DOCSLIB.ORG

Home Sweet Home — Trout Parasites

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Home Sweet Home — Trout Parasites length of your hand. Some live on a single fi sh, whilst others have complex life cycles with multiple hosts, spanning many years and travelling hundreds of miles before they mature and reproduce. Many parasites lead a benign existence, tolerated by healthy fi sh without causing any obvious distress. However, by their very nature, parasites divert energy from their host for their own survival and reproduction. Consequently, some parasite infections can lead to debilitation of individual fi sh and serious disease problems within populations. Here, Chris Williams and Shaun Leonard give us a brief introduction to some of those parasites and problems. The Fish Louse, Argulus Figure 1: The white, fl uffy fungal The fi sh louse, Argulus, is a resident of rivers infection of Saprolegnia, tends to and lakes and one of the most familiar be a secondary infection on open parasites encountered by anglers. Three abrasions and sores species have been recorded from British freshwater fi sh and all may be found on the skin and fi ns of trout. The largest is Argulus coregoni (Figure 2), a parasite with a preference for running water so most likely to be encountered by the wild trout angler. Home Adults, up to 10mm in size, are light brown and well camoufl aged on the fl anks of trout; the black, beady eyespots can give them away (Figure 3). Suckers allow the parasite to move with surprising agility, yet clamp like a limpet when faced with risk of detachment. Sweet Home Infections of Argulus in the wild are often limited to odd ones and twos, tolerated by A guide to some of the creatures most healthy fi sh. Large aggregations of fi sh, that call a trout’s body home, prolonged low fl ows and warm temperatures can cause parasite numbers to increase. Heavy by Dr. Chris Williams and Shaun Leonard. infections can be extremely damaging, the continual feeding and attachment behaviour arasites are natural ranging environments. Consequently, damaging the skin and draining the fi sh’s components of healthy parasites are everywhere. energy reserves. aquatic ecosystems. They There are reports from the 60s and 70s Over 50 parasite species have been of salmon and sea trout ‘black with lice’ have evolved to infect most recorded from UK trout populations, ranging during extended low fl ows. More recently, Pliving organisms and exist in wide from microscopic protists to tapeworms the dry summers have led to rising abundance of Catch our releases. The magazine for the progressive game angler www.flyfishing-and-flytying.co.uk www.wildtrout.org 45 Salmo Trutta TROUT PARASITES A. coregoni on brown trout in some northern infected with opportunistic organisms like attracted to fi sh odour rather than repelled. rivers, although subsequent rainfall has the fl uffy, white fungus Saprolegnia (Figure Such behavioural changes increase the dispersed these infections. The ubiquitous 1). This adds to the confusion, because chances of the shrimp becoming the next A. foliaceus is the scourge of stillwater trout fi sh without UDN can naturally contract mouthful of a passing fi sh. This is one of fi sheries, threatening the economic viability Saprolegnia, especially spawning male many examples where parasites intricately of some. In such cases, lice may be found in trout and salmon whose thinned skin and re-wire their host to promote their own their thousands on individual fi sh, causing propensity to fi ght each other makes them development and reproduction. severe irritation and rapid condition loss. more vulnerable to infection. Recent research in Poland suggests that UDN-exposed brown Proliferative Kidney Disease The Gill Maggot, trout are less able to maintain the internal Proliferative Kidney Disease (PKD) is a Ergasilus sieboldi chemistry of the body, contributing to the serious problem in rainbow trout culture, Figure 6: the fi sh leech, Piscicola. Note the sucker Figure 7: the freshwater shrimp, Gammarus pulex, This parasite, fi rst recorded in Britain in the fi sh’s death. Some authorities suggest that caused by a tiny myxozoan parasite called at each end of the worm-like body and red infected with the larva of a spiny-headed worm, colouration from blood within. evident as a bright orange spot. 1960s, is most likely to be a problem for trout UDN proliferates where there are large Tetracapsuloides bryosalmonae. Clinical in lakes or gently-fl owing river reaches, since numbers of fi sh congregating in low-fl ow disease signs include swelling of the kidney it is a tiny copepod crustacean (a little over rivers and sunny conditions but again this is that can lead to mortality during the 1mm in length), unable to cope with much not totally consistent. summer months. In Europe, there is some fl ow. Only the females parasitise fi sh, but Large-scale mortalities of salmon and sea evidence