Pébrine is a disease of silkworms, which is caused by microsporidian parasites, mainly Nosema bombycis and to a lesser extent Variomorpha, Pleistophora and Thelophania species.
The silkworm larvae infected by pébrine are usually covered in brown dots and are unable to spin silkworm thread. Louis Pasteur was the first one to recognize the cause of this disease when the plague of the disease was spread in France.
Nosema bombycis (Pébrine) is a microsporidium that kills 100% silkworms hatched from infected eggs. Nosema bombycis is a microsporidium that can be carried over from worms to moths then eggs and worms again. This microsporidium comes from the food that silkworms eat. If silkworms get this microsporidium in their larva stage, there are no visible symptoms. However, mother moths will pass the microsporidium onto the eggs, and 100% of worms hatching from the infected eggs will die in their larva stage. Therefore, it is extremely important to rule out all eggs from infected moths by checking the moth’s body fluid under a microscope.