue Fish Parasites and Immunology)
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Review

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20 pages, 580 KiB  
Review
Zebrafish as a Model for Fish Diseases in Aquaculture
by Louise von Gersdorff Jørgensen
Pathogens 2020, 9(8), 609; https://doi.org/10.3390/pathogens9080609 - 27 Jul 2020
Cited by 41 | Viewed by 5683
Abstract
The use of zebrafish as a model for human conditions is widely recognized. Within the last couple of decades, the zebrafish has furthermore increasingly been utilized as a model for diseases in aquacultured fish species. The unique tools available in zebrafish present advantages [...] Read more.
The use of zebrafish as a model for human conditions is widely recognized. Within the last couple of decades, the zebrafish has furthermore increasingly been utilized as a model for diseases in aquacultured fish species. The unique tools available in zebrafish present advantages compared to other animal models and unprecedented in vivo imaging and the use of transgenic zebrafish lines have contributed with novel knowledge to this field. In this review, investigations conducted in zebrafish on economically important diseases in aquacultured fish species are included. Studies are summarized on bacterial, viral and parasitic diseases and described in relation to prophylactic approaches, immunology and infection biology. Considerable attention has been assigned to innate and adaptive immunological responses. Finally, advantages and drawbacks of using the zebrafish as a model for aquacultured fish species are discussed. Full article
(This article belongs to the Special Issue Fish Parasites and Immunology)
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