Aims: Vibrio harveyi causes vibriosis to Asian seabass (Lates calcarifer). The disease spreads rapidly among fish stocked in the same cage. It causes high mortality especially in weak and small sized fish stocked at high density in poorly managed net cage. Study to determine the virulence levels of the bacterial pathogen in various aquaculture animals is a key to prevent vibriosis in marine aquaculture. Methodology and Result: Isolation of bacteria from diseased Asian seabass was done using tryptic soy agar (TSA) and thiosulphate citrate bile sucrose agar (TCBS) plates. Virulence of two strains of Vibrio harveyi (VHJR4 and VHJR7) was tested against clinically healthy aquaculture animals. The analysis revealed that the two bacterial strains differ in pathogenicity. The V. harveyi strain VHJR7 was virulent to Asian seabass at 1.40 x 10 4 c.f.u. g -1 , humpback grouper (Cromileptis altivelis) at LD50 8.33 x 10 3 c.f.u. g -1 and black tiger shrimp (Penaeus monodon) at LD50 3.26 x 10 4 c.f.u. g -1 , respectively. The V. harveyi strain VHJR4 was not virulent to Asian seabass and humpback grouper but it caused mortality to black tiger shrimp at LD50 1.32 x 10 6 c.f.u. g -1. Phenotypically, the two strains shared most of the biochemical features except that the V. harveyi strain VHJR7 was a urease positive and grew at 8.5 % NaCl, and at 10 °C. The percentage similarity of nucleotide sequences of 16S rDNA in V. harveyi VHJR4 and V. harveyi VHJR7 was higher (99 %) but reduced at 95 % in hemolysin gene. Conclusion, significance and impact of study: Pathogenic strain of V. harveyi causes mortality and affects aquaculture production of Asian seabass. Hence, vaccine development against the bacterial pathogen is urgently needed for sustainability of Asian seabass aquaculture in Malaysia.
This chapter examines the role of poultry breeding technology as it relates to the skeletal system. It discusses how selection, for increased productivity, has affected skeletal integrity and mineralization in layers. It also discusses how it affects bone, tendon and ligament growth, and strength and the development of musculoskeletal disease in meat-type poultry.
The grow out of Asian seabass Lates calcarifer in marine net-cages is a popular aquaculture activity in Malaysia. Production of this species is greatly affected by the occurrence of vibriosis, which causes heavy mortality. Generally, young fish are more susceptible; they exhibit anorexia and skin darkening, followed by heavy mortality. The acutely affected older fish may also exhibit bloody lesions around the anus and the base of the fins. Twenty-one bacterial isolates obtained from internal organs (kidney, heart, spleen and liver) of the affected specimens were subjected to phenotypic characterization, testing for antibiotic susceptibility, and 16S ribosomal DNA sequencing. The sequencing result showed that all of the bacterial isolates belonged to Vibrio harveyi. The phenotypic characterization, however, identified 4 of the bacterial isolates as V. harveyi, 16 as V. parahaemolyticus, and 1 as V. alginolyticus. These findings suggest that biochemical features alone cannot be reliably used to identify bacterial pathogens, including V. harveyi, in aquaculture. Antibiotic susceptibility assays showed that some antibiotics, including oxytetracycline, nitrofurantoin, furazolidone, streptomycin, sulfamethoxazole, chloramphenicol, nalidixic acid, and oxolinic acid were effective against V. harveyi. Considering the side effects of these antibiotics, however, their use is not recommended in the aquaculture of Asian seabass.
The region of northern Borneo is home to the current state of Sabah, Malaysia. It is located closest to the southern Philippine islands and may have served as a viaduct for ancient human migration onto or off of Borneo Island. In this study, five indigenous ethnic groups from Sabah were subjected to genome-wide SNP genotyping. These individuals represent the "North Borneo"-speaking group of the great Austronesian family. They have traditionally resided in the inland region of Sabah. The dataset was merged with public datasets, and the genetic relatedness of these groups to neighboring populations from the islands of Southeast Asia, mainland Southeast Asia and southern China was inferred. Genetic structure analysis revealed that these groups formed a genetic cluster that was independent of the clusters of neighboring populations. Additionally, these groups exhibited near-absolute proportions of a genetic component that is also common among Austronesians from Taiwan and the Philippines. They showed no genetic admixture with Austro-Melanesian populations. Furthermore, phylogenetic analysis showed that they are closely related to non-Austro-Melansian Filipinos as well as to Taiwan natives but are distantly related to populations from mainland Southeast Asia. Relatively lower heterozygosity and higher pairwise genetic differentiation index (F ) values than those of nearby populations indicate that these groups might have experienced genetic drift in the past, resulting in their differentiation from other Austronesians. Subsequent formal testing suggested that these populations have received no gene flow from neighboring populations. Taken together, these results imply that the indigenous ethnic groups of northern Borneo shared a common ancestor with Taiwan natives and non-Austro-Melanesian Filipinos and then isolated themselves on the inland of Sabah. This isolation presumably led to no admixture with other populations, and these individuals therefore underwent strong genetic differentiation. This report contributes to addressing the paucity of genetic data on representatives from this strategic region of ancient human migration event(s).
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