As Mycobacteriosis has become topical again I took the liberty of forwarding
some of the comments to Steve Pyecroft and his response follows
Regards,
Bruce.
Bruce Hansen, A.N.G.F.A., Advancing Australian Aquatics.
From: StephenPyecroft <fishdoc at rainbow.net.au>
To: Bruce Hansen <bruceh at powerup.com.au>
Sent: Tuesday, 8 June 1999 11:34
Subject: Re: Fw: [RML] mycobacteriosis messages
> Dear Bruce,
>
> Interesting comments re TB.
> I'm not quite sure what the distinction is between TB and MB as a disease
> entity basically if there are mycobacteria species present in conjunction
> with clinical signs you have a problem. Mycobacteria are in fact
> ubiquitous in the soil and water as you know and in my clinical experience
> high levels of organic matter and poor tank management seems to be top of
> the list for predisposition of established tanks, without introductions,
> developing the problem. If seemingly established tanks develop the problem
> without introductions then there is a fare chance that alatently infected
> fish has been present and either it has become clinically affected or an
> immune suppressed fish has then aquired the infection and then become
> clinically affected.
>
> Diagnosis and treatment are the greatest challenges with mycobacterial
> infections. Diagnosis as stated in the notes you sent me is best done on
> live fish and if the pathology is advanced and the organisms are
plentifull
> then they will be identified readily. If however the lesions are
> developing and the organism numbers are low then in fact it can be
> difficult to positively diagnose a mycobacterial infection, even when
> utilising histopathology and special stains such as Zeil-Neilsen acid-fast
> stain.
>
> PCR primers have been developed so that diagnosis can be made on live
fish.
> This allows fish to be introduced to the display or breeding stocks
> individually once they have been cleared. Diagnosis at PM is open to
> misinterpretation due to the reasons already stated and even if you use
the
> best statistical basis there is still a slight chance that the one fish
> that will be introduced may still be latently infected. A clinically
> usable test is still being dveloped and so aquarists will have to wait a
> little longer before fish can be tested commercially.
>
> Treatment is also a challenge. As stated Kanamycin and Isoniozid can be
> used in combination for treatment but the take home message for treatment
> regimes is the agents must be applied long term and via an appropriate
> route. A bath medication for 5-10 days does not qualify. Sure there may
> be a cessation of clinical appearance of disease due to masking of signs
> but that does not constitute a cure. A cure can be claimed after
treatment
> only after a statistically sound number of fish are subjected to testing
so
> that a high probability of detection is acertained. The restrictions of
> this sort of testing have already been mentioned. PCR will make it
easier.
>
> Immune suppresion, poor environment and the presence of the appropriate
> bacteria are the key features for infection. The bacteria once clinically
> active is usually spread via fomites and infected fish and if these
animals
> die and are eaten they are the best and most affective transfer of
bacteria
> from fish to fish. The air bourne transfer of aquatic mycobacteria would
> be pretty low on the 'possibilities list' for introduction to an
> established tank as there are far more common ways to have the bacteria
> present than that. Latently infected fish is top of the list.
>
> Anyway must get back to the paid work now hope these are usefull comments.
>
> Cheers
> Dr. Stephen B. Pyecroft BVSc Hons
> Director
>
> Aquatic Diagnostic Services International Pty Ltd
> Lab: 14 Gordon Parade
> Everton Park
> Q4053
> Brisbane, Australia.
> Phone: 61-7-38552333
> Fax: 61-7-33542149
> Mobile: 0414478630
> Email: fishdoc at adsi.com.au
> website: www.adsi.com.au
>