PROTECTIVE EFFICACY OF CLINACANTHUS NUTANS ON YELLOW-HEAD DISEASE IN BLACK TIGER SHRIMP (PENAEUS-MONODON)

The leaves of Clinacanthus nutans Lindua, a well-known Thai traditiona l medicine against viral disease in human being, were used to extract antiviral substances by ethanol using soxhlet apparatus. The extract w as tested for its activity against yellow-head rhabdovirus (YRV) in bl ack tiger shrimp (Penaeus monodon). Virucidal effect was investigated by observation of mortality of the shrimp injected with the extract-tr eated virus. The results showed that extract of C. nutans inhibited YR V in vitro with the minimum concentration of 1 mu g/ml. Protective eff icacy of the extract on YRV infection in shrimp was tested by oral adm inistration of the extract mixed pellet. As the result, the protective efficacies obtained were 44.6, 57.4 and 4.2% in the shrimp groups fed the extract at 0.1, 1 and 10 g/kg pellet, respectively, indicating th at the C. nutans extract mixed with pellet at 1 g/kg could most effect ively control YRV infection in shrimp.