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

Authors: NGOR, LYNA - University Of California; Palmer-Young, Evan; NEVAREZ, RODRIGO - University Of California; RUSSELL, KALEIGH - University Of California; LEGER, LAURA - University Of California; GIACOMINI, SARA JUNE - North Carolina State University; GALLEGO, MARIO - North Carolina State University; IRWIN, REBECCA - North Carolina State University; MCFREDERICK, QUINN - University Of California

Submitted to: Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/11/2020
Publication Date: 6/18/2020
Citation: Ngor, L., Palmer-Young, E.C., Nevarez, R.B., Russell, K.A., Leger, L., Giacomini, S., Gallego, M.P., Irwin, R.E., Mcfrederick, Q.S. 2020. Cross-infectivity of honey and bumble bee-associated parasites across three bee families. Parasitology. https://doi.org/10.1017/S0031182020001018.
DOI: https://doi.org/10.1017/S0031182020001018

Interpretive Summary: Parasites associated with honey and bumble bees have been detected in field samples of other bee species, but experimental tests of infectivity are lacking. We tested the infectivity of four parasites (three trypanosomatids and one microsporidian) in five host species of bees from three taxonomic families. Experimental infection with the bumble bee-associated trypanosomatid Crithidia bombi was established in the ligated furrow bee Halictus ligatus, the blue orchard bee Osmia lignaria, and the alfalfa leafcutter bee Megachile rotundata. Infection with the honey bee-associated trypanosomatid Crithidia mellificae was established in both Halictus ligatus and Osmia lignaria. In many cases, infections were more successful in these novel hosts than in the known host. Our results underscore the potential for parasites of managed bees to afflict co-occurring, phylogenetically diverse pollinators.

Technical Abstract: Recent declines of wild pollinators and detection of infectious diseases in honey, bumble, and other bee species have raised concerns about potential 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, which suggests the potential for spillover to co-occurring species via shared floral resources. However, controlled experiments that test the infectivity of trypanosomatids and microsporidia outside of managed honey and bumble bees are scarce. To characterize the potential for spread of honey- and bumble bee-associated microsporidia and trypanosomatids among bee species, we tested infectivity of three trypanosomatids and one microsporidian in five species of bees from three taxonomic families. We found high levels of cross-infection by the trypanosomatids Crithidia bombi and Crithidia mellificae, which established in a combined 7 of 9 hosts. These include the first reports of experimental C. bombi infection in Megachile rotundata, and of both C. bombi and C. mellificae in Osmia lignaria and Halictus ligatus. Our findings expand the known host range of these trypanosomatids and underscore the need to quantify disease-mediated threats of managed social bees to agriculturally important and threatened pollinators.