Infection of honey bees by Nosema apis has been shown to shorten the lives of worker bees, in part because infected bees begin foraging earlier. Caged bees also have shorter life spans. Infected worker honey bees defecate inside the hives in winter and early spring, transmitting infection to other bees. Infected queens have reduced egg-laying capacity and are superceded more often. At the colony level, Nosema infection causes higher winter mortality and slower spring colony build-up. Honey production is adversely affected in those colonies that do survive through the winter. Some studies have suggested that Nosema ceranae is more virulent than Nosema apis, but most studies have been conducted in the laboratory; no longevity studies have been conducted in the field.

- Zachary Huang, Michigan State University

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