Elucidation of inactivated microbial with Sargassum sp. as immunostimulants against Vibrio parahaemolyticus inducing acute hepatopancreatic necrosis disease in Penaeus vannamei (Boone, 1931)
Acute hepatopancreatic necrosis disease (AHPND) is an emerging disease in shrimp aquaculture industry caused by Vibrio parahaemolyticus. It imposes a serious threat to shrimp production through mass mortality of post-larval shrimp resulting USD 1 billion loss to the shrimp industry worldwide incl...
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| Format: | Thesis |
| Language: | English |
| Published: |
2023
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/119491/ http://psasir.upm.edu.my/id/eprint/119491/1/119491.pdf |
| Summary: | Acute hepatopancreatic necrosis disease (AHPND) is an emerging disease in
shrimp aquaculture industry caused by Vibrio parahaemolyticus. It imposes a
serious threat to shrimp production through mass mortality of post-larval shrimp
resulting USD 1 billion loss to the shrimp industry worldwide including Malaysia.
Therefore, this study aimed to characterize V. parahaemolyticus strains causing
AHPND in shrimp from a local shrimp farm in Malaysia, to develop an inactivated
microbial immunostimulant from V. parahaemolyticus for protection against
AHPND in shrimp, to conduct immunization trials of the inactivated microbial in
combination with Sargassum sp. as immunostimulants in shrimp infected with
AHPND, and to study the effect of immunization in shrimp immune system at the
transcriptional level. In this study, isolates associated with AHPND outbreak had
been isolated previously from a shrimp farm in Terengganu, Malaysia, and were
further characterized. Based on the phenotypic characterization and phylogenetic
analysis, strain C2A and C4B were identified as V. parahaemolyticus, meanwhile,
strain C1B, C2B, C4A, and C5 were V. harveyi. This study suggested that, in
Malaysia, both V. parahaemolyticus and V. harveyi could be the pathogen that
caused AHPND outbreak in a local shrimp farm. The most virulent AHPND positive
isolate in this experiment is V. parahaemolyticus C4B. The draft genome sequence
of C4B were also compared with V. parahaemolyticus P24 which is a non-causing
AHPND strain. The genome assembly metrics for revealed features transposons
and insertion sequences, and bacteriophages are more abundant in the V.
parahaemolyticus VPAHPND C4B genome compared to V. parahaemolyticus VPNONAHPND,
P24, reflecting the organism’s genome plasticity and pathogenic features.
Despite these variations, all genomes exhibited greater than 98.0% average
nucleotide identity (ANI), indicating they belong to the same species. Notably, V.
parahaemolyticus AHPND strains NCKU_TV_5HP and NCKU_CV_CHN showed
ANI indices of 98.46% and 98.43%, respectively, when compared to strain C4B.
Next is to develop an inactivated bacterial with Sargassum sp. as
immunostimulants as potential protection against the AHPND in shrimp. The
treatment group for this study was as follows, group 1: commercial feed, group 2:
immunostimulant 1x103 CFU kg/feed, group 3: immunostimulant 1x105 CFU
kg/feed, group 4: immunostimulant 1x107 CFU kg/feed, group 5: immunostimulant
1x103 CFU kg/feed + 2% Sargassum sp., group 6: immunostimulant 1x105 CFU
kg/feed + 2% Sargassum sp., group 7: immunostimulant 1x107 CFU kg/feed + 2%
Sargassum sp., and group 8: 2% Sargassum sp. After four weeks of the treatment
period, immunostimulants with Sargassum sp. treatment groups (groups 5, 6, and
7) showed the highest percentage (>60%) of shrimp survival compared to
treatment groups without Sargassum sp. Meanwhile, group 6 showed the highest
shrimp survival after four weeks of immunization. After the challenge study, group
6 also showed the highest survival percentage, 64% compare to other treatment
groups indicating that the immunostimulant of 1×105 CFU with Sargassum sp. was
the best treatment in this study to increase disease against AHPND and to prevent
mortalities in shrimp. The effect of the immunization using the immunostimulants
had been further elucidated at the transcriptional level to find out its immune
response on immunized shrimp’s gene expression compared to control group.
Based on the differentially expressed genes (DEGs) detected in the KEGG
pathway database, several notable changes in the immune-related genes such as
antimicrobial peptides (anti-lipopolysaccharide factor, penaeidin, crustin),
prophenoloxidase (proPO) gene cascade and upregulation of antioxidant gene
expressions were identified following the immunization. This study's findings
provide recent data on AHPND-associated isolates such as V. parahaemoluticus
and V. harveyi, insights into the genome and its virulence, and information on the
use of inactivated microbial with Sargassum sp. as immunostimulants as a means
of disease protection coherent for sustainable prawn global production. |
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