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I. Copepod parasites
Argulus
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External, fish lice
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primarily a pond problem
visible, flat, move about
2 sucking disks for attachment
Pierce skin with mouthpiece
and feed on blood.
– Large number vs. small
number
– Secondary infections occur
Lernea
– Slender copepods with
anchor attachment (522mm)
– anchor causes tissue
damage
– Secondary infection
Lernea
– Easily identified
– Primarily warmwater
fish
– Egg sacs are very
obvious
Ergasilus
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External
Small (1.5 - 2.5 mm)
Gill parasite
Many fish species
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Only females on fish
Claw like claspers
1 million eggs year
live 1 year
Actheres ambloplitis
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External
Common on catfish
Gill parasite
Attach by leg like structures
Egg sacs
Especially bad on larval fish
II. Trematode parasites
Gyrodactylus
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External, visible
Monogenetic (complete life cycle on fish)
Live young - move readily
No eye spots
Haptor with 1 large pair of hooks and 16 hooklets
Skin irritation but also on gills and fins
Signs are listlessness, frayed fins, flashing, fungus
Heaviest in winter and spring
Dactylogyrus
– Monogenetic
– Lay eggs in water (not as
explosive as Gyro)
– 4 eyespots
– 1 pair hooks, 16 hooklets
Dactylogyrus
– Primarily a gill parasite
– So cause gill damage and
symptoms can be
mistaken for O2 problem
or other gill infections
– Primarily warmwater,
especially cyprinids
Cleidodicus
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External, monogentic
Eyespots
4 large anchor hooks
Lay eggs
On gills is problem
Symptoms looks like O2 problem
Warmwater fish, especially catfish
Digenetic trematodes
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Quite a number are problems
Some internal, some external
Require more than 1 animal host
Sanquinicola in salmonids
» blood fluke
» snails are intermediates
Digenetic trematodes
– Various types of yellow and black grubs
» common in wild but in ponds also
» aesthetic problem only
» don't know why not in text
» snail - fish - bird cycle
III. Protozoa
I. multifilis
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Large ciliated protozoan
Primarily ww fishes but some cw
White color with large horseshoe shaped nucleus
Flash, twitch, flag
Heavily infested fish are lethargic
Skin, gills, fins - penetrate skin so not exactly external
Can be explosive since 1,000 or more from one
At 70-75o life cycle only 3-4 days
» Only free swimming vulnerable
I. multifilis
Chilodonella
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External
Numerous species
Small, oval, colorless, ciliate (faint bands)
Skin, fins, gills
Both warm and cold but primarily warm and under
crowded cond.
– Signs -- listless, off feed, flashing, lie on side
– Easy to control
Chilodonella
Ambiphrya
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Several species
Small urn-shaped ciliate
Ring of cilia at top end and band of cilia in middle
Skin, gills, fins of salmonids and warm water fish particularly bad on bass and catfish - young
– Usually harmless, but if a lot the scopola (attachment
organism) smothers gills.
– Signs -- piping, may look like bacterial gill disease,
redden skin & gills, listless
– Easy to control at this time
Epistylis
– Stalked ciliates
– Usually on skin but also
gills
– Also eggs (fuzzy so can
confuse with fungus)
– Trout, walleyes, catfish,
others
– Signs
» flashing
» secondary infection
Epistylis
Trichodina
– External
– Ciliate - many species
– Saucer shaped, rows of
cilia, especially on margin.
– Skin, fins, gills, activity
» Signs -- flashing, tattered
appearance of fins, white
irregular blotches
» secondary bacterial
problems
Hexamita salmonis
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Octomitus, internal
Tiny flagellate
Colorless (must stain), pearshaped - 8 flagella
Salmon and trout intestines
Irritate gut lining, irregular swimming, yellow intestinal
fluid
– Some question its status as a pathogen.
