Major Fin Fish Diseases, Their Symptoms and Management Measures

Major Fin Fish Diseases, Their T heir Symptoms 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. 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. Subhendu Datta & Pavan Kumar

Central Institute of Fisheries Education, India

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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

Stress Perceived by CNS Stress hormones Cortisol and epinephrin released from interrenal cells into blood stream. 2o response -

Blood and tissue alterations

3o response - Reduction in growth and resistance to diseases 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

Subhendu Datta & Pavan Kumar

tarda,

Vibrio

alginolyticus

and


V.

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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, bacteria, virus, 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 disease d iseases s

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 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 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 KMno 4 and pond treatment with 5mg/litre KMno4 or 25mg/litre formalin.



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Myxosporean 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 Subhendu Datta & Pavan Kumar


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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 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 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 parasites which attach themselves themselves to fish with with small 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) (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

Eye disease

Ulcer

Columnaris

Dropsy

Saprolegniasis

Branchiomyosis (gill rot)

AGENT

TYPE

Aeromonas liquefaciens

Aeromonasspp.;Pseudomonas spp.

Flavobacterium columnaris

Aeromonas sp.

Saprolegnia parasitica

Branchiomyces ranchiomyces demigrans

Ichthyophthiriasis Ichthyophthirius multifilis


SYNDROME

MEASURES

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

Bacteria

Destroy badly infected fish; disinfect affected ponds with 0.5 ppm Ulcerations; solution of KMnO 4; exophthalmia; add sulphadiazine abdominal distension (100 mg/kg) or terramycin (75-80 mg/kg) to feed for 10-12 days

Bacterium

Raised white plaques, often with reddish peripheral zone leading to haemorrhagic spots on body

Dip treatment with 500 ppm KMnO4

Bacterium

Body scales stretch out resembling pine cone; inflammation; ulceration; exophthalmia; abdominal distension

Disinfect affected ponds with 1 ppm KMnO4; dip treatment treatment of 5 ppm KMnO4 for 2 minutes

Fungus

3-4% NaCl bath; KMnO4 bath for 5 days at 160 mg/litre Mould grows like bath for five days; 1cotton wool on body, 2 mg/litre malachite penetrating into the green bath for 30 muscle; morbid minutes to 1 hour; muscle rot add formalin at 20 ml/litre ml/litre to affected ponds

Fungus

Fungus grows out through gill blood vessels and causes necrosis of surrounding tissues; yellow-brown discolouration & disintegration of gill tissues

Parasite(protozoan)

Dip in 1:5 000 formalin solution for Skin, fin rays & 1 hour for 7-10 days operculum covered or in 2% NaCl for 7with white spores; 10 days; affected sick fish keep ponds should be rubbing against hard disinfected with substratum quicklime at 200 kg/ha

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


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Trichodiniasis

White gill spot disease

Dactylogyrosis and Gyrodactylosis

Black spot or Diplostomiasis

Argulosis

Epizootic Ulcerative Syndrome

Trichodina reticulata; T. negre

Thenohanellus catlae; Myxobolus bengalensis; M. catlae; M. hosadurgensis

Dactylogyrus spp.;Gyrodactylus spp.

Diplostomum pigmentata

Argulus sp.

Aeromonas hydrophila; A. sorbia; Aphanomyces invadans


Parasite(protozoan)

2-3% NaCl bath for 5-10 minutes or 4 ppm KMnO4 batch Invasion of parasites for 5-10 minutes; in skin & gill region treat affected ponds with 25 ppm formalin

Parasite(protozoan)

Weakness; emaciation; raising of scales along their posterior margins; scale loss; perforation of scales; loss of chromatophores

Gill, fin & skin Parasites(monogenean affected; excessive trematodes) mucus secretion

Reduce density; add yeast to feed (1 g/kg); 2-3% NaCl bath

3-5% NaCl dip treatment for 5-10 minutes; 100 ppm formalin bath; treat affected ponds with 25 ppm formalin or 4 ppm KMnO4

Parasites (digenean trematode

Black nodules due to metacercarial cysts in Remove resident the host body; infects molluscan population eye and causes blindness

Parasite (crustacean) (crustacea n)

Drain and dry ponds showing severe Parasites visible to Argulus infection; naked eye attached to short duration 5 ppm head & fin rays; KMnO4 dip; haemorrhagic spots treatment with found in chronic 'Butox' three times at cases 35 ml/ha-m at weekly intervals

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)


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Major Fin Fish Diseases, Their Symptoms and Management Measures

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