Diseases of Fish

Diseases of Fish
Instructor:
Terry W. Campbell, DVM, PhD
Zoological Medicine, Service Chief
Colorado State University
(970) 297-1219
Email: [email protected]
The purpose of this 1 1/2-hour block of instruction is to gain knowledge and experience
in the common diseases of ornamental fish. Pet fish are one of the most numerous
companion animals in households in the United States. Increasingly, fish owners are
consulting with veterinarians about fish diseases. Likewise, veterinarians in clinical
practice are increasingly seeking help from veterinary pathologists.
Instruction will focus on the common diseases of fish with emphasis on pet fish or those
kept in public aquaria. Clinical assessment involved in the assessment of a piscine
patient involves a medical history, evaluation of the captive environment that includes
water quality assessment, and a physical examination. Routine sample collection
procedures during the examination include blood collection for a blood profile and wet
mount examination of mucus smears, gill clip biopsy, and fin clip biopsy. The disease
discussion will include common noninfectious and infectious disorders of fish. Infectious
disorders will be divided into parasitic, bacterial, viral, and fungal etiologies.
6/11/2012
Terry Campbell, DVM, PhD
Zoological medicine
Colorado State University
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Husbandry-related
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Bacterial
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Fungal
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Viral
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Parasitic
Environmental hypoxia
Hypercarbia
Temperature stress
Water is too acidic
Water is too alkaline
Improper salinity
Nutritional deficiency
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Nutritional disorders
 Hepatic lipidosis
 Emaciation
 Loss of dorsal musculature
 Big head and small body
 GI disorders
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Trauma
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Toxicities
 Ammonia, nitrites, nitrates
 Metal
 Chlorine/ Chloramine
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Many possible etiologies
 Inadequate nutrition
 Inadequate water quality
 Intestinal diplomonad flagellates
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Air embolism or gas bubble disease
 Supersaturation of gases in water
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Opportunistic pathogens
 Gram-negative aerobes and facultative anaerobes
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Diagnosis based on kidney culture
 Bacteremia
 Septicemia
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Use lab familiar with aquatic pathogens
 Culture fish isolates at room temperature
 Marine pathogens require culture media high
in salt
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Lethargy
Anorexia
Cutaneous hemorrhages and
ulcers
Fin rot
Ascites (“Dropsy”)
Exophthalmia
Color changes
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Marine fish, primarily
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Acute and chronic disorders
 Cutaneous ulcers with muscle necrosis
 Septicemia
 Enteritis
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Important species of marine tropicals
 V. damsela
 V. olginolyticus
 V. anquillarium
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A. hydrophila complex
 Affects all freshwater fish
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A. salmonicida
 Cold water fish
 Carp, goldfish, koi
▪ Ulcerative dermatitis
▪ Furunculosis - blisters
 Trout
▪ Septicemia
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Emphysematous putrefactive disease EPD
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Hemorrhagic septicemia in marine fish
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Lesions similar to vibriosis
 E. tarda
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Enteric septicemia of catfish (ESC)
 E. ictaluri
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 Vesicular dermatitis and muscle cavitation
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 Necrotizing nephritis and splenitis
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Enteric Redmouth Disease
Important pathogen of salmonids
 Blind fish with dark discoloration that
cannot find food
 Varies from other bacterial septicemias
Gross lesions
Histopathology
 Granulomatous and necrotizing nephritis,
splenitis, hepatitis, endocarditis and
pancreatitis
 Intracytoplasmic gram-positive bacteria
 Reddened skin erosions mainly on the head
or mouth
▪ Especially the lower jaw
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S. iniae, S. difficilis, S. parauberis, S.
