Major Fin Fish Diseases, Their Symptoms and Management Measures

Subhendu Datta & Pavan Kumar Central Institute of Fisheries Education, India

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Major Fin Fish Diseases, Their Symptoms and

Management Measures

Introduction

In recent years traditional aquaculture has turned into a science based

economic and commercial activity involving heavy inputs and therefore, diseases of all

kinds are known to occur on an increasingly large scale. However, fish mortality is not

the only criterion to evaluate the effect of fish disease. Even the morbidity which leads

to weight losses and poor growth in surviving fish contributes substantial losses to the

farmers. With increasing intensification of fish culture we are faced with an increasing

number of recognized infectious diseases due to ever changing environment.

Therefore, research on the pathogenesis and pathology of these diseases, their

prevention and control has become essentially required.

Water Quality – Why Is It Important?

Fishes are poikilothermal aquatic animals and need continuous acclimatization to the

environmental changes. To a great extent, the success or failure of fish culture is

determined by water quality. A Successful pathogen must first find a susceptible host

for its lodging and multiplication. It is not easy. Because the body of fish is covered

with scales. Mucus secreting epidermal cells. Easier way is to get entry into host is a

lesion on the skin or through other openings like mouth, eyes, nostrils.

Stressors for fish:

The stressors which elicit morphological and physiological responses in fish fall

into 4 categories.

Chemical - Stress due to water quality, pollutants, and metabolic wastes.

Physical – Temperature and super saturation of gas

Procedural – Stress due to handling, transportation, stocking or disease treatment.

Biological – Stress due to population density, confinement, diet composition and

micro- and macro-organisms.


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A fundamental management objective of all fish rearing practices is to avoid and

minimize stress on fish.

Stress: The aquatic environment is dynamic and constantly subject to changes in

its physical, chemical and biological components. These changes along with

culture practices – stressors severely stress the physiological systems of fishes.

The physiological response elicited initially is adaptive. However, they may

ultimately become maladaptive in chronic situations.

Stress response

Most fish diseases are stressed mediated. Stress is a physiologic state caused by a

procedure, environmental condition or other factor which interferes with the fish’s

ability to maintain a “normal” state. It extends the adaptive responses of an animal

beyond the normal range or which disturbs the normal functioning.

Bacterial Diseases

Innumerable diseases are caused in fishes due to bacterial pathogens and

several of them are reported in Indian literature. They occur in nursery, raering and

grow out ponds causing serious concern to fish farmers. Some of them often wipe out

the entire population of fish. Some of the important bacterial pathogens are

Aeromonas hydrophila, A. salmonicida, Pseudomonas fluorescens, P.putrefaciens,

Flexibacter columnaris, Edwardsiella tarda, Vibrio alginolyticus and V.

Stress

Perceived by CNS

Stress hormones Cortisol and epinephrin released from interrenal cells into blood stream.

Blood and tissue alterations

Reduction in growth and resistance to diseases

2o response -

3o response -


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parahaemolyticus which have been identified as the most commonly encountered

agents in fish diseases.

Fin rot and tail rot

Fin rot and tail rot in hatcheries, nurseries and grow out ponds have been

reported in young and adult fishes. The disease is contagious and is capable of

causing immense damage. Fin and tail rot in young fish are due to a mixed infection of

A.hydrophila and Pseudomaonas fluorescens. Control measures adopted are bath

treatment in 1:2000 copper sulphate for 2 minutes or swabbing of concentrated copper

sulphate solution in the affected fishes.

Dropsy

Dropsy is frequently encountered in carps like Catla, rohu and mrigal mostly in

composite culture ponds in late winter. The epidermis and body cavities get filled with

fluid and scales protrude out from their pockets leading to severe anaemic condition. A

mixed infection of A. hydrophila and myxozoan parasite or malnutrition is frequently

the cause of infectious dropsy in Catla.


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The affected fishes could be effectively treated by Terramycin in the feed. Application

of neem leaf and leaf extract in the pond water, lime in soil, change of pond water with

fresh water can control this disease within 2/3 days.

Eye disease

A. liquifaciens infects the eyes of rohu, catla and silver carp. The cornea of the

eyes gets vascularized leading to opacity and complete necrosis and even mass

mortality of fish has been recorded. Investigations have isolated Staphylococcus

aureus from the affected eyes of diseases fish. Chloromycetin bath @ 8 - 10mg/L has

been found effective in controlling the disease at an early stage. Disinfecting the

environment with Potassium permanganate at a dose of 0.1 ppm followed by liming

@300 ppm check the disease.

