EFFICACY OF OXYTETRACYCLIN AGAINST STREPTOCOCCOSIS INFECTION ON TILAPIA FISH FARMING  

Fish vaccine, immunostimulant and probiotics have been used extensively for fish disease's prevention. But for fish disease's treatment are still relying on chemicals and antibiotics. Uncontrolled use of antibiotics can caused some negative impact, which are can leave residue, disrupting the ecological balance and lead to resistance. The ministerial decree No. 14/2013 states that fish drug such antibiotics must have a registration number. In order to obtain a registration number, manufacturers, distributors and importers must conduct quality tests and field trials. Fish drug's quality test conducted in laboratory, whereas fish drug's field test done by testing out directly to the farmed fish, with method and dosage according to products claims. Oxytetracycline (OTC), an antibacterial agent, is extensively used in aquaculture practices all over the world. Oxytetracyclin efficacy testing activities were carried out as part of fish drug's field test. The purpose of this study was to determined the effectiveness of oxytetracyclin  medication   against streptococcosis in tilapia that is specific to the Indonesian environmental conditions, so it can be used as a basis for policy making.

The test performed on 180 tilapia fish with an average weight of 20-30 gram, which are divided into negative control group, positive control group and treatment groups.The control group and treatment group were exposed to the bacteria S. agalactiae with intra-peritoneal (IP) injection dose of 10⁷ cells / ml, 0.1 ml. When 70% infected fish showed illness symptoms, tilapia fish in treatment group were given oxytetracyclin through diet feed at 75 mg/kg body mass for ten days. Samples were taken for microbiology and histopathology analysis at 0 and 10^th days (10^th day is the last day of the treatment).

The test result showed no clinical sign or gross pathology were observed in the negative control group. Uch signs were observed primarily in the positive control group and treatment group that died when challenged. The diseased fish exhibited abnormal behaviour. Externally, diseased fish had abscesses, skin haemorrhages,  abdominal distention, and eye lession. This test showed that survival rate of negative control group are 100%, positive control group are 20% and treatment group are 56,67%. Based on statistical test with 95% confidence interval shows that the oxytetracyclin treatment significantly reduce the mortality caused by Streptococcus agalactiae infection.