Intensity of Ichthyopthirius multifilis infection in Clarias gariepinus juvenile 24h pre-treatment with Ocimum gratissimum. Key: B: Negative control (Infected, not treated); C: Standard control (infected and treated with 150mg/L chloromphenicol); D: 500mg/L Ethanolic leaves extract of O. gratissimum (ELEOG); E: 1500mg/L ELEOG.