[Zbrafish] Aeromonas spp.--is this something to worry about?

christian lawrence via zbrafish%40net.bio.net (by clawrence from rics.bwh.harvard.edu)
Mon Jun 25 13:03:48 EST 2007


Rebecca,

Without knowing the particulars of your situation I would say the following:
Don't panic.

Aeromonas sp. is very common in this type of aquatic system.  It is
opportunistic, affecting fish that have some compromise in their immune
function.  This could be stress caused by various things, most notably poor
environmental conditions.  It could also simply be that the fish are old
(immune function decreases with age) or have some genotype that weakens
immunity.  In some cases, it might be a secondary infection to some other
pathogen.

A few fish out of a population of thousands suggests that it is simply
attrition that you're seeing.  The key is to monitor deaths.  

If you see only a few fish at any one time with this phenotype, then it is
probably simply normal.  The fish have to die from something, and if you did
pathology on every mortality, you would likely turn up bacteria like
Areomonas every time.  In this case, it doesn't mean much.  It is just one
of the very many opportunistic nasties that are lurking out there that can
exploit weak fish.  Sort of like how the lion preferentially hunts the
young, sick, and old.  This is normal and to be expected.

If however, you see sharp, drastic increases in numbers of mortalities
(above baseline) then you should start to worry a bit.  The first thing to
do if this were the case would be to absolutely ensure that your water
quality and diet are good (in most cases this is the underlying problem) and
then go from there.

Most bacterial pathogens like Aeromonas are never a real threat to your fish
populations unless your husbandry is sub-standard.  If your fish are happy,
you don't have much to worry about.  If not, then they are a very serious
threat.  In almost all cases, good husbandry is the difference.

Let me know if you have further questions, and I will be glad to help out.

Chris

Christian Lawrence
Brigham and Women's Hospital
Karp Family Research Laboratories 06-004B
One Blackfan Circle
Boston, Massachusetts 02115
Tel: 617.355.9041
Fax: 617.355.9064

-----Original Message-----
From: zbrafish-bounces from oat.bio.indiana.edu
[mailto:zbrafish-bounces from oat.bio.indiana.edu] On Behalf Of lampe1 from umbc.edu
Sent: Monday, June 25, 2007 12:04 PM
To: bionet-organisms-zebrafish from moderators.isc.org
Subject: [Zbrafish] Aeromonas spp.--is this something to worry about?

Hello!

I am a technician at a zebrafish facility with approximately 5000 fish.
Recently, a few of our fish have gotten extremely swollen abdomens and no
longer reproduce. A vet came in and did some tests on two sick fish. His
diagnosis was Aeromonas spp. We were sent some info on Aeromonas and from
what I understand, it is a normal bacteria living in the fish.

Am I correct in this understanding? Should I be worried or need to start
treating the fish? Or is the vet's diagnosis useless because all of our fish
would test positive for Aeromonas (and maybe he did not understand this
because he is not too familiar with zfish)?

Thanks for any help!

Rebecca Lampe
Laboratory Animal Technician
UMBC Biology Department
Brewster Lab
410-455-6322

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