Transmission and pathology of Streptococcus inane in monosex Nile tilapia (Oreochromis niloticus) in aquaculture of Bangladesh

Streptococcus iniae is a major fish pathogen, recently emergent outbreaks were recorded in commercially cultured monosex Nile tilapia (Oreochromis niloticus) result in significant losses termed “streptococcosis”-causes unusual appearances with multi-focal pin-point haemorrhages, abscesses, necrosis and ascites in skin, fin, muscle, liver, spleen, kidney, blood, interstitial fluid specially in central nervous system and brain. This disease was more prevalent (>26%) at summer when the water temperature was approximately >25oC, percentage of mortality was higher >41% during the overcrowding and improper water chemistry. Raised levels of glucose and ammonium in blood serum causes reduced number of free blood cells released into the haemolymph to stomach and gut, result in refrain from eating in diseased tilapia. Stocking density (200 fish/decimal; class IV) had significant effect (P<0.01) on the total production (5,000 to 5,500 kg/ha). S. iniae in the circulating blood cells, extra-tubular haemal spaces containing blood vessels, fixed phagocytes in the hepatopancreas (gastrointestinal tract), bacteria-like particles in the brain tissue, vacuum and necrosis in hepatocytes revealed with histopathology. In vitro study revealed that cohabitation of dead or infected fish with healthy fish resulted infection (horizontal transmission mechanism) to the healthy fish

Farming of giant freshwater prawn (Macrobrachium rosenbergii) in Bagerhat, Bangladesh

The study was carried out to know the present status of Macrobrachium rosenbergii culture in Bagerhat district, Bangladesh from March 2012 to January 2013. Education levels  of farmers were found as illiterate (12.3%), primary (36.19%), secondary (20%), SSC (13.33%), HSC (12.38%) and graduate (5.71%). M. rosenbergii culture was the primary and secondary occupation of 80% and 20% farmers respectively. Average stocking density and production in extensive, improved extensive and semi-intensive culture were 9609, 11502 and 22847 per ha and 193, 284 and 488 kg/ha/year respectively; rearing period ranges from 6-10 months and survival rate varied from 55 to 60%. In improved extensive and semi-intensive culture 82.86% and 71.43% farmers applied farm-made feed instead of company feeds respectively and 11.43% and 37.14% farmers used both feeds. 91.43%, 80% and 68.57% respondents responded on normal to high mortality in extensive, improved extensive and semi-intensive culture respectively. Lack of finance and appropriate technology, scarcity of quality PL, diseases and inadequate extension work were major problems of prawn culture

Socio-economic status of fishermen of the Marjat Baor at Kaligonj in Jhenidah district, Bangladesh

This study was carried out to assess the socio-economic status of fishermen of the Marjat Baor at Kaligonj of Jhenidah district. Fifty fishermen from 50 families were interviewed. Results revealed that 94% respondents were married and age varied between 30 and 45 years. Almost all the fishermen were Hindus (96%). Most of the people of the community were illiterate (60%) and among all of the school going children (58%) were boys and (42%) were girls. Above fifty percent people lived in nuclear family. 40% people lived in earthen house, constructed by grass leaves and mud. Only a few (18%) of them were found to be use electricity. Primary occupation of 60% respondents was fishing and few were also involved in agriculture. They were often found to suffer from various diseases due to lack of pure drinking water. Majority of them got fever and receive treatment from quack. Only twelve percent (12%) women were engaged in making nets for fishing. Annual household income of maximum beneficiaries (44%) was below BDT 30,000 and above BDT 50,000 found in only 4% cases. In the present study, educational, organizational, and technical credit support were very crucial to develop their better socio-economic conditions

Impact of diseases on fish production of baors in Jessore, Bangladesh

The study was carried out to assess the impact of diseases on fish production in baors of Jessore district, Bangladesh from March 2012 to January 2013. Studied baors were selected randomly from each sub-district which covered 39.22% of total baors and 71.87% baor areas in Jessore district. All the surveyed baors were affected more or less by various diseases and in 80% baors noticeable production loss occurred almost every year. The main diseases were epizootic ulcerative syndrome (EUS), dropsy, gill rot and fin rot; out breaking time ranged from November to February each year. EUS was recorded in 85% baors whereas other diseases were found in various baors at various percentages: dropsy (75%), gill rot (45%) and fin rot (55%). Conferring to the number of affected fishes, 31.25% were affected by EUS, 37.5% by dropsy, 12.5% by gill rot and 18.75% by fin rot. In the year 2012, 0.513% loss of production has occurred that designated 0.7599 million BDT. Through successful work on disease control and management, production loss may be minimized

