<div>Background: Triclosan is an antimicrobial agent which enters into the aquatic environment through wastewater discharges which causes potential health risk in human and aquatic organisms. The present study aimed to determine the toxic effects of triclosan on Oreochromis mossambicus. 
 
Methods: The fishes were subjected to five different concentrations viz. 131, 262, 523, 1046 and 2092 &micro;g.l-1 of triclosan for 96 h acute toxicity test. To evaluate the levels of enzymes such as acetylcholinesterase and glutathione S transferase, brain and liver tissues were collected, homogenized, extracted and stored at -20&deg; for further analysis. The DNA damage was assessed in gill and liver tissues using single cell gel electrophoresis method. 
 
Result: In present study, the calculated 96 h LC50 value of triclosan in O. mossambicus was 740 &micro;g.l-1 and the fishes showed various behavioural alterations. Time and dose dependent inhibition of AChE activity in brain tissue was observed during acute toxicity test. However, the GST activity in liver tissue increased on exposure to triclosan with significant increase in concentration of toxicant. DNA damage index was higher in gill tissue compared to the liver tissue during acute exposure to TCS which could cause detrimental effects in fishes.</div>

Short Term Effects of Antimicrobial Agent Triclosan on Oreochromis mossambicus (Peters, 1852): Biochemical and Genetic Alterations