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Published on: October 9, 2017
Antimicrobial control and temporal dynamics of M. plutonius colonization in adult worker honey bees (Apis mellifera)
Midhun Sebastian Jose1, Marina Carla Bezerra da Silva1, Oleksii Obshta1
1Department of Veterinary Pathology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
Abstract:
European foulbrood (EFB) is a stress-associated brood disease affecting honey bee larvae, caused by infection with Melissococcus plutonius. Adult bees are suggested to be a reservoir for this bacterium; however, the duration of M. plutonius colonization of adult bees and its impact on adult bee survival remain inadequately understood. In North America, the only approved antimicrobial for treatment of EFB is oxytetracycline; yet the antimicrobials tylosin and lincomycin are also widely used in beekeeping. The effect of these antimicrobials on M. plutonius colonization of adult bees is unclear. To investigate these unknowns, we infected summer and winter adult worker bees with M. plutonius in the laboratory and treated the infected workers with one of three used antibiotics in beekeeping, in either the laboratory, or within field colonies. We found that worker bees remained persistently infected with M. plutonius for at least 22-38 days in the laboratory and at least 24 days in field colonies. Moreover, M. plutonius ingestion was associated with a significant, dose-dependent decrease in adult worker survival. Antibiotic treatment significantly decreased the M. plutonius load of colonized adult workers but failed to eliminate M. plutonius; still antibiotic treatment improved the survival of bees in the laboratory cages. Taken together, these findings indicate the importance of adult bees as a reservoir of M. plutonius, even in colonies treated with antimicrobials.
Insights
Adult honey bees can carry European foulbrood (EFB) bacteria, Melissococcus plutonius, for weeks, impacting survival. Antibiotics reduce bacterial load but do not eliminate it, highlighting adult bees as a persistent reservoir.
Area of Science:
- Apiculture
- Insect Pathology
- Microbiology
Background:
- European foulbrood (EFB) is a significant honey bee larval disease caused by Melissococcus plutonius.
- Adult bees are suspected reservoirs for M. plutonius, but colonization duration and survival impact are poorly understood.
- Commonly used antimicrobials like oxytetracycline, tylosin, and lincomycin have unclear effects on M. plutonius in adult bees.
Purpose of the Study:
- To determine the duration of Melissococcus plutonius colonization in adult worker bees.
- To assess the impact of M. plutonius infection on adult bee survival.
- To evaluate the efficacy of common beekeeping antimicrobials against M. plutonius in adult bees.
Main Methods:
- Adult worker bees (summer and winter) were experimentally infected with M. plutonius.
- Infected bees were treated with oxytetracycline, tylosin, or lincomycin in laboratory and field settings.
- Bacterial load and adult bee survival were monitored over time.
Main Results:
- Persistent M. plutonius colonization in adult bees lasted at least 22-38 days (lab) and 24 days (field).
- M. plutonius infection led to a dose-dependent decrease in adult worker bee survival.
- Antimicrobial treatments reduced M. plutonius loads but did not eradicate the bacteria, though they improved survival in lab conditions.
Conclusions:
- Adult bees serve as a crucial reservoir for M. plutonius, persisting even in antimicrobial-treated colonies.
- The limited efficacy of current antimicrobials against adult bee colonization underscores the need for integrated pest management strategies.
- Understanding adult bee reservoir dynamics is vital for controlling European foulbrood disease in honey bee populations.
