the following presentation describes the different pathogens present in the aquaculture system that severely affects the fish culture.

1. Fish diseases
Ratul Chakraborty
M.F.Sc. Scholar
Dept. of AAH, FFSc,
WBUAFS
Fish diseases
Ratul Chakraborty
M.F.Sc. Scholar
Dept. of AAH, FFSc,
WBUAFS

2. 1. Fungal disease:
I. Saprolegniasis or cotton wool disease.
a) Causative agent:- Saprolegnia parasitica
b) Symptoms:-
 White to brown cotton like growth.
 Consisting of colonies of mycellium with small to large patches on body.
 Infect the fertilized egg- egg become white and fail to hatch.

3. c.) Diagnosis:
 Microscopic examination reveals the characteristic hyaline and coenocytic
mycelia Numerous sporangia – tentative generic identification.
d.) Prevention and Control:
Bath treatments of chemotherapeutants such as:
• Zinc-free malachite green (67 mg/L for 1 min; 0.2 mg/L for 1 h)
• Sodium chloride (22 g/L for 30 min; 30 g/L for 10 min)
• Formalin (0.4-0.5 ml/L 30% formaldehyde for 1 h)
• Hydrogen peroxide and increasing the salinity

4. II.EUS(Epizootics Ulcerative Syndrome)
a)Causative agent:- Aphanomyces invadans
b)Symptoms:-
 The clinical signs of this disease are Red spot on skin, Restrict feeding, scale become detach,
blood
 hemorrhage on whole entire the body and waste of epidermal tissue, Fish become sluggish and
swim on surface with head out of water etc.Its occur during post monsoon and some where it is
occur during may and February.
c)Treatment :-
 EUS is prevented by natural way by applying lime(dose-10-12kg/acre),and
 turmeric(500gm/bigha).
 another way is medical treatment by applying CIFAX(1ltr/ha/m of water),
 BKC(500ml/ha/m of water),
 Lime(200-250kg/ha),
 Aquacure-FS(1kg/ton body weight).

6. 2.Protozoan diseases
I. Ichthyopthiriasis (white spot disease)
a) Causative agent:- Ichthyopthirius multifilis
b) Symptoms:-
 nodular white spots fins, gills and skins.
 Affected fishes show irritation , erratic movement and restless with
tendency to rub on the sides.
c) Treatment: therapeutic
 Hourly bath in 1:5000 formalin solution for 7 days .
 Bath in 2% sodium chloride solution for 7 days

7. II. Trichodiniasis (cat fish and IMC)
a) Causative agent:- Trichodina reticulata
b) Symptoms:-
 colour of the gills turn pale and there is a creamish coating due to
excessive mucus secretion .
 Heavily infested fishes gradually become sluggish and loss weight.
 Hyperplasia and respiration process also hampered.

8. C) Treatment:- therapeutic
 Sodium chloride bath treatment @2-3% till
the fishes are stressed.
 Potassium permanganate treatment @ 4ppm
in pond.
 Formalin bath treatment@100ppm with
aeration.

9. I. Argulosis
a) Causative agents:- Argulus bengalensis
b) Symptoms:-
 The afflicted fishes are restless with erratic
swimming behaviour and loss of appetite.
 Attachment sites show sign of ulceration
3. Crustacean parasite diseases

10. C) Treatment :-
 Sodium chloride bath treatment @3-5% till
fishes are stressed
 Gammaxene treatment in pond @1ppm
 Pottasium permanganate treatment in
pond@4ppm

11. II. Lerneasis (Anchor worm)
a) Causative agent:- Lernea bengalensis
b) Symptoms:-
 Heavily infected fishes become restless and
rub against the sides and bottom of the pond
due to irritation..
 Heavily infested fishes become moribund
with erratic movement and emaciation

12. C) Treatment :-
Therapeutic
 Potassium permanganate treatment in pond
@4ppm
 Sodium chloride bath treatment @3-5 ppm

13. 4.Bacterial diseases
a. Furunculosis Disease:
• Furuculosis disease is caused by Aeromonas salmonicida in salmon fishes. It is a non-
motile, gram-negative bacterium.
• This disease frequently appears to infect fishes living in the dirty waters containing a
large amount of decaying matter.
• The first symptoms of this disease are appearance of boil like lesions.
• Others symptoms are blood-shot fins, blood discharge from the vent, haemorrhages
in muscles and other tissues and necrosis of the kidney.
• Bursting of boils allow the spread of this disease among other fishes and also offer
suitable areas for fungus growth.
• Fishes severely infected with the bacteria die in good number.
• Remove the severely infected fishes from the pond and supply food containing
antibiotics like sulphonamides or nitrofurans.
• Sulfonamides like sulfadiozine or sulfaguanidine are given orally with food at the
rate of 22 g / 100 kg of fish / day.
• Other antibiotics like chloromycetin and tetramycin are most effective at a dose of
5-7.5g / 100 kg of fish / day. Disinfect the eggs with 0.015% solution of methiolate or
0.185% acriflavin.

