THE PROBIOTIC CONCEPT
From: Pablo Legarda sffarming@yahoo.com
To: shrimp@yahoogroups.com
Sent: 14 October 2004
It is important to remember some facts about bacteria
in the aquatic environment. In estuarine environments and published
work in shrimp ponds, bacteria concentration in water and soil ranged
from 10^6 to 10^7 in water and 10^8 to 10^9 in soil. Evacuation time
in shrimp ranged from 10 min in larvae to 6 hours (roughly) in broodstock.
Some probiotics include yeast in their mix (baker yeast!), yeast walls are
undigested by shrimp enzymes, likewise some spores and bacteria cell walls.
1. Could a commercial broth of probiotics be competitive enough to
outnumber local bacteria (specially considering that commercial
bacteria are used to rich organic grow media (fat large cells) and the
aquatic environment is rather poor (small starved and sometimes non
culturable but viable cells).
2. Is the decaying rate of the probiotic strains used in aquaculture lower
or higher than native bacteria?
3. Probiotics such as the one present in yoghurt, are supposed to outnumber
attached bacteria in the intestines of hosts (by competitive exclusion, one
of the original description of probiotics used in poultry, humans, et). Can
bacteria attach to and colonize shrimp intestines?
4. Finally some bacillus strain can also cause disease in shrimp
and even similar to WSSV, see report in DAO http://www.int-res.com/abstracts/dao/v41/n1/p9-18.html).
Pablo Legarda
e-mail: sffarming@yahoo.com
***************
COMMENTS 1:
You are right to be concerned about the safety of the
bacteria used
as probiotics. Those who attended my talk about probiotics at the
recent Australasian Aquaculture 2004 conference will know that this
point was emphasised.
However, in relation to the safety of Bacillus subtilis, if you have
a close look at the abstract you listed (relating to the bacterial
white spot syndrome), you won't find any causative link between use
of Bacillus subtilis and the so-called syndrome. Please see the
Aquatic Animal Pathogen and Quarantine Information System (AAPQIS), which
clearly explains this (please see
http://www.aapqis.org/main/path/viewpath.asp?PathID=57).
Bacillus subtilis is on the GRAS (generally regarded as safe) list of
the USFDA.
There are two ways you can be sure that Bacillus probiotics are safe
for your stock and your workers:
- Most importantly, a history of safe use in aquaculture.
- Demonstration of the absence of genes that could be associated
with virulence.
Kevin Healey
e-mail: khealey@iahp.com.au
www.iahp.com.au
***************
COMMENTS 2:
Yes, I am sorry I meant it
+ can affect shrimp (diseased or affected, even
though white spots disappear after molting) such as the one described in
that report in DAO. But again there are several issues not covered by
commercials and eventually will turn the discussion to a non-scientific
issue.
Pablo Legarda
e-mail: sffarming@yahoo.com
***************
COMMENTS 3:
The AAPQIS database clearly shows there is no
causative link between
the "syndrome" and Bacillus subtilis. As far as i can tell from
the
DAO abstract (the full text isn't available on-line), there's
nothing to link the subtilis with any kind of deleterious effects on
shrimp (whether healthy or already weakened by disease). If there
was subtilis in the water, and the lesions had open centres
(allowing access to bacteria from the water column), then it would
be more remarkable if there was NOT subtilis within the lesions. For
all we know, if the subtilis had not been present, the lesions might
instead have been full of Vibrio, as the AAPQIS listing tends to
suggest.
The most pleasing thing is to see the level of interest in the
current exchanges about probiotics; positive or negative, it raises
awareness and stimulates interest. If the next time a shrimp farmer
or hatchery technician is tempted to reach for an antibiotic or a
biocide he or she stops for a moment and ponders whether probiotics
might offer an alternative, then the industry will have been well-
served.
As a representative of a commercial supplier of probiotics, I am the
first to admit that we don't have all the answers to the questions
you and others have raised. This isn't so surprising; if you
consider the other intensive animal industries like poultry, pig and
cattle raising, there are still plenty of unanswered questions
despite the massive amounts of resources and research that have been
poured into these industries all around the world over many
generations. These industries still experience losses due to
disease, and even the most experienced veterinarians still have do
deal with cases where they can't make a certain diagnosis or be sure
that a particular therapy will be effective. Yet compared to these
industries, commercial shrimp farming is at a much more pioneering
stage.
Kevin Healey
e-mail: khealey@iahp.com.au
www.iahp.com.au