The pathogen Nosema apis is parasitic in epithelial cells in the central part of digestive system of honey bees. The temperature of 60C kills the parasite in 10 minutes and water vapor even for one minute. In the bodies of dead honey bees which suffered this illness parasite can live up to 6 years, the hives and honeycombs can host the parasite up to 2 years and in honey even up to 10 years. The fast spreading of the disease is stopped at temperatures below 10C and above 37C.
The pathogen attacks bees middle intestine where it resides. After being infected bees weaker digest food, and because of so poorly digested food infected honey bee can not during the winter to keep feces and start to defecate inside of hive. Thus, the disease is rapidly expanding and the source of infection are sick and dying bees and their feces spread the hive and on the honey inside of hive. The high fluctuations in outside temperature are very good environmental condition for disease spreading, high humidity in the hives during the winter, late autumn aditional feeding, lack of pollen, long rainy periods, weak spring development community, as well as other diseases that also attack colony at the same time.
Secure diagnosis can be established only by sending a sample to the lab, usually a sample of dead bees (20-30) in March or February. If the disease is in an advanced stage is easily visible even at the hives.
How to cure
Nosema has been widely treated with antibiotics, the most widespread was fumagillin due to its low toxicity to bees, and a good effect on the parasites. However, antibiotics are banned in the EU. The colony can be moved into a new hive, because the disease is not spread by direct contact between bees, while the old hive has to be disinfected and honeycomb melted. In preventing the spread of disease is very important that the bees have access to clean water and good and clean food.
Also there are evidence of two different parasites that cause similar disease with almost the same symptoms, one is above described Nosema apis and another one is Nosema cerane.