The impact of Nosema bombi on its bumble bee hosts : ecology, epidemiology and the wider context of multiple parasitism

Abstract

Bumble bees are eusocial insects that play a key role in ecosystem function as essential pollinators for many flowering plants (Alford, 1975). The importance of their diseases, for example damage caused by the microsporidian Nosema bombi, has been recognised since early last century (Fantham & Porter, 1914). Generally, N. bombi could be expected to be a relatively mild disease as the parasite's successful transmission to the next generation and thus its survival depends on the survival of its annual host during the stressful time of hibernation (Bull, 1994; Schmid-Hempel, 1998). However, previous work on this parasite has produced a complex and contradictory picture. While several authors have indeed found few or no externally visible effects of infection, other reports suggest Nosema to be a severe and devastating disease, capable of inhibiting mating, and killing individuals and entire colonies.