USE OF DRUGS

In spite of best management practice adopted in the hatcheries and grow-out ponds, disease outbreak may occur, and we may have to use drugs for controlling these diseases. Although some drug have been advocated for treatment of diseases, drugs should be employed only as a last option, since the art of disease control in aquaculture is in the early phase of development. various aspects of using drugs for disease control such as their dosages, intervals of drug administration, duration of exposure of shrimps to drugs, their effect on shrimps, their efficiancy in controlling the disease, withdrawal period from the tissues, their impact on the environment, etc. are yet to be clearly understood. The disease control measures using drugs would be useful only if they are applied during the early phase of the disease. Hence, right diagnosis of diseases at an early stage is a very important aspect that will aid in taking measures to control the disease. Drugs useful in aquaculture

Drug	Purpose	Therapeutic dose and duration	Mode of application	Precautions
Formalin	Ectoparasitic infections	150-250 ppm for 1 h 20 ppm for 12 h 50-100 ppm for 4 h in ponds	Bath	Formalin has deoxygenating effects. Use aeration during treatent. Shrimps with gill infections should be treated carefully since it affects availability of oxygen.
Potassium	Ectoparasitic infections	1-5 ppm for 1 h repeat if needed after 2-3 days 1000 ppm for 10-40 sec. 2 ppm in ponds	Bath Dip	In muddy waters not effective
Copper sulphate	Ectoparasitic infection	0.1 ppm		High doses toxic to shrimps. After treatment, excess CuSO4 can be removed from water by using 3 g/l activated carbon, followed by increased water exchange.
Benzalkonium chloride	Disinfectant, externalbacterial infections (shell disease, necrosis of appendages, black gills) symptomatic treatment	10 ppm for 5-10 min. 5 ppm for 30 min. 2 ppm for 1 h 0.1-0.5 ppm as prophylacyic	Bath Bath Bath	Lower dose preferred
Iodine compounds	Disinfection of eggs and broodstock	3 ml/l for 10 min.		may be toxic to unfertilized ova. Rinse thoroughly after treatment.
Ethylenediamine tetra acetic acid (EDTA)	Vibriosis	5-10 ppm for 12 h Repeat if needed after 2-3 days
Oxytetracycline	Bacterial diseases including systemic infections (Vibriosis septicaemia)	5-10 ppm via feeds (1.5g antibiotic/kg feed, fed at 2-10% biomass) for 10-14 days		Use only during initial stages of disease at right dose only after ascertaining the antibiotic sensitivity in-vitro. Allow 35-40 ays withdrawal period.