milleri, S. shiloi
Non-specific signs of septicemia
 “Dropsy”
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Mycobacterium
 M. fortuitum: freshwater
 M. marinum: marine
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Nocardia kampachi
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General clinical signs
 Intracoelomic serosanginous fluid
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Nephritis, endocarditis, splenomegaly
Neurologic disorder with infection in
nervous system
 Chronic wasting
 Granulomatous lesions
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Myxobacterial disease
Flavobacterium columnare, formerly, Flexibacter
columnaris
 Mounds or columns of long rods
 Haystacks with gliding movements
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Necrotic ulcers or growths on skin, fins, or
gills
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Causes
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Poor water quality
Stress
Mis-use of antibiotics
Immunosuppression
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Saprolegniasis: white, fuzzy mold on skin
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Ichthyophonus hoferi: granulomas in organs
 Marine fish
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Hundreds of known viruses that affect fish
 Freshwater or marine
 DNA viruses
 DNA iridovirus
 RNA viruses
 Large wart-like tumorous growths
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Carp pox: cyprinid herpesvirus i
 Benign epidermal hyperplasia
 White to gray plaques on skin
A serious emerging disease
Major losses in koi
 Mass mortalities in common carp
 Virus is highly contagious
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 Via water, feces, or direct contact
Pale, swollen, mottled gills- dyspnea
 Abnormal skin coloration, sunken
eyes
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Species-specific herpesvirus,IcHV-1
Virus attacks all major organ systems
yellowish coelomic fluid
Punctate hemorrhage in the viscera
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Rhabdovirus of the genus Novirhabdovirus
Major cause of mortality of freshwater
salmonids (Rainbow and brown trout)
Hemorrhage and necrosis of hematopoetic
tissue
 Relative lack of pancreatic damage
 Relatively normal intestine and gills
 Lack of damage to eosinophilic granular cells of
stratum compactum
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Aquabirnavirus
Clinical signs
 Neurological signs
 Trailing white feces
 Dorsal darkening
 Abdominal distension
 Exophthalmos
 Hemorrhage, pale gills
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Acute death in fingerling trout
 Salmonids
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Rhabdovirus carpio
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Direct life cycle
Most are commensals and harmless
Captivity increases susceptibility to infection
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Nonspecific clinical signs
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 Darkened skin, dropsy, and exophthalmia
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Necropsy
 Immunosuppression
 Small hemorrhages throughout body
 High host population densities
 Ascites
 Coelomitis
 Enteritis
 Edema of internal organs
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Ichthyophthirius (“Ich”): freshwater fish
Cryptocaryon: marine fish
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Trophozoites
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 Round, ciliated, U-shaped nucleus
 Slow rolling motion
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Clinical signs
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Pathogenesis
 Ectoparasite feeds on host cells
 Burrow into epidermis
 Excessive mucus production
 Resistant cyst
 Flashing, restlessness, respiratory distress, white
spots (theront), death
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Freshwater and marine fish
Ciliated, circular, flattened with denticular
rings
 Clinical signs
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Irregular swimming
Flashing
Respiratory distress
Skin disorders
Chilodonella: freshwater fish
Brooklynella: marine fish
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Tetrahymena: freshwater fish
Uronema: marine fish
 Respiratory distress, clamped fins, depression,
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Free-living infusorian become secondary
pathogen
Oval, flattened, heart-shaped with cilia in rows
Slow circular movements
Clinical signs
Pear-shaped, actively motile ciliates
Clinical signs
 Discolored areas on skin surrounded by hemorrhage
sudden death
 Excessive mucus and gill hemorrhage
 Highly invasive
 Found in internal organs
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Difficult to treat
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May have direct life cycles
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Resistant cyst stages
 Hemoflagellates have indirect life cycles
Freshwater fish only
 Bell-shaped ciliated protozoa
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 Apical cilia
 Body contracts on coiled stalk
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Clinical signs
