Efficacy of a pharmaceutical preparation based on glycyrrhizic acid in a challenge study of white spot syndrome in white shrimp (Litopenaeus vannamei)

There is a lack of preventive and therapeutic drug-based treatments for the shrimp viral disease known as white spot syndrome (WSSV). Thus a challenge study inducing WSSV in juvenile white shrimp (Litopenaeus vannamei) was established, setting 4 groups: challenged — not treated and unchallenged, untreated control groups and two experimental ones (E1 and E2) both treated with diammonium glycyrrhizic acid, extracted from licorice with added vitamins and oligoelements, and as in-feed medication. Group E1 received diammonium glycyrrhizic acid included in their daily feed, starting 17 days before challenge with WSSV and maintaining the treatment for further 5 days after the end of the trial, which was set on day 18. Group E2 received this medication as group E1 throughout the trial, but starting 1 day before the challenge with WSSV. The group with highest surviving median values was E1, amounting two times the survival median in comparison with the control groups (P = 0.007). Also a statistical difference was found in terms of survival means in favor of group E1 as compared to group E2. Macroscopic and histopathological findings revealed lesions compatible with WSSV and similar mortality in the challenged untreated group. These findings were highly reduced or inexistent in mortality analyzed from groups E1 as well as in the unchallenged — untreated control group and greatly reduced in group E2. Considering the apparent high efficacy observed and that glycyrrhizic acid and mineral and vitamin components added as treatment, and taking as an advantage that this preparation has been regarded as nutraceuticals, it is here proposed that large scale trials should be conducted to evaluate the effects here observed in commercial and larger scale shrimp farms.