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3.9.2. Bacterial and fungal diseases in carp rearing systems
Unit 3 - Breeding of major carps
3.9.2. Bacterial and fungal diseases in carp rearing systems
- Bacteria can cause diseases either as secondary invaders or as primary pathogens.
- Bacterial diseases in larvae can be broadly classsified as surface ulcerative, acute systemic and chronic granulomatous type.
- Surface ulcerative type of diseases are characterized by haemorrhagic surface ulcers and are normally caused by Aeromonas, Pseudomanas, Vibrios, Flexibacteria, Myxobacteria, etc. Surface ulcerative disease conditions at times develop to acute systemic disease.
- These are characterized by the presence and proliferation of bacteria in internal organs like kidney, heart, spleen, blood and other visceral organs.
- These diseases produce significant necrotic changes in all the affected organs and can cause mortality in a short time scale.
- Bacterial haemorrhagic septicaemia caused by numerous serotypes of Aeromonas hydrophila is a major problem.
Disease agent |
Chemical |
Method |
Concentration/time |
1. Ectoparasitic protozoans |
|
|
|
a. Ichthyophthirius sp. |
Formalin |
Short bath |
60-100 ppm for 30 minutes |
b. Trichodina sp. |
Formalin |
Long bath |
20-30 ppm |
c. Epistylis & Vorticella |
Formalin |
Dip |
200-300 ppm for 1 minute |
d. Ichthyobodos sp. |
Formalin |
Dip |
20-30 pm for 30 minutes |
2. Monogenetic worms |
|
|
|
a. Dactylogyrus |
Organophoshporus pesticides |
Dip |
10 ppm for < 1 minute |
b. Gyrodactylus |
Nuvan, Dipterex |
Long bath |
0.5 ppm for 24 hours |
3. Crustaceans |
|
|
|
a. Lernaea |
Nuvan, Dipterex |
Long bath |
0.5 ppm for 24 hours |
b. Argulus |
Nuvan, Dipterex |
Long bath |
0.5 ppm for 24 hours |
4. Endoparasites |
|
|
|
a. Sporozoans |
Nuvan, Dipterex |
Long bath |
0.5 ppm for 24 hours |
b. Cercaria and metacercaria of digenetic trematodes |
Nuvan, Dipterex |
Long bath |
0.5 ppm for 24 hours |
5. External Mycosis – Saprolegnia |
Malachite green Formalin |
Dip Bath Bath Dip |
60 ppm for < 1 minute 1-2 ppm for 1 hr 50-75 ppm for 30 minutes 100-200 ppm for 1-3 minutes |
6. Surface bacterial diseases |
Proflavine Oxytetracycline & Furnace |
Bath Short bath |
20 ppm 1-5 ppm |
7. Systemic bacterial diseases |
Furazolidone Oxonilic acid Chloramphenicol |
In feed In feed In feed |
50mg /kg fish/day 10mg/kg fish/day 50 mg/kg fish/day |
Heavy mortality of fish seed due to `gas disease’ has been observed on several occasions. The symptoms of the disease are the presence of gas bubbles in gill filaments, heart and blood vessels and also in the gut. The air bladder gets highly distended. The `gas disease’ also referred to as ‘gas embolism’ occurs due to supersaturation of water with either oxygen or nitrogen and is generally encountered in fish nurseries.