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Fish TB
Hello, all.
Just a few words on the recent thread of fish TB (Mycobacteria). There
were a few questions about diagnosis and treatment. Primary clinical signs for
fish TB are emaciation, poor growth, and retarded sexual maturation. Skeletal
deformities (esp. lordosis or dorsoventral spinal curvature) and chronic,
unhealing ulcers are also common. If you want to necropsy any of your dead
fish that you suspect, look for 1 to 4 mm white nodules on liver or spleen,
esp. if these organs are enlarged. Histologic exam is really the best way to
definitively diagnose Mycobacteria, but that is well beyond the reach of most
who do not want to send their fish to a veterinary or medical clinical center.
Mycobacteria is very common in wild fish, but usually is maintained at a
subclinical level, not causing patent disease. Chances are pretty good that a
few of the fish in your tanks right now are carriers. These bacteria generally
only cause disease under suboptimal conditions, so an ounce of prevention (in
the form of clean tanks) is worth a pound of cure. Others have been doing a
good job of discussing antibiotic strategies, so I won't go into that.
Quarantine and/or destruction of infected (or suspect-infected) fish are
indicated, depending on your willingness to experiment with different
antibiotics.--One antibiotic that I have not seen mentioned in the thread is
Kanamycin,
which may be effective in some cases [Conroy & Solano (1965), J Fish Res
Brd Can 22:243-245].
A good reference for those more interested in fish disease is Noga (1996) Fish
Disease: Diagnosis and Treatment.
Regards
Dave Gauthier
gauthie9 at pilot_msu.edu