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8/12/2019 Fish Parasite and Disease
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Fish Parasite and
Disease
8/12/2019 Fish Parasite and Disease
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Parasitic Disease
The term parasitic is a general
term which can include any
micro organism, but in fishpathology it is often restricted
to protozoan (single cell) micro
organisms, nematodesmonogenetic or digenetic
trematodes, or parasitic
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Bodies of inland water such as
lakes ponds streams, rivers,swamps, etc can be characterized
by their parasitic. Ecologically,
parasites of fishes are oftenlimited to particular species of
fish. Their environment is
characterized to a considerableextent by the particular hosts to
which they are associated.
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Environmental factors external ofthe fish host play a major role in
the survival and success of itsparasite to parasites.
Sunlight, temperature, pH,
salinity, oxygen are some of theimportant hysico-chemical factors.For example a moderate gill
infestation with the parasitesichthyophthirius may be toleratedwell if the oxygen level is below5ppm.
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Similarly high levels of ammonia,
extremes of pH, or low level
toxicants may compound the
damage already caused by the
parasites. Regarding biotic
factors, predators, intermediate
hosts, food habits, improper
waste disposed are necessary for
transmission. Frequently these
environmental stressors play a
deciding role in the out come of a
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Parasitic Crustaceans
Parasite- Learnaea (anchor worn) Hosts- silver carp, common carptilapa
Description- the females if these
parasites have a long body withanchor like appendages at the heads.
It reaches a length of about 20mm, not
including the appendages. By meansof their appendages the adult females
parasite sticks to the fish. The males
do not attack fish and is rather
different in shape.
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Transmission- Reproduction of the
parasite takes place in may, two egg
sacs are formed at the end of thefemale’s body which reach a length of
about 3mm from the eggs so called
nauplius larvae hatch. The larvae
swim freely through the water for
some time till they med a fish. The
adults still preying in their host die at
the end of may, leaving large holeswith round opening in the muscles and
skin of the fish.
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Sign- There is usually a servere
inflammatory reaction at theattachment site and secondary or
fungal infection is common and in
many cases may be the cause of
death. Heavily infection fish quicklylose their stamina and strength. If the
parasites attack near nerve centers,
such as the brain or lateral line the fishmay exhibit abnormal behavior.
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Control- since the anchor penetrates
deep under the skin into muscles, thefish becomes badly injured. It is
impossible to remove the parasites
simple by means of forceps; in doingthis serious wounds would be caused
open to bacteria and fungus infection.
Such treatment would be worse than
effect of the attacks of the parasites.
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Parasite- Argulus (fish louse)
Hosts- Japanese ornamental carp
Description- The fish louse is aflattened creature, about as large as a
water flea. The little animals has eight
legs, with which it can swim throughthe water, and a small fish-like rail
which acts like a rubber. The
reproduction and breathing organs aresituated in the rail. There are too large
suckers for attaching to the skin of its
hosts.
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Transmission- The fish louse can only
be introduced into aquaria withsupplies of daphnia or other living
food, obtained from water in which
fishes are present.There is but a very
small chance of capturing a free
swimming fish louse, since this is only
possible if this parasite is in search of
a new host or if it has left its host forthe purpose of reproduction.
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Sign- Through its piercing organ it inject
a toxic substance, causing secondary
severe irritation and scores, and maycarry bacteria thus causing secondary
infection fungi may also secondarily
infect the wounds. Control- As the fish louse is quite a large
creature the parasites may be removed
easily by means of a pair of forceps its
you take the fish in your hand. If thereare two many of them they can be
removed by rubbing over the skin of the
fish always going from the heads to the
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Parasite- Ichthyophthirius
Host- Milkfish tilapia
Description- The organism may be roundor near round. Occasionally a cl- shapednucleus can be observed. Small pearshaped forms seen only with the
microscope are invasive forms called“tomites” the body bears a large numberof cilia over the whole surface areas bythe movement of which the parasite can
swim through the water and penetrateinto the skin of a fish. It has a tubularmouth, several vacuoles and a largenucleus.
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Transmission- the nature, which is
seemed as a white spot, is encysted
just under the skin of the fish.Eventually the adult parasite leaves
the fish and becomes a free swimming
form for about 5,2-6 hr, after whichtime it attaches to any suitable
substance (rocks, plants). The cyst
them undergoes multiple fissions
forming young forms called “tomites”.
Large adult forms have produced up
to 2000 tomites. The development of
nature tomites can be completed
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Sign- The disease cause by this
parasite is called ichtyophthiriasis. It isalso called white spot or “ich”
characterized by the appearance of
greater or smaller number of “spots”of a white or grayish color. Each spot
is in reality or small bladder,
containing one or more parasites that
are rotating in lively fashion.
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Control- Treatment of the
ichthyophthirius is difficult because of
the variability of the time and
completion of the life cycle. One
successful method is to place the fish
in shallow, swiftly moving water,removing dead fish promptly and
sweeping the bottom of the raceways
or ponds daily. This method removesthe nonencysted trophozoites as they
leave the fish as well as tomites.