Microscopic and molecular detection of Nosema ceranae in honeybee Apis mellifera L. from Romania: Status on pathogen worldwide distribution

Until now, in Romania, a country in southeastern Europe located on the Balkans Peninsula, information regarding the status on A. mellifera honey bee infection by Nosema spp. has not been published. The aims of the present study were to survey the occurrence and identification of Nosema spp. in A. mellifera honeybee
colonies from 37 apiaries located in Arad, Caras-Severin and Timis Counties, Romania. Also, based on published literature an update on the distribution of N. ceranae infection among A. mellifera colonies worldwide was performed. Overall, a frequency of 55.1% (389/690) of Nosema infection was observed in
the analyzed regions (ranging from 52% to 66%), by light microscopy. By PCR and DNA sequencing, N. ceranae was the only microsporidia identified. Nosema ceranae is clearly a novel, emergent pathogen of A.mellifera with potentially very serious effects on the individual and honeybee’s colonies in Romania. Data
obtained provide new and important information on N. ceranae geographic prevalence and distribution, and on its impact at colony level and/or its role in colony losses. The present study intends to contribute to highlight the importance of implementing prevention, treatment and control measures of honeybee nosemosis, in Romania.