Application of Spirulina platensis for prevention of white spot syndrome virus in post larvae and juvenile black tiger shrimp (Penaeus monodon)

In this study, the extract of Spirulina platensis were examined in vitro to inhibit white spot syndrome virus (WSSV) and application of dry S. platensis in diet for prevention of white spot syndrome (WSS) in post larvae and juvenile black tiger shrimp (Penaeus monodon). The results showed that the lowest concentration of the extract for inhibiting WSSV was 0.01 mg/ml, while the optimum concentration was found to be 0.1 mg/ ml in which the mortality rate of the shrimp was 4 percents and infection was not detected from survivalshrimp by the immunohistochemistry method.Furthermore, The results showed that the survival rate of the post larvae fed on steamed egg containing dry S. platensis 5 g/kg of diet was higher than that of the control (p<0.05) when challenged with WSSV and no WSSV infected shrimp examine by polymerase chain reaction (PCR) assay. In the case of juvenile shrimp, the survival rate of shrimp fed pellets containing dry S. platensis 10 g/kg of diet was higher than that of the control group (p<0.05) after challenging with WSSV. Moreover percent of WSSV infection in the survival shrimp using the immunohistochemistry method was lower than that of the control group

Efficacy of Thai Traditional Herb Extracts against Fish and Shrimp Pathogenic Bacteria

Sixteen species of Thai traditional herbs were selected for this study. They were Andrographis paniculata, Cassia alata, Clinacanthus nutans, Eclipta alba, Momordica charantia, Phyllanthus acidus, P. amarus, P. debilis, P. pulcher, P. reticulatus, P. urinaria, Psidium guajava, Tinospora cordifolia, T. crispa and white and red strains or Ocimum sanctum. Using an agar plate dilution method, they were tested for antibacterial activity against the pathogenic bacteria: Aeomonas hydrophila, a Streptococcus species and 10 strains of Vibrio. Eleven of the tested herbs showed antibacterial activity. Among them, P. guajava and M. charantia displayed the highest activity against Vibrio harveyi and V. parahaemolyticus. The minimal inhibitory concentration (MIC) of P. guajava against the tested bacteria was found to be 0.625mg/ml, while the MIC of M. charantia was 1.25 mg/ml

Protective Efficacy of Clinacanthus nutans on Yellow-head Disease in Black Tiger Shrimp (Penaeus monodon)

The leaves of Clinacanthus nutans Lindua, a well-known Thai traditional medicine against viral disease in human being, were used to extract antiviral substances by ethanol using soxhlet apparatus. The extract was tested for its activity against yellow-head rhabdovirus (YRV) in black tiger shrimp (Penaeus monodon). Virucidal effect was investigated by observation of mortality of the shrimp injected with the extract-treated virus. The results showed that extract of C. nutans inhibited YRV in vitro with the minimum concentration of 1μg/ml. Protective efficacy of the extract on YRV infection in shrimp was tested by oral administration of the extract mixed pellet. As the result, the protective efficacies obtained were 44.6, 57.4 and 4.2% in the shrimp groups fed the extract at 0.1, 1 and 10g/kg pellet, respectively, indicating that the C. nutans extract mixed with pellet at 1 g/kg could most effectively control YRV infection in shrimp

Efficacy of Guava (Psidium Guajava) Extract Against Some Fish and Shrimp Pathogenic Agents

Guava (Psidium guajava) extract was tested for anti viral activity against the fish pathogenic viruses, infectious haematopoietic necrosis virus (IHNV), infectious pancreatic necrosis virus (IPNV), and Oncorhynchus masou virus (OMV) using plaque reduction in CHSE-214 cell lines. Anti viral tests against the shrimp pathogenic virus, yellow-head virus (YHV), was carried out using the injection method. The efficacy of guava extract was also determined using MIC of the extract against 24 strains of pathogenic bacteria including; Vibrio harveyi (9 strains), V. splendidus (7 strains), V. parahaemolyticus (2 strains) and 1 strain of each V. mimicus, V. vulnificus, V. fluvialis, V. chorelae, V. alginolyticus and Aeromonas hydrophila. A toxicity test of the extract was performed with CHSE-214 cell lines and post larvae 15 of black tiger shrimp (Penaeus monodon). The efficacy of guava extract for the prevention of viral disease and bacterial disease in aquatic animals was estimated using YHV infection in black tiger shrimp and A. hydrophila infection in catfish, respectively. The extract of guava demonstrated anti viral activity against IHNV, OMV and YHV but was not effective for IPNV. Furthermore, the MIC of the extract ranged from 625 - 5,000 μg/ml against all pathogenic bacterial strains tested. The 50% cytotoxicity of the extract to CHSE-214 was 1,923 μg/ml while the LD50 of the extract to black tiger shrimp post larvae was 2,968 ± 3.8 μg/ml. These results show that guava extract has low toxicity to salmon cell lines and black tiger shrimp. Moreover, the extract is effective for prevention of bacterial infection in catfish (Clarias macrocephalus) while not suitable for prevention of yellow-head virus infection in black tiger shrimp. From these results, guava can be recommended for treatment of bacterial disease in fish. The route of administration and effective dose should be determined before their efficacy can be tested in field trials.Third Symposium on Diseases in Asian Aquaculture. 1996. Bangkok, Thailand