to suggest that PKD is increasing quite spectacularly, with modifi ed antennae trout, attributed to UDN, were reported in its distribution and severity. The disease has gripping on whilst mouthparts rasp away at many UK rivers in the 1960s and 70s and recently been linked to the decline of wild the delicate gill tissues (Figure 4). problems reappear periodically. Fish health Figure 2: Argulus coregoni – note the large suckers brown trout in Switzerland, disease of Arctic Heavy infections undoubtedly cause fi sh scientists do not consider UDN to be a for attaching to the fi sh’s skin and numerous char in Iceland and also mortality in salmon mortalities, but thus far, the parasite has only widespread problem in the UK. However, swimming legs. parr in Norway. been a problem in coarse fi sh communities further efforts are needed to monitor this For many years, the life cycle of T. and stocked stillwater trout fi sheries. The condition and new molecular diagnostic bryosalmonae eluded scientists, hindering common name, the gill maggot, derives from techniques could help with fi nding a causative understanding of parasite transmission and Figure 8: a microscopic close-up of the head of Figure 9: cysts of Eustrongylides fi lling the Pomphorhynchus laevis – note the proboscis of abdomen of a brown trout. the appearance of attached females carrying agent in the future. disease dynamics. It was purely by chance the worm lined with attachment hooks and the a pair of white, elongate egg sacs, usually in that a scientist discovered the parasite within bulb, designed to plug the parasite fi rmly within the spring and summer (Figure 5). The Spiny-Headed Worm, free-living freshwater bryozoans – tiny fi lter- the gut of an infected fi sh. Pomphorhynchus feeders that grow freely on tree roots and The Fish Leeches, Piscicola Pomphorhynchus laevis, also known as the rocks in our rivers. The Nematode Worm, As with most parasites, light infections and Hemiclepsis ‘orange peril’, belongs to a group of parasites The parasite responsible for PKD is Eustrongylides are tolerated by trout with few adverse Fish leeches are common, obvious parasites known as the spiny-headed worms or widespread in the UK, but no serious disease Nematodes are common parasites of fi sh, effects. It is only when infections proliferate of trout, especially in stillwaters and slower Acanthocephala. problems have as yet been recorded in our but are often overlooked due to their tiny that problems arise. Recent investigations Figure 3: Argulus coregoni sheltering behind the river reaches, visible as a red-brown, worm- The array of spines that cover the head of pectoral fi n of a brown trout wild trout populations. However, little is size or apparently harmless existence. have revealed unusually heavy infections of like creature up to 30mm in length, attached this parasite make it a master of attachment known about the impact of this parasite in But at over 40mm in length and coloured Eustrongylides in some UK wild brown trout to the fi sh’s skin (Figure 6). (Figure 8). During attachment, the entire the wild and how changing environmental bright red, Eustrongylides is a conspicuous populations. Affected fi sh appear swollen They feed on the fi sh’s blood, biting head of the parasite is forced through the conditions could alter disease emergence in parasite that infects the body cavity of and lethargic. Such infections also cause through the skin, holding position with gut wall into the body cavity. Infl ation of a the future. There is some concern that rising trout (Figure 9). Each parasite lies coiled ovary degeneration, greatly reducing their a sucker at each end of the body. Heavy bulb just beyond the neck plugs the parasite water temperatures and eutrophication could within its own white, fi brous cyst, which reproductive potential. Studies are underway infestations might cause individual fi sh fi rmly in place, the body hanging free within all promote the proliferation of bryozoans provides protection until its host is eaten by the Environment Agency to assess the problems through loss of body fl uids and the fi sh’s gut. Here, the parasite absorbs and the parasites within. Collaborative by a fi sh-eating bird. It is only then that the extent and severity of these cases. leech bite wounds can become infected. Once nutrients from passing food and deposits its studies between the Environment Agency, parasite becomes re-animated, attaching Should you encounter any disease problems the leeches have had their fi ll, they drop off eggs that are fl ushed out with the faeces. Cefas, Aberdeen University and the Natural and maturing within the bird’s gut. Death in trout or require more information on and hide amongst weed and stones, digesting Many trout and grayling anglers will be History Museum are underway to improve of the fi sh can also trigger these nematodes the parasites mentioned, please contact the their meal.
