Effect of dietary β-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 β-1,3-glucan from Schizophyllum commune in enhancing the resistance of postlarval (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 β-1,3-glucan for 15 d (postlarvae) or 10 or 20 d (juveniles). Following these dietary treatments, the postlarvae were challenged by immersion and the juveniles by injection using WSSV solution. After challenge with WSSV, initial mortality was significantly (p < 0.005) lower in all the glucan-fed groups than in the respective non-glucan control groups. In the juvenile groups, glucan supplementation for 20 d rather than 10 d significantly (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 10 d glucan-fed juveniles survived beyond 6 d. By contrast, some of the glucan-treated postlarvae (12.2%) and some of the 20 d glucan-treated juveniles (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 (postlarvae) 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. All the surviving shrimp were 2-step WSSV PCR negative 120 d after challenge.