CULTURE OF BACILLUS-LARVAE FROM BULK HONEY SAMPLES FOR THE DETECTION OF AMERICAN FOULBROOD

A method is described for the detection of American foulbrood (AFB) outbreaks, based on the culture of bulk honey samples for Bacillus larvae spores and traceback to hives from which infected honey was extracted. The procedures, which involve the centrifugation of honey, heat treatment of the sediment and culture on to sheep blood agar containing nalidixic acid, also provide an efficient means of locating AFB infection sources where signs of AFB may not be evident. The method was used to examine 505 honey samples (each approximately 125 ml) obtained from 200-litre drums at three packing plants in Australia. B. larvae was identified in 63 samples which had come from 52 of the 315 beekeepers involved. Of these 52, five were aware of the presence of AFB in their colonies, 18 were unaware of its presence, 12 had a history of AFB but were free of it at the time of the investigation, and 17 had neither a recent history of AFB or any colonies showing signs of the disease.