Load more

Recommended publications
  • A Guide to Culturing Parasites, Establishing Infections and Assessing Immune Responses in the Three-Spined Stickleback
    ARTICLE IN PRESS Hook, Line and Infection: A Guide to Culturing Parasites, Establishing Infections and Assessing Immune Responses in the Three-Spined Stickleback Alexander Stewart*, Joseph Jacksonx, Iain Barber{, Christophe Eizaguirrejj, Rachel Paterson*, Pieter van West#, Chris Williams** and Joanne Cable*,1 *Cardiff University, Cardiff, United Kingdom x University of Salford, Salford, United Kingdom { University of Leicester, Leicester, United Kingdom jj Queen Mary University of London, London, United Kingdom #Institute of Medical Sciences, Aberdeen, United Kingdom **National Fisheries Service, Cambridgeshire, United Kingdom 1Corresponding author: E-mail: [email protected] Contents 1. Introduction 3 2. Stickleback Husbandry 7 2.1 Ethics 7 2.2 Collection 7 2.3 Maintenance 9 2.4 Breeding sticklebacks in vivo and in vitro 10 2.5 Hatchery 15 3. Common Stickleback Parasite Cultures 16 3.1 Argulus foliaceus 17 3.1.1 Introduction 17 3.1.2 Source, culture and infection 18 3.1.3 Immunology 22 3.2 Camallanus lacustris 22 3.2.1 Introduction 22 3.2.2 Source, culture and infection 23 3.2.3 Immunology 25 3.3 Diplostomum Species 26 3.3.1 Introduction 26 3.3.2 Source, culture and infection 27 3.3.3 Immunology 28 Advances in Parasitology, Volume 98 ISSN 0065-308X © 2017 Elsevier Ltd. http://dx.doi.org/10.1016/bs.apar.2017.07.001 All rights reserved. 1 j ARTICLE IN PRESS 2 Alexander Stewart et al. 3.4 Glugea anomala 30 3.4.1 Introduction 30 3.4.2 Source, culture and infection 30 3.4.3 Immunology 31 3.5 Gyrodactylus Species 31 3.5.1 Introduction 31 3.5.2 Source, culture and infection 32 3.5.3 Immunology 34 3.6 Saprolegnia parasitica 35 3.6.1 Introduction 35 3.6.2 Source, culture and infection 36 3.6.3 Immunology 37 3.7 Schistocephalus solidus 38 3.7.1 Introduction 38 3.7.2 Source, culture and infection 39 3.7.3 Immunology 43 4.
    [Show full text]
  • Viral Haemorrhagic Septicaemia Virus (VHSV): on the Search for Determinants Important for Virulence in Rainbow Trout Oncorhynchus Mykiss
    Downloaded from orbit.dtu.dk on: Nov 08, 2017 Viral haemorrhagic septicaemia virus (VHSV): on the search for determinants important for virulence in rainbow trout oncorhynchus mykiss Olesen, Niels Jørgen; Skall, H. F.; Kurita, J.; Mori, K.; Ito, T. Published in: 17th International Conference on Diseases of Fish And Shellfish Publication date: 2015 Document Version Publisher's PDF, also known as Version of record Link back to DTU Orbit Citation (APA): Olesen, N. J., Skall, H. F., Kurita, J., Mori, K., & Ito, T. (2015). Viral haemorrhagic septicaemia virus (VHSV): on the search for determinants important for virulence in rainbow trout oncorhynchus mykiss. In 17th International Conference on Diseases of Fish And Shellfish: Abstract book (pp. 147-147). [O-139] Las Palmas: European Association of Fish Pathologists. General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. DISCLAIMER: The organizer takes no responsibility for any of the content stated in the abstracts.
