Trophont intensity pre- and post-treatment with O. gratissimum extract in gill. Key: A: Normal control (not infected and not treated); 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.