Monthly Prevalence (%) of bacterial diseases
• Bacterial fish diseases are very common and are one of the most difficult health problems to deal with.
• These bacteria are generally saprophytic in nature and only become pathogenic when fishes are physiologically unbalanced, nutritionally deficient, or there are other stressors, i.e., poor water quality, overstocking, which allow opportunistic bacterial infections to take advantage of the stressors in the system
• Bacterial diseases have been frequently encountered in eggs, fry, fingerlings of fish, causing heavy mortality.
• It is caused most commonly by flexibacter columnaris. This is primarily an epithelial disease that causes necrosis and erosions of the skin and gills.
• Infestation of red disease is highest in the month of January (100%), December (98.75%) followed by February, October; lowest in the month of July (72.41%)
• Skin lesions are often noticed at base of the fins, with variously sized areas of haemorrhage necrosis. There are red areas on body, skin ulcers, swollen body abdomen and eyes and musculature hence often called as red disease.
• Columnaris disease is observed in the month of July (55.10%), followed by June (25.0%), August (24.13%) and lowest prevalence of columnaris disease in the month of March (4.16%), November (8.69%).
Monthly prevalence (%) of parasites
• Occurrence of parasitic fauna are due to high stocking density, water depth, temperature along with other physio chemical parameters and management practices maintained in culture systems.
• The infestation by parasites is greatly influenced by the season, which interferes with the ecology and physiology of the fish.
• Highest parasitic frequency index (PFI) was observed in months of June (75.0%), July (65.50%) and lowest in the month of September (1.33%).
• Occurrences of parasitic fauna such as Dactylogyrus sp, ParaDactylogyrus, Myxobolous sp, Argulus sp, were reported from Indian major carps.
• Parasitic frequency Index of Dactylogyrus sp was found in highest in July (55.17%) and lowest prevalence was found in September (13.33%).
• Parasitic frequency index (PFI) of Myxobolous sp were found highest in June and myxobolous was not found in the months of September, October, January, February.
• High prevalence of myxozoan parasites during August to January and lowest prevalence in the month of February.
• Prevalence of Argulus was found in June, July, October and January; ‘0’ % prevalence was observed in August, September, November, December, February, March.
Occurrence of red disease, columnaris diseases, Gill fluke, myxobolous, Argulus are more during monsoon winter than spring & rainy season and hence the farmers are advised to take due preventive and control measures during post rain and winter seasons in grow out culture system.
The prophylaxis and therapeutic control of fish diseases are of utmost importance for the farmers to protect their crop against pathogens.
Besides implementation of better management practices (BMP) it is vital to prevent frequent occurrence of disease and economic loss in aquaculture.
Blogger:
Dr. Sathish Prasad
Senior Scientist – Aquatic Animal Health
Growel Innovation Center,
RS NO.57, Chevuru Village, Sriharipuram Panchayat, Mudinepalli Mandal, Krishna District – Andhra Pradesh India – 521329
Email: [email protected]