prevalence and molecular characteristics of vibrio species in pre ...

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genes by DNA based molecular techniques such as PCR and colony hybridization
methods are more important. Researchers found the PCR method as a more reliable,
rapid and sensitive method compare to conventional microbiological assays (Bej et
al., 1999, Raghunath et al., 2008).
2.10 Prevention and control of Vibrio in shrimp production chain
2.10.1 Pre harvest stage
2.10.1.1 Biosecurity measures
With an expanding aquaculture industry, appropriate techniques are required to
mitigate diseases. With new technologies, biosecurity measures can easily be adapted
for small or large scales farms. Biosecurity is defined as the practices that reduce the
probability of pathogen introduction and control the subsequent spread from one place
to another. The primary goal of biosecurity in shrimp farming is to prevent entry of
infectious organisms into the farm. Possible carriers are, (i) infected host (post larvae,
brood stock); (ii) non-host biological carriers (contaminated water); (iii) inanimate
objects contaminated with pathogens (vehicles, human, nets) (Lotz, 1997). A sound
biosecurity program of a shrimp farm includes disease prevention, disease monitoring,
management of disease outbreak, cleaning, disinfection and general security
preventions.
Perera et al. (2008) recommended measures can be taken to minimize the
input of pathogens into the farm. For example, stocks (brooding/post larvae) can be
obtained from populations of specific pathogen free or specific pathogen resistance
stock or populations subject to monitoring and known to be in good health, or
quarantined and tested or treated to reduce the risk. Pathogen transmission by feed can
be controlled by providing commercial pelletized feed that are subjected to a degree
of pathogen inactivation by heat generated through the process of extrusion and pellet
drying (Perera et al., 2008). Water is the major non-living conveyer of the pathogens.
Pathogens may be present in the incoming water because of the presence of natural