A model of infection in honeybee colonies with social immunity

PLoS One. 2021 Feb 22;16(2):e0247294. doi: 10.1371/journal.pone.0247294. eCollection 2021.

Abstract

Honeybees (Apis mellifera) play a significant role in the pollination of various food crops and plants. In the past decades, honeybee management has been challenged with increased pathogen and environmental pressure associating with increased beekeeping costs, having a marked economic impact on the beekeeping industry. Pathogens have been identified as a contributing cause of colony losses. Evidence suggested a possible route of pathogen transmission among bees via oral-oral contacts through trophallaxis. Here we propose a model that describes the transmission of an infection within a colony when bee members engage in the trophallactic activity to distribute nectar. In addition, we examine two important features of social immunity, defined as collective disease defenses organized by honeybee society. First, our model considers the social segregation of worker bees. The segregation limits foragers, which are highly exposed to pathogens during foraging outside the nest, from interacting with bees residing in the inner parts of the nest. Second, our model includes a hygienic response, by which healthy nurse bees exterminate infected bees to mitigate horizontal transmission of the infection to other bee members. We propose that the social segregation forms the first line of defense in reducing the uptake of pathogens into the colony. If the first line of defense fails, the hygienic behavior provides a second mechanism in preventing disease spread. Our study identifies the rate of egg-laying as a critical factor in maintaining the colony's health against an infection. We propose that winter conditions which cease or reduce the egg-laying activity combined with an infection in early spring can compromise the social immunity defenses and potentially cause colony losses.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Beekeeping / methods
  • Bees / physiology*
  • Behavior, Animal / physiology*
  • Feeding Behavior / physiology
  • Plant Nectar
  • Pollination / physiology
  • Social Behavior

Substances

  • Plant Nectar

Grants and funding

T.L. and O.D. acknowledge the Thailand Research Fund (TRF) and King Mongkut’s University of Technology Thonburi (KMUTT) under Contract Number MRG5980039 for providing the financial supports. TRF had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. KMUTT provided support in the form of salaries for authors [T.L., T.T., A.T., and O.D.], but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the ‘author contributions’ section.