Mangrove plant Ceriops tagal as a potential source of anti White Spot Syndrome Virus preparations for Penaeus monodon

White spot syndrome virus (WSSV) is the deadliest virus among crustaceans ever discovered having several unique and novel features. Recent developments in genomics and proteomics could elucidate the molecular process involved in the WSSV infection and the host pathogen interaction to some extent. Until now no fool proof treatment or prophylactic measure has been made available to control WSSV out breaks in culture system. Even though there are technologies like application of immunostimulants, vaccines, RNAi and several antiviral natural products none of them has been taken to the level of clinical trials. However, there are several management options such as application of bioremediation technologies to maintain the required environmental quality, maintenance of zero water exchange systems coupled with application of probiotics and vaccines which on adoption shall pave way for successful crops amidst the rapid spread of the virus. In this context the present work was undertaken to develop a drug from mangrove plants for protecting shrimp from WSSV.Mangroves belong to those ecosystems that are presently under the threat of destruction, diversion and blatant attack in the name of so called ‘developmental activities’. Mangrove plants have unique ecological features as it serves as an ecotone between marine and terrestrial ecosystem and hence possess diversity of metabolites with diverse activities. This prompted them being used as remedial measures for several ailments for ages. Among the mangrove plants Ceriops tagal, belonging to the family Rhizophororaceae was in attention for many years for isolating new metabolites such as triterpenes, phenolic compounds, etc. Even though there were attempts to study various plant extracts to develop anti-viral preparations their activity against WSSV was not investigated as yet.

Anti–white spot syndrome virus activity of Ceriops tagal aqueous extract in giant tiger shrimp Penaeus monodon

White spot syndrome virus (WSSV), the most contagious pathogen of cultured shrimp, causes mass mortality, leading to huge economic loss to the shrimp industry. The lack of effective therapeutic or prophylactic measures has aggravated the situation, necessitating the development of antiviral agents. With this objective, the antiviral activity in the aqueous extract of a mangrove plant Ceriops tagal in Penaeus monodon was evaluated. The Ceriops tagal aqueous extract (CTAE) was non-toxic to shrimps at 50 mg/ml when injected intramuscularly at a dosage of 10 lL/animal (0.5 mg/animal) and showed a protective effect against WSSV at 30 mg/ml when mixed with WSSV suspension at a 1:1 ratio. When the extract was administered along with the diet and the animals were challenged orally, there was a dose-dependent increase in survival, culminating in 100 % survival at a concentration of 500 mg/kg body weight/day. Neither hypertrophied nuclei nor the viral envelope protein VP28 could be demonstrated in surviving shrimps using histology and indirect immunofluorescence histochemistry (IIFH), respectively. To elucidate the mode of action, the temporal expression of WSSV genes and shrimp immune genes, including antimicrobial peptides, was attempted. None of the viral genes were found to be expressed in shrimps that were fed with the extract and challenged or in those that were administered CTAE-exposed WSSV. The overall results suggest that the aqueous extract from C. tagal can protect P. monodon from white spot syndrome virus infection.