First detection of white spot syndrome virus (WSSV) in wild mud crab Scylla spp. (de Haan, 1883) from Setiu Wetlands, Malaysia

In this study, tissue samples from 90 wild mud crabs (Scylla spp. including S. olivacea, S. Tranquebarica, and S. paramamosain) were collected during pre-monsoon, monsoon, and post-monsoon in the Setiu Wetlands, Terengganu, Malaysia. The tissue samples were screened for the presence of white spot syndrome virus (WSSV) by PCR. This study was conducted to detect the presence or absence of WSSV in wild Scylla spp. from the Setiu Wetlands at different times of sampling. WSSV DNA was detected in 36% of the mud crabs. The DNA sequence of a 941 bp genome region amplified from a crab by PCR was identified to be most similar (99% nucleotide sequence, 98% amino acid sequence) to a WSSV strain detected in Mexico (KU216744.1) and Taiwan WSSV 419 strain (AY850066.1). The data indicated that mud crabs in the Setiu Wetlands might act as a WSSV reservoir of risk to shrimp aquaculture. Our findings are the first detection of WSSV from wild mud crabs, Scylla spp. in the Setiu Wetlands, Terengganu, Malaysia

RNA interference of Hsp70 in Artemia franciscana nauplii and its effect on morphology, growth, survival and immune response

Brine shrimp Artemia franciscana release either encysted embryos via oviparous reproduction or motile nauplii via ovoviviparous reproduction. Artemia cysts contain an abundant amount of ArHsp21, ArHsp22, artemin, and p26, small heat shock proteins which regulate diapause and stress tolerance of this branchiopod crustacean. However, not much is known of the role of molecular chaperone, Hsp70 in this animal. In this study, the immunostimulatory role of Hsp70 in A. franciscana was investigated, work which included examining the function of this protein in embryo development, growth, survival and stress tolerance. Knockdown of Hsp70 was successfully performed by RNA interference (RNAi), with specific Hsp70 dsRNA construct delivered to female broods by microinjection to knockdown the protein in nauplii. The loss of Hsp70 neither affected the growth nor morphology as Artemia nauplii hatched normally and thereafter grew to adult within 28 days, observations similar to the control animals, the latter injected with GFP dsRNA. The survival of nauplii lacking Hsp70 appeared lower upon 28 days culture but the differences were insignificant when comparisons were made with the controls (P > .05). On other aspect, knockdown of Hsp70 reduced approximately 31% survival upon Vibrio campbellii challenge, indicating that Hsp70 assisted in the tolerance of Artemia nauplii during pathogen infection, perhaps through immune stimulation. Initial findings revealed that Hsp70 knockdown did not affect the expression of prophenoloxidase (proPO), a crucial immune protein of the shrimp innate immunity. By examining the morphology, growth, viability and molecular changes upon Hsp70 elimination, this study contributes to our understanding of the important roles of Hsp70 in A. franciscana, an important live food species used in aquaculture

Pandanus tectorius fruit extract promotes Hsp70 accumulation, immune-related genes expression and Vibrio parahaemolyticus tolerance in the white-leg shrimp Penaeus vannamei

Plants and herbal extracts are indispensable for controlling the spread of disease-causing bacteria, including those that infect aquatic organisms used in aquaculture. The use of plant or herbal extract is expected to be safe for aquatic animals and less harmful to the environment, as opposed to conventional therapeutic alternatives such as antibiotics that promote the occurrence of potential antibiotic-resistant bacteria when used improperly. The efficacy of Pandanus tectorius fruit extract in the regulation of Hsp70 expression, pro-phenoloxidase (ProPO), peroxinectin, penaeidin, crustin and transglutaminase, all immune peptides essential for Vibrio tolerance in white leg shrimp, Penaeus vannamei, was investigated in this study, which included the determination of the safety levels of the extract. Tolerance of shrimp against Vibrio parahaemolyticus, a pathogenic bacteria that causes Acute Hepatopancreas Necrosis Disease (AHPND), was assessed on the basis of median lethal dose challenge survival (LD50=106cells/ml). Mortality was not observed 24h after exposure of 0.5-6g/L of the fruit extract, indicating that P. tectorius was not toxic to shrimp at these concentrations. A 24-h incubation of 2-6g/L of the fruit extract increased shrimp tolerance to V. parahaemolyticus, with survival doubled when the maximum dose tested in this study was used. Concomitant with a rise in survival was the increase in immune-related proteins, with Hsp70, ProPO, peroxinectin, penaeidin, crustin and transglutaminase increased 10, 11, 11, 0.4, 8 and 13-fold respectively. Histological examination of the hepatopancreas and muscle tissues of Vibrio-infected shrimp primed with P. tectorius extract revealed reduced signs of histopathological degeneration, possibly due to the accumulation of Hsp70, a molecular chaperone crucial to cellular protein folding, tissue repair and immune response of living organisms, including Penaeid shrimp