ORCID Profile
0000-0002-5144-263X
Current Organisations
University of Tasmania
,
Biofeyn Inc.
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Publisher: Elsevier BV
Date: 2016
DOI: 10.1016/J.VACCINE.2015.12.044
Abstract: Yersinia ruckeri is a ubiquitous pathogen of finfish capable of causing major mortalities in farmed fish stocks. It can be transmitted vertically from parent to progeny as well as horizontally in the water column from both clinically infected fish and asymptomatic carriers, and is consequently capable of infecting fish at early stages of development. Immunisation strategies that can protect small fry are therefore critical for the effective management of fish health, as is the ability to detect covertly infected fish. In this study, first-feeding Atlantic salmon fry (<0.5 g) were immunised either by oral administration of a microencapsulated Y. ruckeri vaccine formulation (0.38 g initial weight), or via immersion in bacterin suspension (0.26 g), with and without a booster immersion vaccination at 1g size. Protection in groups receiving only immersion immunisation did not differ significantly from untreated controls when challenged with Y. ruckeri at approximately 5 g size, while orally immunised fish were significantly better protected than untreated controls (F=4.38, df=4,10, P=0.026), with RPS varying between 29.4% (ORAL) and 51% (ORAL+DIP). A quantitative real-time PCR assay was used to successfully detect covertly infected fish among challenge survivors, indicating more than 50% of surviving fish in each group were infected with no significant differences between immunised fish and untreated controls.
Publisher: Wiley
Date: 10-2016
DOI: 10.1111/JFD.12311
Abstract: Flavobacterium psychrophilum is the causative agent of bacterial coldwater disease (BCWD), which has a major impact on salmonid aquaculture globally. An Enterobacter species, C6-6, isolated from the gut of rainbow trout, Oncorhynchus mykiss (Walbaum), has been identified as a potential probiotic species providing protection against BCWD. This study examined the effects of alginate microencapsulation on the protective efficacy of C6-6 against BCWD in vivo when administered to rainbow trout fry orally or by intraperitoneal (IP) injection. Viable C6-6 bacteria were microencapsulated successfully, and this process (microencapsulation) did not significantly deteriorate its protective properties as compared to the administration of non-microencapsulated C6-6 bacteria. Both oral and IP delivery of C6-6 achieved significantly better protection than control treatments that did not contain C6-6 bacteria. The highest relative percent survival (RPS) resulted from IP delivery (71.4%) and was significantly greater than the highest oral RPS (38.6%). Successful intestinal colonization was not critical to protective effects of C6-6. The study showed that C6-6 administration, with or without encapsulation, was a viable choice for protecting fry from BCWD especially when administered intraperitoneally.
Publisher: Elsevier BV
Date: 05-2022
DOI: 10.1016/J.FSI.2022.03.024
Abstract: Little is known about host responses of farmed Chinook salmon with skin lesions, despite the lesions being associated with increased water temperatures and elevated mortality rates. To address this shortfall, a transcriptomic approach was used to characterise the molecular landscape of spot lesions, the most commonly reported lesion type in New Zealand Chinook salmon, versus healthy appearing skin in fish with and without spot lesions. Many biological (gene ontology) pathways were enriched in lesion adjacent tissue, relative to control skin tissue, including proteolysis, fin regeneration, calcium ion binding, mitochondrial transport, actin cytoskeleton organisation, epithelium development, and tissue development. In terms of specific transcripts of interest, pro-inflammatory cytokines (interleukin 1β and tumour necrosis factor), annexin A1, mucin 2, and calreticulin were upregulated, while cathepsin H, mucin 5AC, and perforin 1 were downregulated in lesion tissue. In some instances, changes in gene expression were consistent between lesion and healthy appearing skin from the same fish relative to lesion free fish, suggesting that host responses weren't limited to the site of the lesion. Goblet cell density in skin histological sections was not different between skin s le types. Collectively, these results provide insights into the physiological changes associated with common spot lesions in farmed Chinook salmon.
Publisher: Springer Science and Business Media LLC
Date: 26-09-2015
DOI: 10.1007/S10126-015-9663-7
Abstract: This study examined the feasibility of alginate microcapsules manufactured using a low-impact technology and reagents to protect orally delivered immunogens for use as immunoprophylactics for fish. Physical characteristics and protein release kinetics of the microcapsules were examined at different pH and temperature levels using a microencapsulated model protein, bovine serum albumin (BSA). Impact of the microencapsulation process on contents was determined by analysing change in bioactivity of microencapsulated lysozyme. Feasibility of the method for oral immunoprophylaxis of finfish was assessed using FITC-labelled microcapsules. These were applied to distal intestinal explants of Atlantic salmon (Salmo salar) to investigate uptake ex vivo. Systemic distribution of microcapsules was investigated by oral administration of FITC-labelled microcapsules to Atlantic salmon fry by incorporating into feed. The microcapsules produced were structurally robust and retained surface integrity, with a modal size distribution of 250-750 nm and a tendency to aggregate. Entrapment efficiency of microencapsulation was 51.2 % for BSA and 43.2 % in the case of lysozyme. Microcapsules demonstrated controlled release of protein, which increased with increasing pH or temperature, and the process had no significant negative effect on bioactivity of lysozyme. Uptake of fluorescent-labelled microcapsules was clearly demonstrated by intestinal explants over a 24-h period. Evidence of microcapsules was found in the intestine, spleen, kidney and liver of fry following oral administration. Amenability of the microcapsules to intestinal uptake and distribution reinforced the strong potential for use of this microencapsulation method in oral immunoprophylaxis of finfish using sensitive immunogenic substances.
Publisher: Wiley
Date: 21-06-2018
DOI: 10.1111/JFD.12839
Abstract: Finfish with asymptomatic Yersinia ruckeri infections pose a major risk as they can transmit the pathogen and cause clinical outbreaks in stock populations. Current tools have insufficient quantitative ability for accurately detecting the trace levels of Y. ruckeri typically associated with asymptomatic infection, necessitate invasive or lethal s ling, or require long processing times. This study presents a highly sensitive qPCR-based method, targeting part of the Y. ruckeri 16S rRNA sequence, that is capable of detecting extremely low levels of Y. ruckeri in noninvasively collected faecal s les. Quantitative precision and accuracy of faecal s le analysis was consistent, despite the complexity of the faecal matrix. The assay demonstrated linearity over a six log-wide dynamic range. Its limit of detection (LOD) and limit of quantification (LOQ) were 4 and 10 copies of the target sequence, respectively. Sensitivity of the assay was comparable to other qPCR-based methods without requiring invasive or lethal s ling. Applicability as a screening strategy was tested using passively collected faecal s les. Asymptomatic Y. ruckeri infection was detected in all s les, although none of the fish exhibited overt infection. This method will be beneficial for finfish disease management if developed further as a noninvasive, screening tool against asymptomatic Y. ruckeri infection.
Publisher: Elsevier BV
Date: 09-2015
No related grants have been discovered for Bikramjit Ghosh.