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Abstract:
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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. |