Evaluating the Lethal Dose (LD50) of Ivermectin for Common Carp: Insights From an Oral Toxicity Study

Ivermectin (IVM) is commonly used for the treatment of parasitic diseases in aquaculture and is administered either through oral or immersion methods, but it lacks regulatory approval.

The aim of the present study was to determine the acute oral toxicity of IVM by estimating the 96 h median lethal dose (LD50) using mortality as endpoint, for an economically important freshwater fish, Cyprinus carpio.

Medicated feed was prepared by employing different doses of IVM top-dressed onto the commercial feed pellets. A single oral dose of IVM at different doses (mg/kg b.wt.) of 0 (control-T1), 1 (T2), 2.5 (T3), 5 (T4), 10 (T5), 12 (T6), 15 (T7), 18 (T8), 21 (T9), 25 (T10), and 50 (T11) was dissolved in dimethyl sulfoxide (DMSO) and top-dressed using 0.5% w/v guar gum as a wet binder to the feed. The medicated feed was administered at 3% b.wt. to all treatment groups and cumulative mortalities were recorded over a duration of 96 h.

The estimated LD50 of IVM was found to be 8.91 ± 3.46 mg/kg·b.wt. Furthermore, the treatment group (T2) was administered a single oral dose of 1 mg/kg b.wt. and did not exhibit any noticeable behavioral changes compared to the control group. Similarly, LOAEL and NOEAL doses were found to be 2.5 mg/kg b.wt. and 1 mg/kg b.wt., respectively.

This study provides valuable insights for further determining the safe dosage of IVM that can be used in aquaculture for the treatment of parasitic diseases.

The present study might be helpful for fixing the maximum residual limit (MRL) for IVM in the aquaculture sector, and the data will be helpful for prescription of the drug by regulatory authorities for treating parasitic diseases in fish.