Nosema apis and Nosema ceranae are microsporidial species belonging to the kingdom of Protista. Both species cause nosemosis, an infectious disease in bees. Nosemosis causes significant economic losses each year due to lowering productivity of bee colonies.
Both Nosema apis and Nosema ceranae reproduce in the epithelial cells of the small intestine of bees. Cells filled with spores are destroyed, which causes, inter alia, impairment of digestion and food absorption. Weakened families cannot produce milk and are susceptible to bacterial, viral and fungal diseases. Nosemosis caused by N. apis is usually chronic and is characterized by seasonal intensity during the wintering season of the colonies. When infected with N. ceranae diseased bees die within 8-10 days after infection. Currently, in Poland, the greatest threat to apiaries is Nosema ceranae, which has better adapted to climatic conditions and can develop throughout the year.