Effect of dietary beta-1,3-glucan on resistance to white spot syndrome virus (WSSV) in postlarval and juvenile Penaeus monodon

This study evaluated the effectiveness of dietary incorporation of beta-1,3 -glucan from Schizophyllum commune in enhancing the resistance of postlarva l (PL15) or juvenile (5.5 +/- 0.5 g) Penaeus monodon to white spot syndrome virus (WSSV). The shrimp were fed experimental diets with (2 g kg(-1) diet ) or without beta-1,3-glucan for 15 d (postlarvae) or 10 or 20 d (juveniles ). Following these dietary treatments, the postlarvae were challenged by im mersion and the juveniles by injection using WSSV solution. After challenge with WSSV, initial mortality was significantly (p < 0.005) lower in all th e glucan-fed groups than in the respective non-glucan control groups. In th e juvenile groups, glucan supplementation for 20 d rather than 10 d signifi cantly (p < 0.005) enhanced survival. After the WSSV challenge. none of the control diet postlarvae or juveniles survived beyond 4 d and none of the 1 0 d glucan-fed juveniles survived beyond 6 d. By contrast, some of the gluc an-treated postlarvae (12.2 %) and some of the 20 d glucan-treated juvenile s (20%) were still alive at Day 6. These surviving individuals were reared onwards up to 120 d post-challenge, at which time overall survivals were 5. 5 % (postlarvae) and 13.3% (juveniles) and body weights were 25 to 30 g (po stlarvae) and 30 to 40 g (juveniles). Half of the surviving postlarvae and 58% of the surviving juveniles were 2-step WSSV polymerase chain reaction ( PCR) negative 6 d after challenge. FLU the surviving shrimp were 2-step WSS V PCR negative 120 d after challenge.