Chalkbrood is a fungal (mycotic) disease of honeybee larvae caused by Ascosphaera apis (A. apis) with no effective treatment available. During the ‘90’s the Kimron Veterinary Institute, the Tierhygienisches Institute and the Bee Keeping Centre at Chiang Mai collaborated in a project to attempt the control of A. apis infestation by biological methods. Vita (Europe) Limited has been collaborating further on this project, extending the field trials and working towards bringing a product to market.
Chalkbrood is a mycotic disease of the honeybee larva caused by A. apis. It has been reported that the susceptibility of colonies to the fungus varies considerably. Consequently, the level of infestation is probably a result of the pathogenicity of the fungus, the vitality of the colony and the environmental factors. It is likely that a strong colony will be able to limit the level of infestation by efficiently eliminating the infected larvae from the hive. If, however, the infestation exceeds a certain level it is possible that a vicious circle will initiate: The weakened colony is unable to eliminate the infected larvae which increases the infestation level leading to a further weakening of the colony. Under such circumstances an intervention in favour of the host might reverse this vicious circle and the balance between the fungus and the bees might be re-established by a newly invigorated colony. Consequently, the total elimination of A. apis from the hive might not be necessary. The microorganism used to control A. apis must be non pathogenic for the bee colony and healthy larvae were screened and a micro organism was isolated and identified as a Bacillus sp. In-vitro the activity of the Bacillus sp. was found to be fungi static. The in-vivo implication of this finding is that by limiting the hive’s infestation by the fungus (without eliminating it), the colony will strengthen and the balance between the pathogen and the host will be re-established. Various factors might contribute to the disruption of the natural balance between the components of the hive’s micro flora but the extensive use of antibacterial drugs is probably one of the most important ones. The fact that the Bacillus sp. Isolated and used by us is susceptible to two of the most widely used antibiotic drugs (streptomycin and tetracycline) strengthens the contention that higher levels of chalkbrood infestation are connected to an altered microbial balance. Consequently, restoring this balance (even partially) should contribute to the reduction of A. apis infestation levels. In-vivo experiments in all countries indicate a significant decrease in A. apis infestation following treatment with the Bacillus sp., thus confirming the in-vitro findings and establishing that the biological control of chalkbrood (by the use of Bacillus sp.) was feasible. Vita (Europe) Limited have instigated further in-vivo trials notably in Spain, Italy and Greece to add to the data already gathered from trials in Israel, Germany, Switzerland and Thailand. Vita (Europe) Limited is looking to bring a product to the world market in 2005.
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