Managed bumble bees acquire parasites from their foraging environment: A case study on parasite spillback

Area of Science:

• Ecology
• Pollinator Health
• Disease Ecology

Background:

• Managed bumble bees (Bombus terrestris) in agriculture pose risks to wild pollinators via competition, genetic contamination, and disease transmission.
• Increased parasite prevalence near greenhouses is often attributed to spillover from managed to wild bees.
• Pathogen transmission can also occur from wild to managed bees (spillback), creating a cycle of infection.

Purpose of the Study:

• To investigate the infection routes of parasites in managed bumble bees.
• To assess the role of spillback in parasite dynamics between managed and wild bumble bees.
• To determine the risk of spillback for specific parasites like Apicystis spp., Crithidia spp., and Nosema spp.

Main Methods:

• Field study comparing parasite prevalence and load in managed Bombus terrestris and local wild conspecifics.
• Analysis of infection routes, distinguishing between environmental acquisition and direct transmission.
• Quantification of Apicystis spp., Crithidia spp., and Nosema spp. in managed and wild bumble bee populations.

Main Results:

• Managed Bombus terrestris acquired Apicystis spp. and Crithidia spp. primarily from their foraging environment.
• Managed bees exhibited higher Crithidia prevalence and Apicystis load compared to wild conspecifics.
• Nosema spp. infection route did not appear to be primarily environmental acquisition in managed bees.

Conclusions:

• The foraging environment is a significant infection source for Apicystis spp. and Crithidia spp. in managed bumble bees.
• Spillback, where managed bees are infected by wild pollinators and re-infect them, is a plausible risk scenario for Apicystis and Crithidia.
• Managing parasite loads in managed bees is crucial for mitigating disease spread and protecting both managed and wild pollinator populations.