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by Michael Hornitzky
January 2005
RIRDC Publication No 05/021 RIRDC Project No DAN-219A
Executive summary
American foulbrood (AFB),
caused by Paenibacillus larvae subsp. larvae, is considered to be
the most important bacterial disease of honey bees in Australia. In many
countries oxytetracycline hydrochloride (OTC) is used to treat the disease.
On mainland Australia AFB is controlled by the incineration of infected
hives or the irradiation of hive material from diseased hives. Tasmania
is the only state which permits treatment with OTC.
In recent years OTC-resistant P. l. larvae have emerged in the United States of America, Canada and Argentina. There is no information on the OTC sensitivity of P. l. larvae in Australian bees and whether honey imported from overseas (Argentina) contains OTC-resistant P. l. larvae. This information is important as it has a bearing on future control options for bacterial honey bee diseases in Australia.
This study has demonstrated that P. l. larvae isolated from Australian sources are very sensitive to OTC and that no resistance to OTC appears to have developed over the past 15/16 years. Most isolates from imported honey had higher minimum inhibitory concentrations for OTC than Australian isolates but the difference was so minor that they would all still be considered to be very sensitive to OTC.
This indicates that honey imported from Argentina has not been a significant source of OTC-resistant P. l. larvae.
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