Ulcerative disease

Bilateral ulcerations of the opercula and the head in catla are observed in

ulcerative disease. In most cases, A.hydrophila could be isolated, although several

other bacterial forms were also present as secondary invaders.


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Columnaris disease

Cause external lesions over the body surface. The causative organism has

been identified as Flexibactercolumnaris. Topical application of potassium

permanganate or short bath in 500ppm of Potassium permanganate has been found

to be very effective in completely curing the disease.

Edwardsiellosis

It is a septicaemic disease affecting brood fish population. Edwardseilla tarda

has been isolated from the diseases fish showing anaemia, cutaenous lesions and

gas filled abscesses in the muscle. Although treatment with idophor has been found to

be effective, water quality improvement in the hatchery is the most essential

component for keeping the disease away.

Epizootic ulcerative syndrome (EUS)

Epizootic ulcerative syndrome (EUS ) has ecome a matter of great concern not

only among fisherman and fish farmers, but also among general public

,entrpreneurs,administrators and planners. One common feature of the disease is that

it initially affects the bottom dwelling species like murrels followed by catfishes, weed

fishes and IMC. The lesions start as small grains to pea sized haemorrhagic spots

over the body which ultimately turns into big ulcersof the size of a coin with grayish

slimy central necrotic areas surrounded by a zone of hyperemia. The disease affects

to such an extent that they starts rotting while still alive and eventually die. A number

of bacteria viz.A.hudrophila, A.punctata, Flavobacterium sp., Pseudomonas sp.,

Edwardsiella tarda, Vibrio parahaemlyticus and Streptococcos sp. have been

isolated from the affectd specimens. Histopathological studies revealed complete loss

of epidermis in the ulcerative area of the skin where the dermis and hypodermis

showed characteristic granulomatous changes. Besides bacteria, virus, fungus and

parasites were also reported to be associated with EUS,


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Many antibiotics, sulfonamides, chemicalsherbal preparations etc. have been

advocated as preventive and curative measures. Lime was accepted widely among

fish farmers of the country until the formulation of CIFAX, therapeutics developed by

Central Institute of Freshwater Aquaculture (CIFA). Marked improvement of the

ulcerative condition is noticed within seven days of application of the medicine and the

ulcers are healed up with in 10 -14 days.

Protozoan diseases

Ichthyophthiriasis

The white spot disease or Ichthyophthiriasis is a common disease of fresh

water carps. Affected fishes exhibit minute white nodular spots on the skin, fins and

gills and are restless. The causative agent is Ichthyophthiriasis multifilis. This parasite

can be controlled by hourly bath treatment for 7 days in 2-5% NaCl solution. Pond

treatment advocated is application of 15-25mg/L formalin.

The protozoa: Ichthyophthiriasis multifilis


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A = The trophozoites in the host's skin.

B = Trophont leaving the host.

C = The mature trophont with hundreds of maturing tomites.

D = The releasing of tomites that penetrate the skin of the host fish.

A = The cycle continues all over again.


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Trichodoniasis

Various life stages of IMC and cat fishes are affected by the parasites. The

csusative agents are urecolariid ciliate species of the genus Trichodina,Tripartiella

and Trichodinella. They attach to the fish gills by means of adhesive disc constituted

by skeletal elements. The treatment methods adopted are water quality improvement,

diminishing stocking density of fish, bath treatment of fishes with 2-3% NaCl or 50

mg/L KMnO4 and pond treatment with 5 mg/L KMnO4 or 25 mg/L formalin.

Trichodina, circle shaped skin Parasite on Gill filament

Coastiasis

Heavy infestations of the genus Coastia (Ichthyoboda) causes the disease. It

infests the gills and external surfaces of all species of fresh water fishes and is

reported to proliferate at low temperature (250c) . The affected fishes show grayish

white shade on the body surface. These parasites are controlled by bath treatment of

fishes with 2-3% Nacl or 50 mg/litre KMno4 and pond treatment with 5mg/litre KMno4

or 25mg/litre formalin.


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Myxosporean disease

Myxosporidia are one of the most important groups of pathogens capable of

producing diseases in fish causing heavy loss on the juvenile. Myxobolus cysts of

varying sizes have been reported on the gills and kidneys of Catla catla. Larger cysts

are located at the distal end of the gill filament whereas smaller ones are seen at the

proximal end. Infections damage the respiratory surface of the gill and excretory

tubules of the kidney. Diagnosis of the diseae can be made on the basis of gross

appearance of the pin head sized grayish cysts and large number of myxosporidian

spores under the microscope.

