American foulbrood (AFB) is a disease of larval honey bees caused by the spore-forming bacterium, Paenibacillus larvae larvae. Strains of this pathogen resistant to oxytetracyline, the only registered antibiotic for use against this disease, are now present in most U.S. states and in western Canada. Antibiotic-resistant AFB poses a serious threat to the beekeeping industry in North America and has caused serious losses to producers, who have few management tools available to them. Our objective was to develop a predictive relationship between the numbers of P. larvae larvae spores found in colonies and the clinical incidence and severity of AFB. In the spring of 2002, 40 imported colonies of Apis mellifera were established on woodenware and comb that was treated with electron beam irradiation to destroy any viable AFB spores present. After colonies had progressed through several brood cycles, they were placed in 5 isolated apiary sites and inoculated with a range of doses of spores (0 to 108 spores/ colony) by aspirating a type strain of AFB onto two - 100 cm2 patches of L1 larvae. Colonies were inspected weekly for the development of AFB clinical symptoms, and spore samples were taken from adult bees, honey, and swabs from within the hives. Spores were enumerated by evaluating colony growth on diagnostic media, and susceptible and resistant strains were identified using an antibiotic disk diffusion assay. The relationship between AFB spore levels and disease epidemiology will be discussed in concert with other management tools being developed for this disease in Canada.
Species 1: Hymenoptera Apidae Apis mellifera (honey bee)
Keywords: honey bees, AFB disease
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