    [Show full text]
  • Proteome Analysis Reveals a Role of Rainbow Trout Lymphoid Organs During Yersinia Ruckeri Infection Process
    www.nature.com/scientificreports Correction: Author Correction OPEN Proteome analysis reveals a role of rainbow trout lymphoid organs during Yersinia ruckeri infection Received: 14 February 2018 Accepted: 30 August 2018 process Published online: 18 September 2018 Gokhlesh Kumar 1, Karin Hummel2, Katharina Noebauer2, Timothy J. Welch3, Ebrahim Razzazi-Fazeli2 & Mansour El-Matbouli1 Yersinia ruckeri is the causative agent of enteric redmouth disease in salmonids. Head kidney and spleen are major lymphoid organs of the teleost fsh where antigen presentation and immune defense against microbes take place. We investigated proteome alteration in head kidney and spleen of the rainbow trout following Y. ruckeri strains infection. Organs were analyzed after 3, 9 and 28 days post exposure with a shotgun proteomic approach. GO annotation and protein-protein interaction were predicted using bioinformatic tools. Thirty four proteins from head kidney and 85 proteins from spleen were found to be diferentially expressed in rainbow trout during the Y. ruckeri infection process. These included lysosomal, antioxidant, metalloproteinase, cytoskeleton, tetraspanin, cathepsin B and c-type lectin receptor proteins. The fndings of this study regarding the immune response at the protein level ofer new insight into the systemic response to Y. ruckeri infection in rainbow trout. This proteomic data facilitate a better understanding of host-pathogen interactions and response of fsh against Y. ruckeri biotype 1 and 2 strains. Protein-protein interaction analysis predicts carbon metabolism, ribosome and phagosome pathways in spleen of infected fsh, which might be useful in understanding biological processes and further studies in the direction of pathways. Enteric redmouth disease (ERM) causes signifcant economic losses in salmonids worldwide.
    [Show full text]
  • Notophthalmus Viridescens) by a New Species of Amphibiocystidium, a Genus of Fungus-Like Mesomycetozoan Parasites Not Previously Reported in North America
    203 Widespread infection of the Eastern red-spotted newt (Notophthalmus viridescens) by a new species of Amphibiocystidium, a genus of fungus-like mesomycetozoan parasites not previously reported in North America T. R. RAFFEL1,2*, T. BOMMARITO 3, D. S. BARRY4, S. M. WITIAK5 and L. A. SHACKELTON1 1 Center for Infectious Disease Dynamics, Biology Department, Penn State University, University Park, PA 16802, USA 2 Department of Biology, University of South Florida, Tampa, FL 33620, USA 3 Cooperative Wildlife Research Lab, Department of Zoology, Southern Illinois University, Carbondale, IL 62901, USA 4 Department of Biological Sciences, Marshall University, Huntington, WV 25755, USA 5 Department of Plant Pathology, Penn State University, University Park, PA 16802, USA (Received 21 March 2007; revised 17 August 2007; accepted 20 August 2007; first published online 12 October 2007) SUMMARY Given the worldwide decline of amphibian populations due to emerging infectious diseases, it is imperative that we identify and address the causative agents. Many of the pathogens recently implicated in amphibian mortality and morbidity have been fungal or members of a poorly understood group of fungus-like protists, the mesomycetozoans. One mesomycetozoan, Amphibiocystidium ranae, is known to infect several European amphibian species and was associated with a recent decline of frogs in Italy. Here we present the first report of an Amphibiocystidium sp. in a North American amphibian, the Eastern red-spotted newt (Notophthalmus viridescens), and characterize it as the new species A. viridescens in the order Dermocystida based on morphological, geographical and phylogenetic evidence. We also describe the widespread and seasonal distribution of this parasite in red-spotted newt populations and provide evidence of mortality due to infection.
