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 (T-C, negative control), WSSV-infected shrimp fed with commercial pelleted feed (T-1, positive control), WSSV-infected shrimp fed with commercial pelleted feed with 0.1% TEM (T-2), WSSV-infected shrimp fed with commercial pelleted feed with 0.5% TEM (T-3), and WSSV-infected shrimp fed with commercial pelleted feed with 1% TEM (T-4). At 72h post infection, phenoloxidase activity of shrimps treated with 1% TEM did not show significant differences with T-C values but it was significantly higher than that of the other treatments (T-1, T-2, and T-3). Moreover, shrimps treated with T-4 presented absence of clinical signs of WSSV infection and their survival rate was significantly higher than that of T-1, T-2, and T-3 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.