Industrial aquaculture is a rapidly growing industry in almost every
region of the world. Depletion of fisheries and the market forces that globalize
sources of food supply are expected to stimulate an even faster growth rate of
the aquaculture industry in the future. However this impressive industrial
development has been accompanied by some practices potentially damaging to
human and animal health that include passing large amounts of Vetinary drugs
into the environment, resulting in an increase of antibiotic resistant bacteria
and fish pathogens. Effective use of prophylactics in aquaculture is therefore
undermined and increases the possibility of transferring this resistance to
bacteria (including pathogens) of terrestrial animals and humans, proof of which
has recently been shown in a number of studies.
Antibiotics are administered to fish as a component of their food and
occasionally by injection or baths. Unconsumed food and faeces containing
antibiotics reaches the sediment at the bottom of the fish enclosure where the antibiotics
are leached from the food and faeces and diffuse into the sediment where they
can be washed away by currents to distant sites and potentially ingested by
wild fish and other organisms. Antibiotics that are not washed away exert selective
pressure on the microflora of the sediment, altering the composition and selecting
for antibiotic resistant bacteria. The author describes the results of many
studies supporting the concept that antibiotic usage in aquaculture will influence
the appearance of resistance in bacteria of other niches, including resistance
to pathogens able to produce a variety of animal and human diseases.
Residual antibiotics in commercialized fish and shellfish products are
another problem created by extensive antibiotic use in aquaculture. If undetected,
potential alteration of the consumer’s natural flora may occur, increasing
their susceptibility to bacterial infections and also selecting for antibiotic
resistant bacteria. Problems related to allergies and toxicity may also occur.
As a result of the many studies into the effect and potential results of
excessive antibiotic administration in aquaculture, many countries around the world
have implemented drastic restrictions on antibiotic use and attention is now
turning to the use of vaccines to cure and prevent many of the bacterial
diseases commonly contracted by fish in aquaculture. However some countries,
such as Chile and China have increased antibiotic use in recent years, form 30
tonnes to close to 100 tonnes as antibiotic use is still totally unrestricted.
This review is rather short but does bring together and summarize a
large amount of research into the effects of antibiotic use in aquaculture with
particular emphasis on wild microbial populations and potential effects on
humans. However, it does not go into detail about how antibiotic consumption
can have negative impacts on cultured fish and shellfish by ultimately decreasing
the effectiveness of their immune system and therefore making them more
susceptible to infections.
5 comments:
that is a good point that antibiotics generally wipe out a range of bacteria and can leave a fish without the correct balance for digesting food properly. This is why the use of probiotics could be so good in that they protect and can replace lost bacteria to maintain a healthy gut microbiota. That would work like the vaccines to prevent disease which is the most effective way forward. china does use probiotics too, i guess they are using more antibiotics because they have more aquaculture.
I thought that there was a lot of controversy over the use of probiotics. A while ago I remember an article questioning the efficacy of probiotic supplements. I have just done a quick Google search and found a useful document on the use of probiotics in aquaculture. It mainly refers to the use of probiotics in shrimp aquaculture. It mentions that the benefits are not only seen directly on the shrimp but also in the water and sediment quality which reduces stress on shrimp increasing their overall health. Here is the link if you want to have a look
http://www.inve.com/binarydata.aspx?type=doc/Probiotics_in_aquaculture.pdf
This seems to be a great area of debate. Link below is an interview of a representative for the FDA, an arm of the US government which monitors the application of drugs in agriculture. It is non-specific video including many species important in agriculture, so unfortunately aquaculture is only briefly mentioned. However, it does give a useful insight in to the scale of the use of antibiotics and the processes that are needed to safely introduce and develop antibiotics for use with animals. It outlines the processes involved with drugs in ecological management as well as the wider considerations of human safety issues and economic impact.
http://www.youtube.com/watch?v=5GGnYCIbYl0
i think lots of people thought that probiotics were the answer to preventing all kinds of diseases and infections in aquaculture but now the effects of probiotics that dont get eaten are seen in the environment and its not good - better than antibiotics but still not good so attention is now on prebiotics to come to the rescue. prebiotics dont contain live microorganisms like probiotics do, but are things like oligosaccharides with beta-linked subunits that the fishes enzymes cant digest but they can be digested by the nice helpfull gut microbiota they contain, encouraging their growth and proliferation. the more helfull and friendly bacteria there are in the gut the less chance nasty bacteria and virus have of finding attachment sites and nutrients and stuff. its a lot more complicated tha that but i think its the general gist!
probiotics can have a wide range of benifits and being alive they can potential remain to continue the good work, rather than having to continuously add more stuff like antibiotics and prebiotics. However evidence suggests that the probiotics do need to be regularly fed. Also the live probiotics are yet another, possibly foreign bacteria being added to the environment and some probiotics are closely related to pathogens!
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