Cynodon dactylon as potential anti-white spot syndrome virus agent in cultured shrimp Penaeus vannamei

Abstract

White spot syndrome virus (WSSV) has been listed as the most contagious pathogen causing severe mortality in farmed shrimp and substantial economic losses. A bioassay experiment was conducted to determine Cynodon dactylon extract's efficacy as an anti-WSSV treatment at the laboratory scale and cage level. A pond trial was performed to optimize and investigate the effects of C. dactylon-enriched feed. The trial's first step was performed using feed coated with 2% and 3% of ethanol-extracted C. dactylon. The shrimp were challenged with the virus on day 15 of feeding with the treatment feed and monitored. A total of 100% survival of shrimp was obtained in both treatment groups. The (Rajeev anti-viral) RAV-s C group had the best protection (100% survival) of three groups treated with crude extracts, including RAV-s A (10%), RAV-s B (15%) and RAV-s C (20%) mixed feed. Similar results were obtained in the cage level trial with crude extracts, where the RAV-s C group had the highest survival (100%) followed by RAV-s A (68%) and RAV-s B (85.05%). Pond trials were conducted in commercial ponds. A total of 20 units of shrimp ponds of the same size (5,000 m2) and location were selected for the trial. The treatment ponds' productivity was higher (12.7 ton/ha) than that of the control ponds (11.79 ton/ha). WSSV cases were not recorded in the control and treatment ponds. This study showed that C. dactylon extract has anti-WSSV properties and has no negative impact on shrimp growth.