from APIS Volume 18, Number 1, January 2000 :

Mr. Laurence Cutts of the Division of Plant Industry's Apiary Bureau
(Florida) is burning more colonies that have become symptomatic than
in past years. Many of these have been treated with antibiotic
apparently to little avail. Tests at both the Florida and Federal
Beekeeping Laboratory in Beltsville, Maryland have confirmed what
appears to be a growing tolerance by the causative organism
(Paenibacillus larvae larvae) for the only currently labeled
antibiotic, Terramycin. This should be no surprise. It parallels what
is happening in other livestock industries, as well as humans,
signaling that the era of antibiotics as a wonder drug may be drawing
to a close.

The good news is that Dr. H. Shimanuki of the Beltsville Bee
Laboratory sees a new era dawning such that we can expect to see
advances made in the materials and methods available for detection,
prevention and control of AFB. The bad news is that this may take
some time, and those beekeepers having the problem now could be
ill-equipped to deal with it. One of the reasons for this is that
many are not familiar with the disease's etiology and detection.
These have taken low priority in the face of 40 years of effective
masking by Terramycin.

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The bee law in Pennsylvania allows for treatment of diseased colonies
at the discretion of the inspector. An inspector who finds AFB will
evaluate the situation and explain all the possible alternatives to
the beekeeper, who will then decide how to treat the disease. If the
colony is weak or heavily infested, the only alternative is to kill
the bees and burn the frames and combs. If the disease is diagnosed
in its early stages and the colony is strong, it may be treated with
terramycin. A diseased colony treated with terramycin should be
considered contaminated with spores forever and should be treated
preventatively with terramycin indefinitely. A colony is not cleansed
of AFB after treating for a year, 2 years or even 5 years. If a
colony has had AFB and the terramycin treatment is discontinued the
disease will come back.

Terramycin (oxytetracycline) is the only drug approved for use
against American Foul Brood. When present in the food given to
susceptible larvae this antibiotic is effective in preventing
germination of AFB spores. The bees are then able to develop and
mature normally. Terramycin will not kill the spores and is not a
means for sterilizing either the bees or the equipment. If a colony
contains AFB spores and is maintained in a healthy condition through
treatment with terramycin, the disease will recur when the drug
treatment is discontinued.

http://sites.state.pa.us/PA_Exec/Agriculture/bureaus/plant_industry/apiary/apiary_pests.html

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AFB is regulated by the Georgia Department of Agriculture, and
infected colonies are normally burned by state inspectors. As state
budgets allow, beekeepers may be indemnified for these losses. The
spores of the AFB bacterium are extremely persistent in contaminated
comb and hive parts. Although resistant bee colonies may clean up
visible signs of infestation, it is more typical for AFB to be
incurable and essentially doom the colony. Beekeepers should never
maintain hospital yards in which they group AFB colonies together in
isolation. Such yards simply serve as reservoirs of disease that will
serve to contaminate apiaries for miles around. It is equally
inadvisable to treat infected colonies with Terramycin. The
antibiotic will simply obscure visible signs of the disease, but the
symptoms will rapidly recur once the antibiotic is removed.

http://www.ent.uga.edu/bees/Disorders/American_Foulbrood.htm

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--
Peter Borst <[log in to unmask]>