2.5 Diarrhoeal diseases

Diarrhoea in bees is most often caused by Nosema or dysentery. Nosema is a fungal disease that can be caused by two different pathogens: Nosema apis and Nosema ceranae. Transmission occurs in the form of spores via food, water, and contaminated surfaces. The fungus germinates in the midgut and subsequently multiplies in the intestinal cells. New spores are transmitted through the excreta. In this factsheet, only diarrhoea resulting from Nosema apis is addressed and discussed. The disease is strongly season-dependent and occurs mainly in spring. The pathogen can be detected within the colony throughout the year even in the absence of clinical symptoms.