A contribution to the knowledge of Nosema infections in bumble bees, Bombus spp

Abstract - Experimental infections of adult and larval workers and adult males of Bombus terrestris with the microsporidium Nosema bombi showed all stages and both sexes to be susceptible. On average 19-29 % of infections were successful and no significant differences among these host categories were found. Different sources of Nosema spores differed in their success in infecting different host colonies, suggesting genotype-genotype interactions at the level of colonies and parasite sources. In a second experiment, N. bombi obtained from B. terrestris were found to be infective for workers of B. lapidarius and B. hypnorum, although less so in these foreign hosts. On the other hand, case mortality was significantly higher in foreign hosts than in B. terrestris. Infection and high spore loads correlated with early death of the host. In addition, a factorial analysis showed that variation among-colonies-within-species explained more of the variation in infection success than the factor species per se. © Inra/DIB/AGIB/Elsevier, Paris