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Re: "tossing fish in ponds"

At 09:38 PM 8/31/99 +0100, you wrote:
>I have heard that the Nothobranchius ailment of a burrowing worm which, in
>its later stages burrows to the stomach wall & causes white lumps on the
>sides was originally started off by putting fish in outdoor ponds.
>I have known a few people get it & have had to strip down there fish houses
>as it is supposed to be transfered on the egg shell.
>Has anyone heard anything about this & is it true.
>I understand diluted formalin used to wash the eggs works.
>

Tim

First, the organism to which you refer is not a worm and does not burrow.
It is a protozoal parasite of the genus Glugea. It has been tenatively
identified as Glugea anomala, but that is not definitive because the
identification was on the basis of morphologic similarities. The mechanism
of entry of this parasite is unclear, but it probably enters through the
intestinal tract after the fish ingests spores. The organism enters host
(ie. fish) cells and replicates, greatly expanding the size of the cells.
Aggregates of these cells form the while granules or lumps that may become
grossly visible (but are not necessarily so). G. anomala is a parasite of
sticklebacks, and while it is appealing to hypothesize that Nothos may have
become infected by keeping them in outside ponds, I know of no definitive
evidence to support it. Nevertheless, it could happen and your implied
general warning about bringing infections or parasites back into the
fishroom is valid.

You comment that Glugea is very difficult to eliminate, once in a fishroom,
is true. Getting rid of all fish, sterilizing everything, and starting
again may be the only sure approach. The idea of washing the eggs with
dilute formalin is appealing, so I tried it and could not convince myself
of its efficacy. The difference in formalin concentration between killing
Glugea spores on the eggs and killing the eggs may be too narrow.

There is one ray of hope for this problem. There are recent reports in the
literature that treatment of sticklebacks infested with Glugea anomala with
anthelmintic drugs of the benzimidazole type (albendazole, mebendazole and
fenbendazole) can cure the infection. These studies even suggested that
such treatment could decontaminate eggs. As far as I know, nobody has
systematically treated killies infected with Glugea with these drugs. If
anyone knows that they have this problem in their fishrooms, I would be
glad to advise them on an approach to testing the treatment (which would
involve confirming the infection is present, then setting up treated and
non-treated control groups, then evaluating the infection
histopathologically). It would be very useful to definitively prove that
this treatment works and proper controls are important. I will say that I
worked with one hobbyist who had seen this infection in some of his fish
(histologically confirmed). He treated some others, but when I studied them
I found that the pre-treatment group did not have Glugea after all, so no
conclusions could be drawn from that group. In other words, it is
insufficient to say that "I had Glugea, and I tried X and it worked" unless
you have proven that you really had that specific problem and that it
really worked. Other things can cause white lumps in fish!

Finally, Nothos are not the only killies that can be infected by Glugea. I
have seen it in specimens of South American annuals and in Fundulopanchax.
Nothos do seem, however, to be particularly susceptible.

Regards,

Barry
Barry J. Cooper				Currently in Oregon:
Prof., Dept. Biomedical Sciences		27505 Riggs Hill Rd.
Cornell University				Sweet Home, OR 97386
(607)253-3304				(541)367-2568
bjc3 at cornell_edu				bjc3 at cornell_edu
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