fish parasite and disease

8/12/2019 Fish Parasite and Disease

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Fish Parasite and

Disease



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



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.



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.



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



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.



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.



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.



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.



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.



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.



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



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.



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



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.



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.



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fish parasite and disease

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