Helminthic parasites

Dactylogyrosis and Gyrodactylosis

Fishes are infected on their gills and skin by monogenetic and digenetic

tremetodes. The important monogenetic species belong to gyrodactylus (Skin fluke)

and dactylogyrus (Gill fluke). They remain attach to the skin (gyrodactylus) and gills

(dactylogyrus) by the help of anchors which causes wounds. Their presence cause

hyper secretion of mucous and haemorrhage from blood capillaries. These wounds

later get infected with pathogenic bacteria and fungi. Alternate bath in 1:2000 acetic

acid solution followed by bath in 2% sodium chloride solution has been found

effective. Some workers have advocated dip treatment in 5% solution followed by a

bath in 1:5000 formalin.

Dactylogyrus


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Gyrodactylus –body fluke


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Black spot disease

The digenetic trematodes generally infect the alimentary canal, but are rarely

harmful. However, in the metacercarial stage they are harmful as they get encysted in

any part of the body. i.e. skin, muscle, abdominal cavity, liver ,eyes, and brain. In

these cases fish serves as intermediary host , while the final host is generally a fish

eating bird. In many carp fingerlings the black spot disease is due to metacercaria of

Diplostomatidae.

Life cycle of Diplostomum

Ligulosis

IMC in reservoirs and lakes are affected by this disease. Diseases fishes are

dark colour anaemic and abdomen is distended because of large number of parasites

at infective stage.The causative agent is the plerocercoid stage of the parasite Ligula

intesinalis. Control methods are limited to extermination of the definitive host, the

ichthiophagous birds. Interestingly, the fish is not the major host of Ligula; the cycle

starts in the body of birds. The life expectancy in the major host is a maximum of 5

days, but in this time they will lay a multitude of eggs. These eggs are passed into

water via the faeces of the bird. Once in the aquatic medium they hatch and are eaten

by a wide range of copepod zooplankton. The cycle continues when the fish ingests


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the copepod. The worm then burrows through the gut wall and continues to develop in

the fish's body cavity. The cycle is then complete when the bird eats the tapeworm

hosting fish.

Acanthocephalan disease

IMC, cat fishes and many other fishes are parasitized by these helminthes.

These parasites inhabit the alimentary tract of fishes attaching themselves by their

probiscs. The attachment site of the intestinal epithelia gets damaged and become

focci for secondary infection. The causative agents are acanthocphalans,

Acanthogyrus acnthogyrus, A.pallisentis sp. Proper treatment methods have not

developed.


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Crustacean parasites

Argulosis

IMC are mostly affected by this parasite. The causative agent is the

branchiuran parasites Argulusfoliaceus (Fish lice), A.bengalensis. The nauplius

and other developmental stages which are free living are parasitic to the host fish.

Attachment site of parasites shows signs of ulcerations, growth retardation and

occasionally mortality occurs. Argulus must be eradicated quickly as the parasite

causes considerable physical damage to the skin which often results in

subsequent ulcerations of the affected areas if left untreated. It is controlled by

bath treatment with NaCl @ 3-5%, Pond treatment with KMnO4 @5mg/ litre,or

mechanical removal of Argulus sticky eggs by hanging bamboo mats or corrugated

sheets in the water area and its removal and drying in the sun after a week for

killing the eggs.


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Fish lice are flat, disc-shaped parasites which attach themselves to fish with small

suckers. They feed on blood and tissue fluids by piercing the skin with sharp

mouthparts.

Ergasilosis

Infestation occurs in gills, buccal cavity, operculum and gills. The

causative agent is the species of genus Ergasilus. The parasites are controlled by

pond treatment with potassium permanganate @ 5mg/L or bath treatment of affected

fish with 2-3% NaCl.

Ergasilus

Lernaeosis

Heavily infected fishes become moribund with erratic movement and

emaciation. Attachment areas on host exhibit sloughing off and ulceration. The

causative agents are Lernea chackoensis, L.bengalensis (anchor worm). The

parasites are controlled by the same treatment as for Ergasilus sp.


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Fungal Diseases

Saprolegnia

Saprolegnia parasitica infection in the fry and fingerlings of major carps is one

of the main problems affecting health of fishes. The disease in fish is characterized by

a white to brown cotton like growth consisting of colonies of mycelium and filaments

which appear as small to large patches on various parts of the body like fins, gills,

mouth, eyes or muscle. The infection starts due to netting injury and over crowding or

lesions caused by other diseases.

Saprolegnia infection on the body of a koi

Branchiomyces

Branchiomyces is another problem causing 'gill rot '.


