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.
Official aide-mémoire (BGD / SSA) – Summary
Aide-mémoire: 2.5 Diarrheal diseases
- Definition: Diarrheal diseases are characterized by fecal traces in and around the hive, accompanied by a general weakening of the colony.
- Possible causes:
- Insufficient quality or fermentation of food reserves.
- Prolonged periods of cold preventing cleansing flights.
- Excessive humidity and poor hive hygiene.
- Presence of pathogens such as Nosema.
- Consequences for the colony:
- Soiling of frames and the interior of the hive.
- Weakening of bees and reduced longevity.
- Disturbed brood development and loss of colony strength.
- Recommended measures:
- Improvement or replacement of food reserves.
- Maintenance of dry and well-ventilated hives.
- Facilitation of cleansing flights when weather conditions permit.
- In case of suspected Nosema, carry out further analyses according to the aide-mémoire.
- Important point:
- A precise analysis of the causes is essential before any targeted intervention.
► Open the official aide-mémoire PDF (FR)
► To the official aide-mémoire page (abeilles.ch)
Note: Section Bee health → 2.5 “Diarrheal diseases”.
Summary established on the basis of aide-mémoire 2.5. Last verification: 01/2026.
See also:
- Review of Nosema parasites in bees
- Principles of bee feeding
- Aide-mémoire: 4.1 Hygiene
- Recognizing bee diseases
