Toxicity and gross pathology of ivermectin bath treatment in sea bream Sparus aurata, L.

The isopod parasite Ceratothoa oestroides becomes hard to eradicate in intensive fish rearing systems and in addition to causing weight loss in adult fish it causes mortalities in larval and juveniles stages of sea bass and sea bream. Faced with the fast emergence of this infection in Adriatic finfish facilities, an effective compound had to be tested for bath treatment. Ivermectin was chosen for this purpose on the basis of extensive practice in northern European countries which used ivermectin administered in food with good results in treatment of Lepeophtheirus sp. and Caligus sp. infections. For determination of toxicity of ivermectin, a short-term toxicity bioassay on 40-day-old sea bream, Sparus aurata, L., was conducted, following FAO and UNEP procedures for methodology in aquatic toxicity trials. Median survival time, slope functions, and 95% confidence limits for ivermectin showed moderate toxicity in sea bream, with first 100% mortalities during 96 h at the concentration of 1.8 mg/L.