Nosema ceranae, a new threat to honey bees (Apis mellifera L.)?

Back in 1900 already, the Mikrosporidium Nosema apis was described in Apis inellifera. Thereby the Nosemosis remains without symptoms in the beehive to a certain degree. Studies indicate that infected bees have a shortened life span, due to a series of changes in physiological parameters. The consequence of these changes are diarrheal symptoms and the spread of infectious spores in the hive. There is also a seasonal infection course observed, which has its peak in spring time (April, May). Colloquially, the Nosemosis is therefore also known as spring shrinking craze. More recently, a new Nosema species in the European honey bee has been described, where a host-switch from the Asian honey bee A. cerana to A. mellifera has occurred. N. ceranae is blamed for colony losses in the south of Spain, many general colony losses during wintertime in Europe and has also a contribution to the Colony Collapse Disorder (CCD) in the U.S. It seems likely that the original Nosema species (N. apis) is displaced more and more by N. ceranae for unknown reasons. Within the EU project BEE DOC", monitoring studies on colonies in southern Germany, Switzerland, southern France, Sweden and Finland were performed. Although the high prevalence of N. cemnae could be confirmed, no increased colony mortality due to Nosemosis was recorded. This was also observed by other colleagues and thus the new threat" is open to debate.