Study of Nosema spp. In the Tomsk region, Siberia: Co-infection is widespread in honeybee colonies

Abstract

Microsporidian protozoans Nosema are gut parasites that infect European honeybees (Apis mellifera) worldwide. In the Tomsk region, two species of microsporidia were registered in honeybees (A. mellifera): N. apis and N. ceranae. During the last 6 years, an increase in infections by Nosema in honeybees has been detected in the Tomsk region, while cases of mass bee colony deaths were rare (in 2016, two cases of winter losses of bee colonies in the northern districts of the Tomsk region have been reported by beekeepers). The infestation of bee colonies and apiaries have changed from 0% in 2012 to about 80% in 2016-2017. In 2013-2014, 60.0% of all infected apiaries were infected only with N. apis. In 2015-2017, most of the infected apiaries (52.2%) were infected with both species of microsporidia. Despite the predominance of co-infection in honeybees, replacement of N. apis by N. ceranae is not observed.