Five-Year Cohort Study of Nosema spp. in Germany: Does Climate Shape Virulence and Assertiveness of Nosema ceranae ?

Abstract

Nosema ceranae and Nosema apis are two fungal pathogens belonging to the phylum Microsporidia and infecting the European honeybee, Apis mellifera. Recent studies have suggested that N. ceranae is more virulent than N. apis both at the individual insect level and at the colony level. Severe colony losses could be attributed to N. ceranae infections, and an unusual form of nosemosis is caused by this pathogen. In the present study, data from a 5-year cohort study of the prevalence of Nosema spp. in Germany, involving about 220 honeybee colonies and a total of 1,997 samples collected from these colonies each spring and autumn and analyzed via species-specific PCR-restriction fragment length polymorphism (RFLP), are described. Statistical analysis of the data revealed no relation between colony mortality and detectable levels of infection with N. ceranae or N. apis. In addition, N. apis is still more prevalent than N. ceranae in the cohort of the German bee population that was analyzed. A possible explanation for these findings could be the marked decrease in spore germination that was observed after even a short exposure to low temperatures (؉4°C) for N. ceranae only. Reduced or inhibited N. ceranae spore germination at low temperatures should hamper the infectivity and spread of this pathogen in climatic regions characterized by a rather cold winter season.

Occurrence of parasites and pathogens in honey bee colonies used in a European genotype-environment interactions experiment

“…Comparatively few reports describe mite levels considered responsible for colony damage or death from different environments (Delaplane and Hood, 1999;Strange and Sheppard, 2001;Currie and Gatien, 2006;Büchler et al, 2010;Carreck et al, 2010;Genersch et al, 2010). The results presented here indicate that threshold levels for colony damage and death are very likely to differ substantially across Europe.…”

“…With a few exceptions in single countries (Topolska et al, 2009;Genersch et al, 2010), there are no recent comprehensive compilations of honey bee pathogen presence in Europe. However, the currently ongoing pilot surveillance project on honey bee colony losses, coordinated by the European Reference laboratory for honey bee diseases, may provide an improved view in due course (Chauzat et al, 2013a(Chauzat et al, , 2013b.…”

“…The autumn samples (taken in September or October, depending on location) of 2010 were analysed for the honey bee viruses APBV and DWV, known to be relevant for winter losses (Genersch et al, 2010;Francis et al, 2013a). Analogous to the procedure described in Genersch et al (2010), total RNA was extracted from the heads of ten bees using standard methods (Yue et al, 2006;de Miranda et al, 2013).…”

“…Analogous to the procedure described in Genersch et al (2010), total RNA was extracted from the heads of ten bees using standard methods (Yue et al, 2006;de Miranda et al, 2013).…”

“…Fuelled by the recent and ongoing debate on worldwide honey bee decline and elevated colony losses, the role of pathogens has received intensive scientific attention in recent years (Tentcheva et al, 2004;Chen et al, 2006;Berthoud et al, 2010;Genersch et al, 2010;Vejsnaes et al, 2010;Antunez et al, 2012;Dainat et al, 2012), providing a wealth of information on key pathogens linked to winter losses, but also to phenomena such as "Colony Collapse Disorder" (CCD) (Cox-Foster et al, 2007;Cornman et al, 2012;Nazzi et al, 2012).…”