 White tuft on surface of skin or fins
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Ichthyobodo (Costia) : freshwater and marine
fish
Small, actively motile, comma-shaped
flagellates
 Move in a circular motion when attached
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Nonmotile dinoflagellate containing chlorophyll
 Encyst in skin and gills
 Form motile, flagellate dinospores
Clinical signs: “velvet disease” or “rust disease”
Destroys gill lamellae
Hexamita and Spironucleus
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 Freshwater and marine fish
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Asymptomatic
Unknown pathogenesis
Incidental finding in
 GI flagellate protozoans
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Piscinoodinium: freshwater fish
Amyloodinium: marine fish
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Clinical signs
 Irregular swimming, flashing, inappetence, death
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 Massive infestation likely Spironucleus
 Blood films
Clinical signs
 Tissue imprints (kidneys)
 Anorexia
 Lethargy
 Death
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Intracellular parasites that produce spores
Hemogregarines and piroplasms
 Indirect life cycles
 Found in blood
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Coccidia
 Direct life cycles
 Low pathogenicity in intestines
▪ Weight loss
▪ Yellow fluid feces
 Fatal extraintestinal infections
▪ Tissue coccidia
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Plistophora hyphessobryconis: freshwater fish
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Small (<20um), unicellular, intracellular
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Obligate parasites with one spindleshaped polar capsule within their spores
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Skinny disease of Zebra fish
 “Neon tetra disease”- fatal to neon tetras
 White areas in muscle
 Aberrant swimming
 Chronic debilitation
 Enclosed in enlarged host cells (xenomes) of skin,
muscle, GI tract, nerves
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Glugea, Pleistophora, Nosema
 Marine fish
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Glugea hiraldi
 White spot disease of sea horses
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Highly pathogenic
Intracellular involving many organs
Many genera
Nodules in skin and gills
Resemble microsporidia
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Hoferellus carassii
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Formerly known as Mitraspora cyprini
Goldfish and Koi
Severely bloated fish that live for months
Enlarged kidneys
 Except they have two spindle-shaped polar capsules
within their spores
 Require an intermediate host
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Henneguya ictaluri
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Primarily channel catfish fingerlings
Inflamed gill lamellae with trophozoite stage
Proliferative gill disease (PGD)
 Hamburger gill disease
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Myxobus cerebralis: whirling disease of
salmonids
 Indirect life cycle
 Whirling behavior, mis-shaped head, jaws, and
spines, black tail
 Death
▪ Destruction of skeleton and organs of equilibrium
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Cartilage degeneration and necrosis
Intralesional ovoid to ellipsoidal spores
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Freshwater or marine
Monogeneans
 Haptor or attachment organ
 Direct life cycle
 Lives on skin, gills, and fins
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Digeneans
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Endoparasites
Indirect life cycle
Adults with two suckers,y-shaped gut live in gi tract
Larvae encyst throughout body
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Haptor or attachment organ
Direct life cycle
Feed on skin, gills, and fins
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A monogenean skin and gill parasite
 Freshwater and marine fish
 2 points at anterior end, anterior sucker, no
 Cloudy skin, excessive mucus, hemorrhage
eyespots
 Haptor with 2 large hooks surrounded by small
hooklets
 Viviparous - embryos with hooks
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A monogenean gill parasites of freshwater
fish
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 4 points at anterior end
Typically asymptomatic infections in wild
fish
 Found in nearly any tissue
 Anterior sucker
 4 eyespots
 Haptor with 2 hooks surrounded by small
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Gill digeneans
 Can cause significant morbidity and mortality
hooklets
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Cryptocotyle: black spot in marine fish
 Cercariae shed from snail and penetrate skin of fish
 Black spots are encysted metacercaria
▪ Host produces melanin pigment around cyst
 Indirect life cycle
▪ Definitive host is fish eating bird
▪ Intermediate hosts: snail, then fish
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Free - living worms related to trematodes
The best known is the tang turbellarian
 Causes black ich
 Hypermelanization reaction -dark foci on the skin
