AUTHOR=Gisder Sebastian , Schüler Vivian , Horchler Lennart L. , Groth Detlef , Genersch Elke 

TITLE=Long-Term Temporal Trends of Nosema spp. Infection Prevalence in Northeast Germany: Continuous Spread of Nosema ceranae, an Emerging Pathogen of Honey Bees (Apis mellifera), but No General Replacement of Nosema apis

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=7

YEAR=2017

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2017.00301

DOI=10.3389/fcimb.2017.00301

ISSN=2235-2988

ABSTRACT=<p>The Western honey bee (<italic>Apis mellifera</italic>) is widely used as commercial pollinator in worldwide agriculture and, therefore, plays an important role in global food security. Among the parasites and pathogens threatening health and survival of honey bees are two species of microsporidia, <italic>Nosema apis</italic> and <italic>Nosema ceranae. Nosema ceranae</italic> is considered an emerging pathogen of the Western honey bee. Reports on the spread of <italic>N. ceranae</italic> suggested that this presumably highly virulent species is replacing its more benign congener <italic>N. apis</italic> in the global <italic>A. mellifera</italic> population. We here present a 12 year longitudinal cohort study on the prevalence of <italic>N. apis</italic> and <italic>N. ceranae</italic> in Northeast Germany. Between 2005 and 2016, a cohort of about 230 honey bee colonies originating from 23 apiaries was sampled twice a year (spring and autumn) resulting in a total of 5,600 bee samples which were subjected to microscopic and molecular analysis for determining the presence of infections with <italic>N. apis</italic> or/and <italic>N. ceranae</italic>. Throughout the entire study period, both <italic>N. apis</italic>- and <italic>N. ceranae</italic>-infections could be diagnosed within the cohort. Logistic regression analysis of the prevalence data demonstrated a significant increase of <italic>N. ceranae</italic>-infections over the last 12 years, both in autumn (reflecting the development during the summer) and in spring (reflecting the development over winter) samples. Cell culture experiments confirmed that <italic>N. ceranae</italic> has a higher proliferative potential than <italic>N. apis</italic> at 27° and 33°C potentially explaining the increase in <italic>N. ceranae</italic> prevalence during summer. In autumn, characterized by generally low infection prevalence, this increase was accompanied by a significant decrease in <italic>N. apis</italic>-infection prevalence. In contrast, in spring, the season with a higher prevalence of infection, no significant decrease of <italic>N. apis</italic> infections despite a significant increase in <italic>N. ceranae</italic> infections could be observed. Therefore, our data do not support a general advantage of <italic>N. ceranae</italic> over <italic>N. apis</italic> and an overall replacement of <italic>N. apis</italic> by <italic>N. ceranae</italic> in the studied honey bee population.</p>