Garlic (Allium sativum) has several bioactive compounds that provides various biological properties such as growth promotion and antimicrobial properties which can increase fish resistance to diseases. Pangasianodon hypophthalmus is a predominant finfish which originated from Mekong Delta region, Vietnam and has been cultured widely in Malaysia. The common pathogenic bacteria which can infect this species is Edwardsiella ictaluri.
The objective of this study is to investigate the prophylactic effect of garlic juice extract against Edwardsiella ictaluri infection in Pangasianodon hypophthalmus at control environment. Garlic juice extract was obtained by grinding with juicer and considered as 100% stock solution. Medicated pellet was prepared by spraying 80% concentration of garlic juice extract onto the pellet and allowed to air dried before use. Variable used in this experiment is the treatment duration, which are 5 days, 10 days, 15 days, positive control (fed with commercial pellet and challenged with bacteria), and negative control (fed with commercial pellet but not challenged with bacteria). The concentration of Edwardsiella ictaluri used to challenge the fish was 108 cfu/ml. Ten fish were used in each group with duplicates. The feeding ratio was 3% from total body weight. Fish were fed with 80% concentration of garlic juice extract before challenged with Edwardsiella ictaluri through intraperitoneal injection method. Clinical signs and mortalities were observed and recorded for 30 days of experiment. The results showed that no mortality observed in tank treated with garlic (5 days,10 days,15 days) throughout 30 days of experiment with mild clinical signs such as pale body, hemorrhagic fin, and hemorrhagic tail. For positive control, 5 mortalities were recorded with several severe clinical signs such as pale body, hemorrhagic tail, hemorrhagic fin, erratic swimming, and bilateral exophthalmia (Figure 1). As for statistical analysis, ANOVA test showed that average mortality of Pangasianodon hypophthalmus was significantly difference (P <0.05) between 5 different groups of treatment. In conclusion, garlic juice is very effective to prevent Pangasianodon hypophthalmus against Edwardsiella ictaluri infection in the control environment.