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Lesions are similar to those of digenean
metacercariae
Adult worms in intestine
Larval forms in peritoneal cavity , liver, or
muscle
 Indirect life cycle
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 Intermediate hosts: crustacean, then fish
 Final host is piscivorus bird or mammal
Most infected fish are asymptomatic
 Heavy infestation- marked necrosis of
tissues occupied by larvae
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Fish are either intermediate or definitive hosts
Adult worms in digestive tract
Larval forms encysted in tissues
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Thorny headed worms
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Rare in cultured and aquarium fish
 Indirect life cycle requiring one or more
intermediate hosts
▪ Crustacean
▪ Fish
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Obligate intestinal parasite of fish
▪ Can damage intestinal wall
▪ Cause occlusion of lumen
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Branchiurans
 Ectoparasites
 Dorsoventrally flattened body
 Prehensile suckers to attach to fish
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Copepods
 Diversity of body form
 Body segments fused
 Variable appendages
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Sea louse, Anchor worm, Fish maggot
 Sea louse resembles the fish louse
▪ A serious problem in salmon production
 Lernaea or Anchor worm is important parasite
of freshwater aquarium and pond fish
 Fish maggot, Ergasilus, occurs in the gills of
freshwater fish
Argulus (fish louse)
Direct life cycle
Cutaneous lesion and respiratory distress
 Damages gills
 Cutaneous ulcers
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Lernaea [anchor worm]
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Elongated copepod embeds its head into skin
Y-shaped egg sacs
Direct life cycle in freshwater
Clinical signs
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 Tricaine
 Benzocaine
 2 – phenoxyethanol
▪ Cutaneous lesions
▪ Localized irritation and hemorrhage
 Barbiturates – sodium pentobarbital
 Inhalant anesthetics
 Rx
▪ Manual removal
▪ Organophosphate
Tumors are occasionally seen in aquarium
species, especially goldfish
 Any tissue can be affected
 Histopathologic criteria for malignancy in
mammals does not always apply to fish
 Metastasis is rare
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Accepted methods for humane euthanasia
 Carbon dioxide
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Eiras JC, et. al. Fish Diseases, Vols 1 and 2, 2008
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Noga EJ. Fish Diseases, Diagnosis and Treatment, 2nd ed, 2010
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Roberts RR. Fish Pathology, 3rd ed, 2001
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Woo PTK, et. al. Diseases and Disorders of Finfish in Cage Culture
2002
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Lymphoma
Neurilemmoma/ neurofibroma
Schwannoma
Fibrosarcoma
Pigment cell tumors, especially melanoma Thyroid adenoma/ adenocarcinoma
Hepatoma/ hepatocarcinoma
Testicular adenoma
39. http://www.fws.gov/midwest/LaCrosseFishHealthCenter/EntericSeptic.html
49. http://www.bettainfo.com/columnaris-cotton-wool-disease-flex-flexibacter
50. http://en.wikipedia.org/wiki/File:Columnaris_disease.jpg
61 http://www.americanaquariumproducts.com/Columnaris.html and
http://guramikampus.blogspot.com/2010/10/saprolegniasis-penyakit-pada-telur.html
65. http://auscichlids.com/forum/index.php?topic=2573.0
66. http://splendorkoipond.blogspot.com/2011/06/carp-pox.html and http://www.backyardpuddle.ca/health.html
68. http://indomahseer.wordpress.com/disease/koi-herpes-virus-khv-gill-rot/
69. http://ag.ansc.purdue.edu/courses/aq448/diseases/virus.htm
71. http://dnr.wi.gov/fish/health/vhs.html and http://www.biotechweblog.com/50226711/fish_viral_hemorrhagic_septicemia_virus_approach_epidemic_proportions.php
. http://www.discusfishs.com/discus-fish-diseases-t4.html and http://sfrc.ufl.edu/fasextension/AquaticAnimalHealth/ExamplesFishDiseases.html
76. http://www.discusfishs.com/discus-fish-diseases-t4.html and http://sfrc.ufl.edu/fasextension/AquaticAnimalHealth/ExamplesFishDiseases.html
77. http://uknishikigoi.com/s/treatments/
79. http://protist.i.hosei.ac.jp/pdb/images/Ciliophora/Chilodonella/sp_1.html
84. http://sfrc.ufl.edu/fas-extension/AquaticAnimalHealth/ExamplesFishDiseases.html
87. http://www.scielo.br/scielo.php?pid=S1984-29612011000100019&script=sci_arttext
91. http://www.practicalfishkeeping.co.uk/content.php?sid=3729
92. http://zebrafish.org/zirc/health/diseaseManual.php
96. http://www.aquariumsknowledge.com/goldfish-diseases.html
97. http://ag.ansc.purdue.edu/courses/aq448/diseases/parasites.htm
98. http://wildlife.state.co.us/Research/Aquatic/WhirlingDisease/Pages/WhirlingDisease.aspx
99. http://en.wikipedia.org/wiki/File:Whirling_disease_pathology.jpg
101. http://www.fishhelpline.co.uk/health/microscopes.html
108. http://www.saltwater-aquarium-online-guide.com/fish-diseases-and-treatments.html
109. http://www.saltwater-aquarium-online-guide.com/fish-diseases-and-treatments.html and
http://www.wetwebmedia.com/blkichf2.htm
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