Effects of Invasive Parasites on Bumble Bee Declines

Abstract

Bumble bees are a group of pollinators that are both ecologically and economically important and declining worldwide. Numerous mechanisms could be behind this decline, and the spread of parasites from commercial colonies into wild populations has been implicated recently in North America. Commercial breeding may lead to declines because commercial colonies may have high parasite loads, which can lead to colonization of native bumble bee populations; commercial rearing may allow higher parasite virulence to evolve; and global movement of commercial colonies may disrupt spatial patterns in local adaptation between hosts and parasites. We assessed parasite virulence, transmission mode, and infectivity. Microparasites and so-called honey bee viruses may pose the greatest threat to native bumble bee populations because certain risk factors are present; for example, the probability of horizontal transmission of the trypanosome parasite Crithidia bombi is high. The microsporidian parasite Nosema bombi may play a role in declines of bumble bees in the United States. Preliminary indications that C. bombi and the neogregarine Apicystis bombi may not be native in parts of South America. We suggest that the development of molecular screening protocols, thorough sanitation efforts, and cooperation among nongovernmental organizations, governments, and commercial breeders might immediately mitigate these threats.

A sting in the spit: widespread cross‐infection of multipleRNAviruses across wild and managed bees

“…2011; Meeus et al . 2011). First, the direction of disease spillover between managed and wild bees represents a major unanswered question.…”

Chronic neonicotinoid pesticide exposure and parasite stress differentially affects learning in honeybees and bumblebees

“…[17,18]). This is of major concern given that, due to anthropogenic influence, both wild and managed bees are increasingly exposed to sub-lethal concentrations of neonicotinoids [19], and emerging pathogens and parasites [20][21][22]. However, the potential interactive effects of neonicotinoids and parasites, such as the emergent microsporidian parasite Nosema ceranae [23], on associative learning in bees has received little attention.…”

Parasites in bloom: flowers aid dispersal and transmission of pollinator parasites within and between bee species

“…There is currently great interest in the stress factors affecting pollinators, many of which are showing substantial population declines with knock-on effects on the plants that rely on them for pollination [17][18][19]. Parasites are well established as being an important factor in at least some of these declines, with several bumblebee species showing population declines that correlate with pathogen spillover from commercially produced bumblebees [20][21][22][23][24][25][26][27][28], and honeybee colony losses in many countries being associated with emerging parasites such as the Varroa mite and the microsporidian Nosema ceranae [29][30][31][32][33][34]. Importantly, there is increasing evidence of parasite transmission between pollinator taxa being more significant than has generally been appreciated.…”