15. b. Columnaris Disease:
• Columnaris disease is caused by Chondroccus columnaris and Cytophaga
columnaris in many freshwater aquarium fish.
• It is a long, thin, flexible, gram-negative slime bacterium (myxobacteriales).
• This disease is often associated with low oxygen level.
• Initially it is marked by appearance of grayish-white or yellowish-white patches
on the body.
• The skin lesions change to ulcerations and fins may become frayed.
• Gill filaments are destroyed and eventually lead to the death of the fish.
• Addition of 1 ppm copper sulphate in the pond to control this disease is
effective.
• Tetramycin administered orally with food at a rate of 3 g / 100 pounds of fish /
day for 10 days is very effective.
• Dip treatment in malachite green (1:15000) for 10-30 seconds and one hour
bath in 1 ppm furanase is very effective to control this disease.

17. c. Fin and Tail Rot Disease:
• Fin and Tail Rot disease is caused by Aeromonas salmonicida and A.
liquefaciens. However, protozoans and fungi may also be involved.
• It is characterized by appearance of white lines along the margins of fins,
the opacity usually progresses towards the base eroding them and causing
haemorrhage.
• The fin rays become brittles first and later break leading to the complete
destruction of the fins. The infection may also spread on the body surface.
• Fin and tail rot are associated with poor sanitary conditions in fish ponds
and with water pollution in nature.
• The Fin and tail rot may be checked at an early stage by keeping fishes in
0.5% copper sulphate solution for 2 minutes.
• Control may be achieved with 10-50 ppm tetramycin and 1-2 ppm of
benzalkonium chloride.
• In severe infections the affected parts are surgically removed and the fishes
are then kept in 0.04% potassium dichromate.

19. d. Tuberculosis Disease:
• Mycobacterium is a disease causing agent which is difficult
to diagnose without pathological examinations.
• The symptoms are ulcers on body, nodules in internal
organs, fin and tail rot, loss of appetite and loss of weight of
fish.
• This can be cured with dip treatment in 1:2000 copper
sulphate for 1 minute for 3-4 days.
• Antibiotics are not successful. The fishes should be
destroyed and potassium permanganate or lime used in the
pond.

21. e. Vibriosis Disease:
• Vibrio bacteria are the causative agents of vibriosis disease in
salmon and many other fishes.
• This disease may occur in waters with low oxygen. These
bacteria are small gram-negative bacilli, characteristically
curved.
• Diseased fishes show large, bright coloured, bloody lesions in
the skin and muscles, haemorrhages in eyes, gills may bleed
with slight pressure, and inflammation of the intestinal tract.
• Sulfamethazine at a rate of 2 g / 100 pounds of fish / day
gives good results. 3 – 4 g / 100 pounds of fish / day for 10
days of tetramycin also give satisfactory results.

23. 5. Viral diseases
I. Viral Hemorrhagic Septicaemia (VHS):
• This disease is caused by an unequal shaped fish virus with RNA.
• This disease occurs in salmon fishes. Transmission of the disease occurs
through the water by a flagellates.
• The symptoms are kidney swelling, reduced appetite, obvious distress,
erratic spiral swimming, multiple haemorrhages in skeletal muscles,
change in body colour, reddish fins.
• The only control measure is prevention.

24. II. Infectious Pancreatic Necrosis (IPN):
• This disease is found in trouts.
• This disease causing high mortality of fry, fingerlings and
occasionally larger fishes.
• The symptoms are darkening distension, haemorrhages in
ventral areas including bases of fins. There is pronounced
pancreatic necrosis.
• 200 ppm of chlorine is effective for treatment.

25. III. Infective Haemopoitic Necrosis (IHN):
• IHN was observed for the first time in trouts in British Columbia (Canada)
in 1967.
• Necrosis is observed in the haemopoetic tissue of kidney in infected fish.
• This disease occurs more in fry and fingerlings and occasionally in adults.
• The symptoms are pale gills, reddish fins, black colouration of the body,
abdomen swelling and huge mortality.
• The symptoms are clear in 12-45 days after the entry of virus into the
host body.

26. IV. Channel Cat Fish Virus Disease:
• This disease occurs in fingerling of cat fish (Ictalurus
punctatus).
• The symptoms are that the fish show abnormal swimming and
rotating, haemorrhagic areas on fins and abdomen, fluid
accumulation in abdomen and pale gills.
• There is no treatment for this disease. Destruction of infected
fish may prevent spread of the disease