The spores are ingested with food and germinate in the bee’s mid-gut. The pathogens released infest the cells of the intestinal wall where they begin to multiply. The host cells are destroyed at the end of the reproductive cycle and the spores (dormant phases of the pathogen) are released into the gut. Now, the spores germinate once more and infect new cells or they are discharged with the bee’s faeces. Spores in bee faeces remain contagious for over one year. Worker bees, drones and queens can suffer from such an infection.
Nosema apis: seasonal occurrence, peak levels in spring and autumn, typical symptoms are a decline in the bee population, reduction of bee mass, bee faeces that are liquid, faeces spots on combs and the landing board, many dead bees, crawling bees that are unable to fly.
Nosema ceranae: occurs throughout the year, colonies are destroyed, there are declines in the bee population, few to no dead bees in the hive (pollen collectors die some distance away from the hive), and there is reduced honey production, an unexpected increase in bee reproduction in cold months, and there are noticeable numbers of crawling bees that are unable to fly.
The disease is transmitted either from colony to colony (robbery, bees landing at the wrong hive, watering stations contaminated with faeces) or via the beekeeper (changing or adding of contaminated combs, putting weak or infected colonies together with healthy colonies, equipment and boxes contaminated with spores, feeding supplies from Nosema-contaminated colonies).
Choose a suitable location, hygiene measures, timely and sufficient food for the winter, adjust to the colony’s life cycle and the honey flow situation.
There are no approved control agents available to combat the two Nosema pathogens in Austria.