– Apparently more of a problem when non-prepared foods
fed
Ichtyobodo
– Costia, external
– Flagellate, small,
pearshaped, flickering
flame
– A couple species
– Trout, salmon, ww fish
especially bad on trout
fingerlings and catfish
Ichtyobodo
– Signs
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light bluish - grayish film
lose appetite
flash
crowd bottom - listless
have to examine
microscopically
Henneguya
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Internal
From many species warm and cold water
A myxosporidean
Encysts in tissue
Muscle damage, but some stages on gills so
No control
Ceratomyxa shasta
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Internal myxosporidian
Salmonids
Has caused many epizootics of 100% mortality
Intestine and gall bladder, spleen, liver, and kidney
Signs
» vent area swelling
» distended abdomen
» early are listless, off food, seek slack water
» fish may darken
– No treatment - transmission method unknown
Myxosoma cerebralis
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Internal myxosporidian protozoan
Twisted spines and deformed backs
Salmonids
Whirling or tail chasing is a sign "called whirling
disease"
– Survivors often deformed and have "Blacktail" (loss of
chromatophore control)
– No known control method except prevention
– Really a problem in young fish
Plistophora
– Internal
– Several species
– Small (3-6 microns)
beanshaped
– Trout gills, golden
shiner ovaries
(reduces fecundity)
– No control
Plistophora
Cryptobia borreli
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Flagellate
Variety of fishes including salmonids
A blood parasite, affects kidney function
Signs
» anemic
» popeye (exophthalmic)
» fluid in body cavity
– No treatment
IV. Fungal disease
Fungal disease
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Pervasive
Numerous species including Saprolegnia
Fish and eggs
Warm, cool, cold
Appears as a white cottony growth on eggs on fish is white
to brownish patches on various body areas
– Any damage to body surface can open way, spawning,
netting, handling
– Control by sanitation, or chemicals, for others no control
– Often prophylactic type treatment of eggs
Saprolegnia
V. Bacterial disease
Furunculosis
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Aeromonas salmonicida -- Salmonids
Cause muscle lesions
Can enter through scratch or digestive tract
Bacteria produces a toxin
Signs
» blisters or patches - bluish - red or purple
» hemorrhages at fin bases or frayed dorsal fins
» acute lesions
– Short incubation
Furunculosis
Pseudomonus
– Also called fin rot
– Signs
» superficial grayish - red skin ulcers
» dropsy
» popeye
» inflamed fins
– Many fishes affected - frogs also
– Much different than fin rot
– Warm and cold
– Variety of symptoms
Cytophaga psychrophilia
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external
Usually called peduncle disease
A low water temp. disease
Signs
» darkening
» lesions on peduncle or near pectoral fins
– Worst on young fish
– Can result in total erosion of caudal area
– Primarily a problem in 40-50oF range
Yersinia rucheri
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Causes enteric redmouth disease in salmonids
Inflammation and erosion of jaws and palate
May kill more RBT than any other bacterial agent
Signs
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black, popeye
lethargic, drift at surface
mouth and tongue inflamed, underbelly with spotty hemorrhages
dead fish with dropsy
fin sockets hemorrhaged, in heavily infected fish - gill bleeding
– Especially a problem in intermountain west and still growing
– Worst in hot summer months
Bacterial Gill Disease
– external
– Called GD often
– Salmonids and warm water (but primarily
salmonid)
– Superficial infection of gill epithelium
– By an undecided bacteria, probably related to
columnaris disease causative agent
Bacterial Gill Disease
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Above 56o becomes more of a problem
Fish can't get rid of CO2 and ammonia or get O2
Often secondary fungal infection
Signs
» lethargic, off food, pipe, "ride high"
» whitened gill tips, excess mucous
– Worse in fingerlings
Flexibacter columnaris
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external and internal
Columnaris disease
Through skin and gills, especially if scratched
Seldom a problem below 55oF worse at 65oF
Primarily salmonids and catfish
Signs
» grayish white body lesions with bright yellow
slime
» common on head and mouth
» internal also
Hemophilus piscium
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internal
Ulcer disease
Ulcers or sores on surface of fish and work inward
Resembles furunculosis but opposite sores work
in but in furunculosis work out
– Circular sores
– Salmonids primarily
Tuberculosis
– Related to human tuberculosis bacterium
– Salmonids
– Almost no problem now since don't feed fish
viscera products
– External and internal lesions
– kidney, spleen, liver, digestive tract
Tuberculosis
Vibrio anguillarum
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internal
Called Vibriosis
Many fish
Primarily a problem of marine cultured fish
Signs
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off feed
lethargic
erratic swimming, spinning
bloody discharge from vent
internal
Renibacterium salmoninarium
– internal
– Causes kidney disease
– Salmonid problem
– Kidney lesions but can develop into
musculature fluid in body cavity, dropsy
– Really a lot not known about this and is a
real problem
VI. Viral diseases
Infectious Pancreatic Necrosis
(IPN)
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Salmonids, NA & Europe
High fingerling loss
Over 6 in. are carriers
Signs
» death rate up for healthy looking fish in fact some of best
looking die first
» some spiral and roll
» tail chasing, darkening, popeye, dropsy
» internal also
– A small pathogen
– June and July worst months
Viral Hemorrhagic Septicemia
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Primarily Rainbow Trout
Not bad on fry or adults - middles ones worse
Not egg transmissible but
Signs
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color, popeye
hemorrhage at fin bases
lethargic, seek edges
internal also
– Late winter, early spring
Infectious Hemapoietic Necrosis
(IHN)
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Rainbows and some other salmonids
Not egg transmissible but a lot not known
Ovarian fluid can do it
Signs
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flagging
dark, lethargic, popeye
hemorrhaging tissue near vent and fins
pale gills
internal also
– April to June
Channel Catfish Viral Disease
– CCVD, CCV
– Signs
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when temperature reaches 70oF sudden increase in death
spiralling or swimming abnormally
convulsions
just before death at surface with tail down
fin base hemorrhage
internal also
– Often obscured by columnaris
– Appears to be host specific for catfish
Lymphocystis
– Many fish but walleyes and centrarchids worse
– Mostly aesthetic, chronic
– Abnormal growth of connective tissue - wart like
Lymphocystis