Transmission and pathology of Streptococcus inane in monosex Nile tilapia (Oreochromis niloticus) in aquaculture of Bangladesh

Streptococcus iniae is a major fish pathogen, recently emergent outbreaks were recorded in commercially cultured monosex Nile tilapia (Oreochromis niloticus) result in significant losses termed “streptococcosis”-causes unusual appearances with multi-focal pin-point haemorrhages, abscesses, necrosis and ascites in skin, fin, muscle, liver, spleen, kidney, blood, interstitial fluid specially in central nervous system and brain. This disease was more prevalent (>26%) at summer when the water temperature was approximately >25oC, percentage of mortality was higher >41% during the overcrowding and improper water chemistry. Raised levels of glucose and ammonium in blood serum causes reduced number of free blood cells released into the haemolymph to stomach and gut, result in refrain from eating in diseased tilapia. Stocking density (200 fish/decimal; class IV) had significant effect (P<0.01) on the total production (5,000 to 5,500 kg/ha). S. iniae in the circulating blood cells, extra-tubular haemal spaces containing blood vessels, fixed phagocytes in the hepatopancreas (gastrointestinal tract), bacteria-like particles in the brain tissue, vacuum and necrosis in hepatocytes revealed with histopathology. In vitro study revealed that cohabitation of dead or infected fish with healthy fish resulted infection (horizontal transmission mechanism) to the healthy fish

Genes expression in Penaeus monodon of Bangladesh; challenged with AHPND-causing Vibrio parahaemolyticus

Vibrio parahaemolyticus, the causative agent of Acute hepatopancreatic necrosis disease (AHPND), was discovered in 2013 as a unique isolate that produces toxins and kills penaeid shrimps in devasting nature in Bangladesh and causes severe economic losses. This research aimed to understand the expressions of immune genes in different stages of the host species, Penaeus monodon, against virulence and toxin genes upon being challenged with V. parahaemolyticus. Healthy post-larvae (PL) samples were collected from southwestern of Bangladesh from July 2021 to August 2022. The tryptic soy agar with 1.5% sodium chloride (NaCl) was used to inoculate the cells of V. parahaemolyticus, and the tryptic soy broth (TSB) with 1.5% NaCl was used to transfer the colonies. The spectrophotometry measured bacteria density. PCR, qPCR, SDS-PAGE, and Western blot measured gene expression and survivability after the immersion challenge. The 1 × 105CFU/mL of V. parahaemolyticus was used for 144 h.p.i (hours post-infection) challenge to six stages of post-larvae (PL) of P. monodon (PL20, PL25, PL30, PL35, PL40, and PL45), PL30 and PL35 showed 100% mortality by day 72 (h.p.i.) after exposure that indicated most vulnerable to V. parahaemolyticus. The expression of immune and toxic genes was confirmed by qPCR. The immune genes toll-like receptors (TLR), prophenoloxidase (ProPO), lysozyme (lyso), and penaeidin (PEN) of PL20 and PL25 of P. monodon were expressed robustly up-trends. PL30 and PL35 showed the lowest gene expression at the end of 72 (h.p.i.). At the end of the 144 (h.p.i.) exposure, the immune genes TLR, ProPO, lyso, and PEN expressed highest in PL45 than other post-larvae stages of P. monodon. The toxic genes (pirA, ToxR, ToxA, ToxB, tlh, tdh, and trh) in PL30 and PL35 of P. monodon after exposure of V. parahaemolyticus were expressed highest at the end of the 72 (h.p.i.). The lowest toxic genes expressions were revealed in PL20 and PL45 at the end of the 144 (h.p.i.). The SDS-PAGE analysis of proteins from the bacterium revealed identical protein profiles with toxic genes, and those toxins were further confirmed by Western blot. The 20 kDa, 78 kDa (ToxR), 20 kDa, 25 kDa (ToxA), 25 kDa (ToxB), 20 kDa, 27 kDa, 75 kDa (tdh), and 20 kDa, 27 kDa, 75 kDa, and 78 kDa (trh) proteins were strong responses in Western blot, indicating the crucial involvement of these immune-related genes in the defense and recovery of the first-line defense mechanisms during V. parahaemolyticus infection to shrimp. The all-toxic genes showed a unique homology and those derived from the common ancestor compared with V. parahaemolyticus (NCBI accession no. AP014859.1). All clades were derived with different traits with very low genetic distance, where the overall mean distance was 3.18 and showed a very uniform and homogenous pattern among the lineages. The V. parahaemolyticus infection process in different PL stages in P. monodon revealed novel insights into the immune responses. The responses may lead to the subsequent production of a DNA vaccine, enhancing shrimp health management to minimize the economic losses due to AHPND experiencing an outbreak of early mortality syndrome (EMS) toward sustainable production P. monodon (shrimp)

