Exploring the potential of probiotics in disease management of shrimp production in Viet Nam. (IRO scholarship)
Description: Viral and bacterial epizootics are considered as major limiting factor and constraints for the successful development and continuation of shrimp aquaculture production in terms of quality,quantity and regularity. Broad spectrum antibiotics have extensively been used as a means of reactive disease management strategy in aquaculture facilities. However, excessive antibiotic use can lead to the emergence of bacterial resistance.
It has been reported that both health and survival of organisms in
intensive rearing systems could be improved substantially by manipulating the gut / environmental microbiota with probiotic microorganisms and/or prebiotics,
which can be added to the diet and/or to the environment to promote the growth of beneficial bacteria in the gastrointestinal tract of the animal as well as in the detritivorous microbes in the pond bottom. The use of probiotics for disease prevention and improved nutrition in aquaculture is becoming increasingly popular due to an increasing demand for environment-friendly aquaculture.
Shrimp cultivation is one of the biggest farming industries in Viet Nam, especially in the Mekong Delta. Cultivating of shrimp is now facing a lot of problems due to infection diseases. Those diseases can be more or less controlled by using antibiotic treatments. However, the worries of selecting antibiotic resistant pathogens when applying antibiotics for a long time as well as influences to human health are the major public concerns. The latter can lead to losing exporting market and thus cause dramatic economic loss. An alternative way to interfere with pathogenesis is to stimulate the immune responses of shrimps. This prevention approach can be achieved by either vaccination or utilizing of probiotics. The latter use has received more and more attention in the past three years due to its advantages in environmental friendliness and other positive effects. It has been proposed that probiotics can help in stimulating shrimps¡¦ immune systems as well as improving shrimp¡¦s growth. In Viet Nam, application of probiotics on aquaculture has received more and more attention. However, information about probiotics application on shrimp cultivation is scanty and there has not been any comprehensive study to evaluate the effects of probiotics isolated from shrimp to the shrimp pond.
OVERALL OBJECTIVE
With this project, we aim to isolate possible probiotics from black tiger shrimp Penaeus monodon and evaluate their effects on shrimp growth, especially in disease management. Information from this study can help in improving the quality of shrimp produced and contribute to develop a sustainable shrimp production industry.
PROJECT OUTLINE
The Ph.D project consists of four work packages (WP).
WP 1: Isolation and identification of lactic acid bacteria from shrimp
Samples will be collected from local shrimp farms, whereby the farmers will also be asked to fill out a questionaire aiming to obtain information on the past and current farmers¡¦ practices to control bacterial diseases. We expect to include a large number of shrimp farms. Bacterial isolation is initially biased towards Lactobacillus species as this species is well known for its probiotic activity in terrestrial systems and is a major focus of research at the Centre of Microbial and Plant Genetics. Possibly, the screening will be extended to more genera of the lactic acid bacteria (LAB). Strains plated out from shrimp gut (or from shrimp in general) will be preliminarily tested for their antagonistic effects against shrimp pathogens (Vibrio for example). Lactobacillus sp. and LAB in general, will be isolated by putting the bacteria on selective medium.
WP 2: Structural and functional characterization of the isolated probiotic strains
Structural: the isloated strains will be taxonomically characterized based on 16S rDNA sequencing. This will allow identification to the species level.
Functional: a recently developed functional gene array for LAB will be used. This will allow us to make a selection of strains that potentially will perform best in relation to probiotic characteristics.
WP 3: Determining mode of action in vitro
The main screening in vitro is directed towards antimicrobial activity of the selected lactic acid bacteria for which one or two well established protocols to show antagonism towards the main shrimp intestinal pathogens (Vibrio and Aeromonas species) will be used. In addition, as Vibrio and Aeromonas species are well known for their quorum sensing systems, we will also test whether the isolated probiont strains can interfere with these QS systems (AI-2 type) thereby affecting also their pathogenicity.
WP 4: Immunomodulatory activity of isolated probiotics
Probiotic Lactobacillus strains are known to interact with the immune system of terrestrial organisms (human, murine, avian). Indirectly, this results in some cases in better protection against pathogenic bacteria. We will set up an in vivo system to study the immunomodulatory effect of the selected LAB in shrimp (and possibly related aquatic organisms that can be easily cultured in lab scale conditions). Immunomodulatory activities will be tested by PCR and ELISA techniques. In addition, the following parameters will be monitored: haemocyte counts, PO activity, SOD activity and clearance efficiency in challenging tests.
Lastly, follow-up activities are also planned:
ƒ{Investigating gastrointestinal microbiota composition of adult shrimps previously dieted with probiotics
ƒ{Investigating growth and immune status against pathogens at different time points after probiotic administration
ƒ{Tracking effects of probiotics on subsequent shrimp larvae
Key words: Shrimp aquaculture, disease management, probiotics, healthy and sustainable production, Mekong Delta, Viet Nam
Latest application date: 2009-12-31
Financing: iro-scholarship
Type of Position: scholarship
Source of Funding: IRO
Duration of the Project : 4 years
Research group: Department of Microbial and Molecular Systems (M#S)
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