Mathematical models for the study of the transmission of Nosema ceranae through a honey bee colony (Apis mellifera)

Abstract

For the past decade global honey bee (Apis mellifera) colony losses have been above the average trend, while the benefit of honey bee pollination to worldwide agriculture is increasingly recognised. Honey bees are the primary pollinator for many food crops, leading to concern about agricultural productivity and world food security. This thesis examines the effects of the disease Nosema ceranae on a honey bee colony's health and longevity, and how it can work in conjunction with other factors to cause the rapid depopulation of a hive. Three models are presented which explore different methods of simulating colony failure events. Two differential equation models with a susceptible-infected (SI) structure show that the interaction of infection with a colony's social dynamics can create detrimental imbalances in the population structure. In particular modelling food and an age parameter for the colony's foragers is vital for simulating rapid colony failures during summertime. The model suggests that the level of N. ceranae infection is sensitive to the health of the colony's foragers. In simulations a moderate increase in the mortality rate of the foragers can slow the transmission of the disease within the hive. The third simulation model, a discrete model, expands on the analysis of the colony's social structure by including a full age distribution for the colony. Low food and young foragers create a feedback loop that causes the abandonment of the hive by the majority of the adult bees and a colony collapse. The model also suggests that N. ceranae infections are driven by infected hive bees aged around 10 days old.