Diversity of bacterial communities in the Sundarbans mangrove, Bangladesh, with special focus on pathogens affecting aquatic organisms

The Sundarbans, located in Bangladesh, is the world's largest mangrove forest with a rich and diverse microbial community. The main objective of this study was to use 16S rRNA sequencing to identify the bacterial community in the Sundarban mangrove forest, particularly pathogenic bacteria to aquatic organisms. This study conducted in Bangladesh collected 225 samples of soil, water, fish, and shellfish from five locations with a typical mangrove environment. All samples underwent genomic DNA extraction, quantification, gel documentation, and subsequent sequencing. Sanger sequencing was then carried out, followed by sequencing 11 concentrated samples using the universal bacterial primer 16S rRNA. The study found 872 bacterial species, 94 genera, 38 families, and 6 phyla. Pseudomonades or proteobacteria accounted for 92% of the phylum composition, with firmicutes, bactericides, cyanobacteria, Verrucomicrobia, and actinobacteria also present at smaller percentages. Chromatiaceae had the highest species count (20.3%), followed by Ectothiorhodospiraceae (15.5%), Methylococcaceae (12.3%), Moraxellaceae (10.7%), Thiotrichaceae (8.7%), Idiomarinaceae (5.4%), and smaller groups. All the species that were identified were gram-negative bacteria and were found in different environments, mainly halophilic ones. Based on 16 s rRNA sequencing, additional experimental and clinical data, as well as NCBI (BLAST), approximately 49.3% of the 872 bacterial species are typically harmless and not classified as pathogenic. The pathogenic characteristics of 24.9% of the species are still unidentified. 13.4% showed either pathogenic or non-pathogenic characteristics (a bacterium as having the potential to exhibit pathogenic or non-pathogenic characteristics in certain circumstances), while 8.4% were exclusively pathogenic, potentially capable of causing disease. Also, the bacterial species are categorized as 2.6% non-highly pathogenic (a bacterium can still have a significant impact on health, especially in weakened immune systems or other underlying health conditions), 1.3% sometimes pathogenic and 0.1% potentially pathogenic (a bacterium don't always cause disease). Sequence analysis, combination of phylogenetic, biochemical characterization (data were not shown), and other experimental validation conclude a genetic baseline of bacterial community, this research may serve as a valuable reference for future ecological and taxonomical studies as well as addressing further research scope on bacterial diversity found in the Sundarbans mangrove of Bangladesh

Bacteriophage and non-pathogenic Vibrio to control diseases in shrimp aquaculture

The study aimed to address the recurring outbreaks of microbial diseases in shrimp aquaculture in Bangladesh the study focused on the utilization of bacteriophages and non-pathogenic Vibrio. The bacteriophages were isolated from sewage water sample collected from shrimp farm, hatchery, and the JUST campus. The bacteriophages were tested for their ability to infect different Vibrio strains in order to assess their bacteriolytic activity. Non-pathogenic Vibrio strains were obtained from suspected diseased isolates collected from the south-western region of Bangladesh through PCR amplification. In laboratory tests, the bacteriophages successfully infected 91 % of the tested Vibrio strains (19 out of 21 strains). In the experimental unit, shrimp treated with phage prophylaxis and phage treatment demonstrated notable protection against AHPND and was able to survive a deadly bacterial challenge. A total of 35 suspected diseased isolates were tested, and PCR amplification revealed 6 non-pathogenic Vibrio strains. In field trials, cultured bacteriophages were applied at a concentration of 1.5×106 PFU/ml, while non-pathogenic Vibrio was applied at 5×105 CFU/ml. The trials showed increased protection against infections and no severe deaths during the adaptive research phase. The cultured shrimp were analyzed morphologically and showed a muscle gut ratio greater than 4:1. No abnormal deformities were observed in their appendages or overall body, suggesting their overall health and well-being. The bacteriological tests conducted on the shrimp samples (application of bacteriophages and non-pathogenic Vibrio) revealed that 18 % of them were infected with bacteria, primarily Vibrio cholerae, Vibrio parahaemolyticus, and other bacterial species. Despite this, the infections did not lead to a disease outbreak; PCR amplification showed negative results for AHPND, White Spot Syndrome Virus (WSSV), and Enterocytozoon hepatopenaei (EHP). The results highlight the potential of using bacteriophages and non-pathogenic Vibrio as a sustainable solution for preventing and controlling microbial diseases in shrimp aquaculture. Furthermore, this study will contribute valuable insights into the development of alternative strategies to combat antibiotic resistance and promote the growth of the shrimp industry in Bangladesh