    [Show full text]
  • Common Diseases of Wild and Cultured Fishes in Alaska
    COMMON DISEASES OF WILD AND CULTURED FISHES IN ALASKA Theodore Meyers, Tamara Burton, Collette Bentz and Norman Starkey July 2008 Alaska Department of Fish and Game Fish Pathology Laboratories The Alaska Department of Fish and Game printed this publication at a cost of $12.03 in Anchorage, Alaska, USA. 3 About This Booklet This booklet is a product of the Ichthyophonus Diagnostics, Educational and Outreach Program which was initiated and funded by the Yukon River Panel’s Restoration and Enhancement fund and facilitated by the Yukon River Drainage Fisheries Association in conjunction with the Alaska Department of Fish and Game. The original impetus driving the production of this booklet was from a concern that Yukon River fishers were discarding Canadian-origin Chinook salmon believed to be infected by Ichthyophonus. It was decided to develop an educational program that included the creation of a booklet containing photographs and descriptions of frequently encountered parasites within Yukon River fish. This booklet is to serve as a brief illustrated guide that lists many of the common parasitic, infectious, and noninfectious diseases of wild and cultured fish encountered in Alaska. The content is directed towards lay users, as well as fish culturists at aquaculture facilities and field biologists and is not a comprehensive treatise nor should it be considered a scientific document. Interested users of this guide are directed to the listed fish disease references for additional information. Information contained within this booklet is published from the laboratory records of the Alaska Department of Fish and Game, Fish Pathology Section that has regulatory oversight of finfish health in the State of Alaska.
    [Show full text]
  • Temperature-Driven Proliferation of Tetracapsuloides Bryosalmonae in Bryozoan Hosts Portends Salmonid Declines
    DISEASES OF AQUATIC ORGANISMS Vol. 70: 227–236, 2006 Published June 23 Dis Aquat Org Temperature-driven proliferation of Tetracapsuloides bryosalmonae in bryozoan hosts portends salmonid declines S. Tops, W. Lockwood, B. Okamura* School of Biological Sciences, Philip Lyle Research Building, University of Reading, Whiteknights, PO Box 228, Reading RG6 6BX, UK ABSTRACT: Proliferative kidney disease (PKD) is an emerging disease of salmonid fishes. It is pro- voked by temperature and caused by infective spores of the myxozoan parasite Tetracapsuloides bryosalmonae, which develops in freshwater bryozoans. We investigated the link between PKD and temperature by determining whether temperature influences the proliferation of T. bryosalmonae in the bryozoan host Fredericella sultana. Herein we show that increased temperatures drive the pro- liferation of T. bryosalmonae in bryozoans by provoking, accelerating and prolonging the production of infective spores from cryptic stages. Based on these results we predict that PKD outbreaks will increase further in magnitude and severity in wild and farmed salmonids as a result of climate-driven enhanced proliferation in invertebrate hosts, and urge for early implementation of management strategies to reduce future salmonid declines. KEY WORDS: Temperature · Climate change · Salmonids · Proliferative kidney disease · Myxozoa · Freshwater bryozoans · Covert infections Resale or republication not permitted without written consent of the publisher INTRODUCTION The source of PKD was obscure until freshwater bryozoans (benthic, colonial invertebrates) were iden- Disease outbreaks in natural and agricultural sys- tified recently as hosts of the causative agent (Ander- tems are increasing in both severity and frequency son et al. 1999), which was described as Tetracapsu- (Daszak et al. 2000, Subasinghe et al.
    [Show full text]
  • Shellfish Diseases and Their Management in Commercial Recirculating Systems
    Shellfish Diseases and Their Management in Commercial Recirculating Systems Ralph Elston AquaTechnics & Pacific Shellfish Institute PO Box 687 Carlsborg, WA 98324 Introduction Intensive culture of early life stages of bivalve shellfish culture has been practiced since at least the late 1950’s on an experimental basis. Production scale culture emerged in the 1970’s and today, hathcheries and nurseries produce large numbers of a variety of species of oysters, clams and scallops. The early life stage systems may be entirely or partially recirculating or static. Management of infectious diseases in these systems has been a challenge since their inception and effective health management is a requisite to successful culture. The diseases which affect early life stage shellfish in intensive production systems and the principles and practice of health management are the subject of this presentation. Shellfish Diseases and Management Diseases of bivalve shellfish affecting those reared or harvested from extensive culture primarily consist of parasitic infections and generally comprise the reportable or certifiable diseases. Due to the extensive nature of such culture, intervention options or disease control are limited. In contrast, infectious diseases known from early life stages in intensive culture systems tend to be opportunistic in nature and offer substantial opportunity for management due to the control that can be exerted at key points in the systems. In marine shellfish hatcheries, infectious organisms can enter the system from three sources: brood stock, seawater source and algal food source. Once an organism is established in the system, it may persist without further introduction. Bacterial infections are the most common opportunistic infection in shellfish hatcheries.
