Cross-infectivity of honey and bumble bee-associated parasites across three bee families.

Lyna Ngor,Quinn S Mcfrederick,Rodrigo Burciaga Nevarez,Sara June Giacomini,Laura Leger,Mario S Pinilla-Gallego,Evan C Palmer-Young,Rebecca E Irwin,Kaleigh A Russell

doi:10.1017/s0031182020001018

Lyna Ngor, Quinn S Mcfrederick + Show 7 more

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https://doi.org/10.1017/s0031182020001018

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Abstract

Recent declines of wild pollinators and infections in honey, bumble and other bee species have raised concerns about pathogen spillover from managed honey and bumble bees to other pollinators. Parasites of honey and bumble bees include trypanosomatids and microsporidia that often exhibit low host specificity, suggesting potential for spillover to co-occurring bees via shared floral resources. However, experimental tests of trypanosomatid and microsporidial cross-infectivity outside of managed honey and bumble bees are scarce. To characterize potential cross-infectivity of honey and bumble bee-associated parasites, we inoculated three trypanosomatids and one microsporidian into five potential hosts - including four managed species - from the apid, halictid and megachilid bee families. We found evidence of cross-infection by the trypanosomatids Crithidia bombi and C. mellificae, with evidence for replication in 3/5 and 3/4 host species, respectively. These include the first reports of experimental C. bombi infection in Megachile rotundata and Osmia lignaria, and C. mellificae infection in O. lignaria and Halictus ligatus. Although inability to control amounts inoculated in O. lignaria and H. ligatus hindered estimates of parasite replication, our findings suggest a broad host range in these trypanosomatids, and underscore the need to quantify disease-mediated threats of managed social bees to sympatric pollinators.

Highlights

Host mobility and interspecific host contact create the potential for transmission of parasites among populations of different hosts
Examples of human-assisted parasite invasions include the spread of the Varroa mite, its associated viruses and the microsporidian Nosema ceranae (Fries et al, 1996) in honey bees (Klee et al, 2007; Rosenkranz et al, 2010) and the spread of the trypanosomatid Crithidia bombi (Lipa and Triggiani, 1988) to South American bumble bees (Arbetman et al, 2012; Schmid-Hempel et al, 2014)
The trial with C. bombi infection of M. rotundata and B. impatiens showed high prevalence of parasite detection in M. rotundata, which was statistically indistinguishable from that achieved in the primary host B. impatiens (Fig. 2)

Summary

Introduction

Host mobility and interspecific host contact create the potential for transmission of parasites among populations of different hosts. The large colonies of social honey bees (Apis spp.) and bumble bees (Bombus spp.) have high potential to spread parasites to other individuals and species by deposition at flowers, which can serve as sites of transmission (Durrer and Schmid-Hempel, 1994; McArt et al, 2014; Graystock et al, 2015; Adler et al, 2018). These circumstances create potential for parasite transfer within plant–pollinator networks, and favour parasites that can exploit multiple hosts. Examples of human-assisted parasite invasions include the spread of the Varroa mite, its associated viruses and the microsporidian Nosema ceranae (Fries et al, 1996) in honey bees (Klee et al, 2007; Rosenkranz et al, 2010) and the spread of the trypanosomatid Crithidia bombi (Lipa and Triggiani, 1988) to South American bumble bees (Arbetman et al, 2012; Schmid-Hempel et al, 2014)

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