[Zbrafish] Re: Microsporidiosis

Katy via zbrafish%40net.bio.net (by kbaden from gmail.com)
Mon Jun 30 12:38:17 EST 2008

On Jun 25, 10:32 am, sarah <sspine... from ric.edu> wrote:
> I suspect that we may have some fish with Microsporidiosis infection.>From reading that I have done it seems that I should euthenize ALL of
> the fish in the AHAB benchtop system and empty all water and clean all
> tanks and resevoir. But I have also read that this parasite may not be
> killed by common disinfection agents. How can I completely rid the
> system of this agent? can things be taken apart and autoclaved? Has
> anyone else encountered this and what did you do?  PLEASE HELP!!!

Hi Sarah,
First, I would confirm that you do in fact have microsporidiosis
(Pseudoloma neurophilia) in your zebrafish.  Almost any pathogen can
result in a skinny fish and there is no pre-mortem diagnostic for
Pseudoloma in zebrafish.  You can diagnose microsporidiosis in H&E
stained histological sections, wet mounts of the spinal cord and
brain, or by PCR on spinal cord and brain tissue.

Bleach concentrations used to sanitize eggs are not effective against
Pseudoloma spores.  However, high concentrations of pH adjusted bleach
will kill the spores.  See Ferguson et al. (2007), Dis Aquat Org, Vol.
76: 205-214.  Bleach is toxic to zebrafish, causing acute gill
necrosis and asphyxiation.  Therefore, it's important to neutralize
with sodium thiosulfate and rinse well.   Having said that, the most
likely, and proven, mode of transmission is by cannibalism of dead,
infected fish.  Therefore, removing dead, old, and sick fish from your
population is the most effective way to break the cycle of
transmission.  I am not aware of Pseudoloma being detected in biofilms
and have not personally been able to detect it in water or debris
samples from tanks with infected fish.

UV is also an effective means of killing Pseudoloma spores.  Have you
checked the efficacy of your UV bulbs?  I suspect that dead fish can
get pulverized in the drains and filtration system, liberating
infective spores.  However, UV will kill the spores and prevent
circulation of Pseudoloma throughout your system.

Katy Murray DVM, Ph.D.
Zebrafish International Resource Center

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