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Title: Infectivity and virulence of Nosema ceranae and Nosema apis in commercially available North American honey bees

Author
item HUANG, WEI-FONE - Illinois Natural History Survey
item SOLTER, LEELLEN - Illinois Natural History Survey
item Aronstein, Katherine
item HUANG, ZACHARY - Michigan State University

Submitted to: Journal of Invertebrate Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/15/2015
Publication Date: 1/15/2015
Citation: Huang, W., Solter, L., Aronstein, K.A., Huang, Z. 2015. Infectivity and virulence of Nosema ceranae and Nosema apis in commercially available North American honey bees. Journal of Invertebrate Pathology. 124:107-113.

Interpretive Summary: Nationwide displacement of N. apis suggests that N. ceranae may have competitive advantages over N. apis. Our studies, however, showed that N. ceranae was significantly less infective and less virulent than N. apis in the commercially available lineages of honey bees we used. Experiments were conducted in both Illinois and Texas. Honey bees were most susceptible to infection by both Nosema species at 5 days post eclosion. N. ceranae was less infective in these US studies than those using European strains of honey bees, both in Europe and in Canada. N. apis infectivity, however, tested in the same cohort of honey bees as N. ceranae, was similar to results reported globally from 1972-2010. At a dosage of 50 spores, mortality of worker bees was similar for N. apis and N. ceranae infected bees and for control bees. At dosages of = 500 spores, mortality was significantly higher for N. apis. Comparing the results of our two US laboratories and from two other US studies, all of which used mixed lineages of honey bees, we suggest that either US honey bees are less susceptible to N. ceranae infections than European bees or that the US isolates of the pathogen are less infective and less virulent than European isolates.

Technical Abstract: Nosema ceranae infection is ubiquitous in western honey bees, Apis mellifera. In the US, displacement of N. apis in bee colonies suggests that N. ceranae has competitive advantages. Our study, however, showed that N. ceranae was significantly less infective and less virulent than N. apis in commercially available lineages of honey bees in studies conducted in Illinois and Texas. Mortality of worker bees was similar for both pathogens at a dosage of 50 spores and not different from the uninfected controls, but was significantly higher for N. apis than N. ceranae at dosages = 500 spores. N. apis was also more infective than N. ceranae. At 5 days post eclosion, the most susceptible age of adult bees tested, the mean ID50 (dosage infecting 50% of treated bees) for N. apis was 359 spores compared to 3,217 N. ceranae spores, a nearly 9-fold difference. Infectivity of N. ceranae was also significantly lower than N. apis for 24-hour and 14-day worker bees. N. ceranae was less infective than reported in studies using European strains of honey bees, while N. apis infectivity, tested in the same cohort of honey bees, corresponded to results reported globally from 1972-2010. Our results provide comparisons for evaluating research using different ages of bees and pathogen dosages and clarify some controversies. In addition, comparisons among studies suggest that the mixed lineages of US honey bees may be less susceptible to N. ceranae infections than are European bees or that the US isolates of the pathogen are less infective and less virulent than European isolates.