Distribution and variation of Nosema bombi in North American bumble bees

Nils Cordes, Leellen Solter

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Several bumble bee species in North America appear to have undergone rapid declines in abundance. Bombus franklini is potentially extinct; B. occidentalis and B. affinis currently are experiencing extensive range reductions; and a shift in the range of B. pensylvanicus indicates a similar trend. In an unprecedented survey, we collected and evaluated pathogen load in 9,903 specimens of 36 Bombus species in 38 states, but focused on Nosema bombi infections in two putatively declining species, B. occidentalis and B. pensylvanicus, and four stable species. Nosema bombi was recovered from 2.9 % of all collected specimens. It was present in bumble bee populations in 25 of the surveyed states, predominantly in the declining B. occidentalis (37 %) and B. pensylvanicus (15.2 %). N. bombi infections occurred in these two hosts in more than 40 % of surveyed sites, significantly more than for other hosts. Recovered N. bombi isolates were genetically identical to European strains. The only variation in the pathogen among host species was found in the ITS region of the rRNA gene, indicating the presence of multiple alleles. These findings support the hypothesis that N. bombi is Holarctic in distribution, but susceptibility to the pathogen varies among Bombus species.
Original languageEnglish (US)
Title of host publication43rd Annual Meeting of the Society for Invertebrate Pathology and 10th International Colloquium on Invertebrate Pathology, The Final Meeting of COST862 Action: Bacterial Toxins for Insect Control, 11-15 July 2010, Trabzon, Turkey
StatePublished - 2010


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