ORAL DOSING OF EMAMECTIN BENZOATE ON THE SAFETY, GROWTH, SURVIVAL AND SERUM BIOCHEMISTRY OF Oreochromis niloticus L.

Tilapias are cultured globally and are rising in acceptance as the most important freshwater aquaculture species. Amongst several issues that affect the tilapia production, one critical factor which is often overlooked is parasitic infections and diseases. Parasites have direct effect on the growth, vulnerability to predation, marketability and overlay means for secondary infections. Emamectin benzoate (EB) is an anti-parasitic agent used under the trade name Slice® in some countries under an "Emergency Drug Use" basis for controlling sea lice at the recommended dose of 50 µg EB/kg biomass/day (X) in coastal finfish aquaculture. The effect of EB on the safety, growth, survival and functioning of vital organs of tropical fish are scanty. The present study examined the dietary influences of EB administered to Nile tilapia Oreochromis niloticus at 0 (0X), 50 (1X) and 500 (10X) µg/kg biomass/day for 7 consecutive days. Mortality, behavioural changes, feed consumption, biomass, levels of serum glucose, alanine aminotransferase and creatinine were determined at scheduled intervals as indicators of stress, liver and kidney functioning, respectively.

The dosing trials were conducted in 12 rectangular tanks with 360 healthy O. niloticus (11.80±1.55 cm and 14.40±1.50 g). The top dressed EB-medicated feeds were offered to 7 days acclimatized tilapia as the sole ration for 7 consecutive days during the dosing period. During the post-EB dosing period (45 days), the tilapias were fed with control feed.

There existed significant dose-dependent reduction in the feed intake and tilapia biomass. Mortalities were recorded in EB-feed fed tilapia at 1X-dose [2.23%] and 10X-dose [4.43%] (Table 1). The serum glucose, alanine transaminase (ALT) and creatinine levels of tilapia increased significantly on day 7 EB-dosing, which subsequently reduced with time. On day 45 post-EB dosing, the biomarker levels were significantly high compared to day 0 (Figure 1), indicating the long-term effect of EB. The data on tilapia mortality, reduction in feed intake and growth and elevated serum biomarker levels, except ALT (1X) even on day 45 post-EB dosing, thus, raise queries on the practicality of oral EB-dosing in tropical conditions.