[Zbrafish] Mycobacteria

christian lawrence via zbrafish%40net.bio.net (by clawrence At rics.bwh.harvard.edu)
Tue Jan 23 12:07:16 EST 2007


The veterinarians that monitor this list may have different opinions on how
to proceed (and correct me if I have made technical misstatements), but I
would make the following GENERAL statements, based on experience:

1. If Mycobacteriosis is in your system, it is difficult, if not impossible
to eliminate without "nuking" the system: sacrificing all of the fish,
breaking down and sterilizing the system and components and starting over
with SPF (or at least Myco free) fish.

2. If a facility has has Myco in the past, and it hasn't been "nuked", it
still has Myco, even if things have since "cleared up" (no mass
mortalities).

3. I think it not a crazy to guess that many populations of fish from
long-term facilities carry one or more strains of Mycobacteriosis - even
though personnel may be completely and blissfully unaware of it (I would
love to see a wide-scale pathology study done on random samples from many
places).  The better the "conditions" (environment, diet, and genetics)the
more chronic, low level the presentation of these strains Myco will be (will
knock out only old or otherwise immunocompromised fish).  The worse the
conditions are, the more acute the outbreak.  If your fish experience a big
negative environmental effect, the low level, chronic Myco can easily become
an all-out severe outbreak.  

4. If you get fish from another lab, anywhere, that isn't certified SPF
(ZIRC is for certain diseases, including Myco, I think, but who else?) you
may very well be bringing in Myco, since as far as I know, bleaching eggs
(particularly the brief exposure typical of most protocols) is not 100%
effective at getting rid of it.

5. There may be problems if a different strain of Myco gets into a new
environment - from what I understand, the levels of virulence can depend on
the environment and populations infected. 


What does all of this mean, relative to your situation?  If you're having a
high level mortality event, and like most people, cannot afford to "nuke"
the system and start over, I would do my very best to ensure that ALL
environmental parameters are favorable and stable, cull aggressively, cut
back on feeding, slowly lower the temp a few degrees and maybe up the
salinity a bit and hope for the best.    If you're not experiencing high
level mortality, and routine pathology revealed that one of your normal,
baseline level morts was infected with Myco, it certainly isn't cause for a
dance party, but I wouldn't worry too much about it.  I would just strive to
ensure that husbandry protocols are optimal and stable and move on
(carefully).  

The fact that you say that you're trying to establish a colony suggests that
environmental parameters may not yet be stable.  If this is the case,
stabilization at favorable levels is absolutely key to solving the acute
mortality problems that you may be experiencing.

Good luck,
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 At oat.bio.indiana.edu
[mailto:zbrafish-bounces At oat.bio.indiana.edu] On Behalf Of
Padnos.Beth At epamail.epa.gov
Sent: Tuesday, January 23, 2007 11:08 AM
To: zbrafish At oat.bio.indiana.edu
Subject: [Zbrafish] Mycobacteria

I work in a facility that is trying to establish a small Medaka and Zebra
fish colony.
Recently we discovered Mycobacteria in our Medaka which are on the same rack
as our Zebrafish. One of the male Zebrafish  began swimming a bit oddly and
his abdomen became red as if bleeding internally or inflamed organs. He is
has since been set to the pathologist for screening, but is assumed to have
Mycobacteria as well.
The facility Veterinarian and I have both done literature searches but find
not treatment. Has anyone successfully treated or eliminated Mycobacteria
from their  fish and or system?
Help is greatly appreciated from an inexperienced fish researcher.
Beth Padnos

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