Effect of microencapsulated thyme essential oil on white spot virus-infected Litopenaeus vannamei

The present work was performed to investigate if feeding Litopenaeus vannamei with microencapsulated thyme essential oil (TEM, 1.05 g thyme essential oil per 100-g powder) adsorbed on commercial pellet feed was able to protect shrimps against white spot syndrome virus (WSSV) disease. Five treatments were tested: uninfected shrimp fed with commercial pelleted feed (TC, negative control), WSSV-infected shrimp fed with commercial pelleted feed (T1, positive control), WSSV-infected shrimp fed with commercial pelleted feed with 0.1% TEM (T2), WSSV-infected shrimp fed with commercial pelleted feed with 0.5% TEM (T3), and WSSV-infected shrimp fed with commercial pelleted feed with 1% TEM (T4). At 72 h post infection, phenoloxidase activity of shrimps treated with 1% TEM did not show significant differences with TC values but it was significantly higher than that of the other treatments (T1, T2, and T3). Moreover, shrimps treated with T4 presented absence of clinical signs of WSSV infection and their survival rate was significantly higher than that of T1, T2, and T3 treatments. Therefore, 1% TEM seemed to protect shrimps against WSSV symptoms. Using microencapsulated thyme essential oil may help to fight against WSSV in shrimp farms.