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Diseases and control measures for Indian Major Carps Catla Catla(Source:FAO)

In some cases antibiotics and other pharmaceuticals have been used in treatment but their inclusion in this table does

not imply an FAO recommendation.

DISEASE AGENT TYPE SYNDROME MEASURES

Eye disease Aeromonas liquefaciens Bacterium

Eye, optic nerves and brain affected;

cornea of eye vascularised & becomes opaque;

subsequently eye ball gets putrefied,

leading to death

Treat affected ponds with 0.1 ppm

KMnO4, followed by

300 ppm lime

Ulcer Aeromonasspp.;Pseudomonasspp. Bacteria

Ulcerations;

exophthalmia; abdominal distension

Destroy badly

infected fish; disinfect affected

ponds with 0.5 ppm solution of KMnO4; add sulphadiazine

(100 mg/kg) or

terramycin (75-80

mg/kg) to feed for 10-12 days

Columnaris Flavobacterium columnaris Bacterium

Raised white

plaques, often with reddish peripheral

zone leading to haemorrhagic spots

on body

Dip treatment with

500 ppm KMnO4

Dropsy Aeromonas sp. Bacterium

Body scales stretch

out resembling pine cone; inflammation;

ulceration; exophthalmia; abdominal distension

Disinfect affected

ponds with 1 ppm KMnO4; dip treatment of 5 ppm

KMnO4 for 2 minutes

Saprolegniasis Saprolegnia parasitica Fungus

Mould grows like cotton wool on body,

penetrating into the muscle; morbid muscle rot

3-4% NaCl bath;

KMnO4 bath for 5 days at 160 mg/litre bath for five days; 1-

2 mg/litre malachite

green bath for 30

minutes to 1 hour; add formalin at 20 ml/litre to affected

ponds

Branchiomyosis

(gill rot) Branchiomyces demigrans Fungus

Fungus grows out

through gill blood vessels and causes

necrosis of surrounding tissues;

yellow-brown discolouration & disintegration of gill

tissues

Addition of quick

lime (50-100 kg/ha) to affected ponds; in

case of limited infections, use 3-5%

NaCl bath for 5-10 minutes, or 5 ppm KMnO4 bath for 5-10

minutes

Ichthyophthiriasis Ichthyophthirius multifilis Parasite(protozoan)

Skin, fin rays & operculum covered with white spores;

sick fish keep rubbing against hard

substratum

Dip in 1:5 000

formalin solution for 1 hour for 7-10 days

or in 2% NaCl for 7-10 days; affected

ponds should be disinfected with quicklime at 200

kg/ha


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Trichodiniasis Trichodina reticulata; T. negre Parasite(protozoan) Invasion of parasites

in skin & gill region

2-3% NaCl bath for

5-10 minutes or 4

ppm KMnO4 batch for 5-10 minutes;

treat affected ponds with 25 ppm formalin

White gill spot

disease

Thenohanellus catlae; Myxobolus

bengalensis; M. catlae; M.

hosadurgensis Parasite(protozoan)

Weakness;

emaciation; raising of scales along their posterior margins;

scale loss; perforation of scales;

loss of

chromatophores

Reduce density; add yeast to feed (1

g/kg); 2-3% NaCl bath

Dactylogyrosis and Gyrodactylosis

Dactylogyrusspp.;Gyrodactylusspp. Parasites(monogenean

trematodes)

Gill, fin & skin affected; excessive mucus secretion

3-5% NaCl dip treatment for 5-10

minutes; 100 ppm

formalin bath; treat affected ponds with

25 ppm formalin or 4 ppm KMnO4

Black spot or Diplostomiasis

Diplostomum pigmentata Parasites (digenean trematode

Black nodules due to metacercarial cysts in

the host body; infects eye and causes blindness

Remove resident molluscan population

Argulosis Argulus sp. Parasite (crustacean)

Parasites visible to

naked eye attached to head & fin rays;

haemorrhagic spots found in chronic cases

Drain and dry ponds

showing severe Argulus infection; short duration 5 ppm

KMnO4 dip; treatment with

'Butox' three times at

35 ml/ha-m at weekly intervals

Epizootic Ulcerative

Syndrome

Aeromonas hydrophila; A. sorbia;

Aphanomyces invadans Bacteria and fungus

Large red or grey

shallow ulcers with

necrotic areas on skin; fungus extends

deep into the musculature; lesions

of acute dermatitis and ulcers

200 kg/ha quicklime or 0.1 ppm CIFAX (a

CIFA, India formulation)

Major Fin Fish Diseases, Their Symptoms and Management Measures

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