>Regarding the mycobacterium becoming 'airborne' I don't think this is true
>because otherwise losses and the number of infected humans would be
>substantially bigger?
My research has indicated that many species of mycobacteria can become
airborne including the ones usually associated with fish disease. They are
found almost everywhere. Most do not like the body temperature of humans and
this is the reason more humans do not become infected. Incidentally, the
human form of TB is once again on the rise here in Australia and also all
over the world. The WHO has actually issued an alarm at the increase in this
disease.
As for antibiotic treatment - Mycobacteria have a very high lipid content
and once in the body, are phagocytised by the macrophages. However, the
lipid coat makes them very resistant to destruction by the macrophages. So,
they live and possibly reproduces within the macrophage. This also protects
them from antibiotic treatment. Therefore you may be able to destroy the
bacteria in other parts of the body or cure any secondary diseases, but a
residual population will remain walled up in the macrophages like a ticking
time-bomb just waiting for the fishes immune system to break down so it can
reinfect the rest of the fish.
I have a very large list of references on mycobacteriosis if anyone would
like a copy. I was never able to get a copy of each one but it might be of
some use to anyone who can get access to university reference library exchange??
Here is the information on TB testing:
Piscine mycobacteriosis is a systemic chronic progressive bacterial disease,
which presents varying clinical signs depending on the conditions. The
disease may take several years to develop from an asymptomatic state to
clinical illness. The causative agent Mycobacterium marinum is widespread in
Asian fish farms and is common in imported ornamental fish. It is the most
commonly reported mycobacterial isolate from tropical freshwater and marine
fish. Since 1988 Pemberton Trout hatchery has had sporadic positive tests
for the M. marinum in the kidneys of fish. Attempts to locate the source of
infection are ongoing but are hampered by lack of information on the biology
of the organism, and most especially by the lack of a reliable, cheap and
fast method for detection of the bacterium. The objective of this project is
to develop a PCR based method or detection of the bacterium. PCR methodology
including a list of possible primers for M. marinum have been described. The
test would allow us to screen asymptomatic hatchery fish for the bacterium
so that we could work out how the infections are occurring, and to determine
the prevalence of the bacterium in the fish.
The project would involve: testing primers to determine those that are
specific, testing sensitivity of primers, optimisation of methods for DNA
extraction from blood, culturing of bacteria from blood, screening hatchery
fish. In collaboration with Dr Brian Jones, Ag WA fisheries.
Adrian.
Adrian R. Tappin
Brisbane, Australia.
"Home of the Rainbowfish"
http://www.ecn.net.au/~atappin/home.htm