    [Show full text]
  • Chemical Signaling in Diatom-Parasite Interactions
    Friedrich-Schiller-Universität Jena Chemisch-Geowissenschaftliche Fakultät Max-Planck-Institut für chemische Ökologie Chemical signaling in diatom-parasite interactions Masterarbeit zur Erlangung des akademischen Grades Master of Science (M. Sc.) im Studiengang Chemische Biologie vorgelegt von Alina Hera geb. am 30.03.1993 in Kempten Erstgutachter: Prof. Dr. Georg Pohnert Zweitgutachter: Dr. rer. nat. Thomas Wichard Jena, 21. November 2019 Table of contents List of Abbreviations ................................................................................................................ III List of Figures .......................................................................................................................... IV List of Tables ............................................................................................................................. V 1. Introduction ............................................................................................................................ 1 2. Objectives of the Thesis ....................................................................................................... 11 3. Material and Methods ........................................................................................................... 12 3.1 Materials ......................................................................................................................... 12 3.2 Microbial strains and growth conditions ........................................................................ 12 3.3
    [Show full text]
  • First Evidence of Carp Edema Virus Infection of Koi Cyprinus Carpio in Chiang Mai Province, Thailand
    viruses Case Report First Evidence of Carp Edema Virus Infection of Koi Cyprinus carpio in Chiang Mai Province, Thailand Surachai Pikulkaew 1,2,*, Khathawat Phatwan 3, Wijit Banlunara 4 , Montira Intanon 2,5 and John K. Bernard 6 1 Department of Food Animal Clinic, Faculty of Veterinary Medicine, Chiang Mai University, Chiang Mai 50100, Thailand 2 Research Center of Producing and Development of Products and Innovations for Animal Health and Production, Faculty of Veterinary Medicine, Chiang Mai University, Chiang Mai 50100, Thailand; [email protected] 3 Veterinary Diagnostic Laboratory, Faculty of Veterinary Medicine, Chiang Mai University, Chiang Mai 50100, Thailand; [email protected] 4 Department of Pathology, Faculty of Veterinary Science, Chulalongkorn University, Bangkok 10330, Thailand; [email protected] 5 Department of Veterinary Biosciences and Public Health, Faculty of Veterinary Medicine, Chiang Mai University, Chiang Mai 50100, Thailand 6 Department of Animal and Dairy Science, The University of Georgia, Tifton, GA 31793-5766, USA; [email protected] * Correspondence: [email protected]; Tel.: +66-(53)-948-023; Fax: +66-(53)-274-710 Academic Editor: Kyle A. Garver Received: 14 November 2020; Accepted: 4 December 2020; Published: 6 December 2020 Abstract: The presence of carp edema virus (CEV) was confirmed in imported ornamental koi in Chiang Mai province, Thailand. The koi showed lethargy, loss of swimming activity, were lying at the bottom of the pond, and gasping at the water’s surface. Some clinical signs such as skin hemorrhages and ulcers, swelling of the primary gill lamella, and necrosis of gill tissue, presented. Clinical examination showed co-infection by opportunistic pathogens including Dactylogyrus sp., Gyrodactylus sp.
    [Show full text]
  • Acquired Resistance to Kudoa Thyrsites in Atlantic Salmon Salmo Salar Following Recovery from a Primary Infection with the Parasite
    Aquaculture 451 (2016) 457–462 Contents lists available at ScienceDirect Aquaculture journal homepage: www.elsevier.com/locate/aqua-online Acquired resistance to Kudoa thyrsites in Atlantic salmon Salmo salar following recovery from a primary infection with the parasite Simon R.M. Jones ⁎, Steven Cho, Jimmy Nguyen, Amelia Mahony Pacific Biological Station, 3190 Hammond Bay Road, Nanaimo, British Columbia V9T 6N7, Canada article info abstract Article history: The influence of prior infection with Kudoa thyrsites or host size on the susceptibility of Atlantic salmon post- Received 19 August 2015 smolts to infection with the parasite was investigated. Exposure to infective K. thyrsites in raw seawater (RSW) Received in revised form 30 September 2015 was regulated by the use of ultraviolet irradiation (UVSW). Naïve smolts were exposed to RSW for either Accepted 2 October 2015 38 days (440 degree-days, DD) or 82 days (950 DD) after which they were maintained in UVSW. Control fish Available online 9 October 2015 were maintained on UVSW only. Microscopic examination at day 176 (1985 DD) revealed K. thyrsites infection in nearly 90% of exposed fish but not in controls. Prevalence and severity of the infection decreased in later sam- ples. Following a second exposure of all fish at day 415 (4275 DD), prevalence and severity were elevated in the UVSW controls compared to previously exposed fish groups, suggesting the acquisition of protective immunity. In a second experiment, naïve smolts were exposed to RSW at weights of 101 g, 180 g, 210 g or 332 g and the prevalence and severity of K. thyrsites in the smallest fish group were higher than in any other group.
    [Show full text]
  • Pathogenicity and Infectivity of Saprolegnia Species in Atlantic Salmon (Salmo Salar L.) and Their Eggs
    Pathogenicity and infectivity of Saprolegnia species in Atlantic salmon (Salmo salar L.) and their eggs Mwansa Mathilda Songe Thesis for the degree of Philosophiae Doctor Norwegian University of Life Sciences Oslo 2015 CONTENTS 1 ACKNOWLEDGEMENTS .................................................................................................................... 1 2 SUMMARY.............................................................................................................................................. 3 3 SAMMENDRAG (Summary in Norwegian) ......................................................................................... 6 4 LIST OF PAPERS ................................................................................................................................... 9 5 ABSTRACTS ......................................................................................................................................... 11 6 INTRODUCTION ................................................................................................................................. 14 6.1 GENERAL INTRODUCTION ........................................................................................................ 14 6.2 SAPROLEGNIA – THE ORGANISM ........................................................................................... 16 CHARACTERISTICS OF THE OOMYCETES ................................................................................... 16 SECRETORY BEHAVIOUR OF OOMYCETES .................................................................................
    [Show full text]
  • Geographic Distribution of Tetracapsuloides Bryosalmonae Infected fi Sh in Swiss Rivers: an Update
    Aquat. Sci. 69 (2007) 3–10 1015-1621/07/010003-8 DOI 10.1007/s00027-006-0843-4 Aquatic Sciences © Eawag, Dübendorf, 2007 Research Article Geographic distribution of Tetracapsuloides bryosalmonae infected fi sh in Swiss rivers: an update Thomas Wahli1,*, Daniel Bernet1, Pascale April Steiner1,2 and Heike Schmidt-Posthaus1 1 Centre for Fish and Wildlife Health, Laenggassstrasse 122, P.O. Box 8466, CH-3001 Bern, Switzerland 2 Federal Offi ce for the Environment, CH-3003 Bern, Switzerland Received: 1 November 2005; revised manuscript accepted: 3 July 2006 Abstract. Proliferative kidney disease (PKD) has been sampling sites, T. bryosalmonae-infected fi sh were recognized as a potential threat to brown trout (Salmo found. The prevalence of infected fi sh at individual sites trutta) populations in Switzerland. A study performed in ranged from 0% to 100%. Infection intensity, judged on 2000/2001 on 139 sampling sites from 127 rivers in Swit- the basis of histological and immunohistochemical eval- zerland revealed a wide distribution of fi sh infected by uation for the degree of parasite infection, varied greatly Tetracapsuloides bryosalmonae, the causative agent of between and within sites. PKD-positive sites were found PKD. The present study aimed to complement this data- in all areas of Switzerland. The wide distribution of the set by studying a further 115 sample sites from 91 rivers disease in Swiss rivers indicates that PKD may be a caus- and 4 fi sh farms. Mainly brown trout were investigated ative factor for the catch decline of brown trout, which for the presence of T. bryosalmonae by a combination of was suggested over recent decades in Switzerland.
    [Show full text]