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Government Of Assam Handloom Textiles & Sericulture Directorate of Sericulture

Diseases of Silkworm

Protozoan disease (Pebrine) of Muga silkworm

Muga silkworm suffers heavily from pebrine. The pebrine disease is locally known as phootuka “Saiutha” (spotted) in Assamese and is caused by the protozoan parasite Nosema bombycis (Nosema sp.) of the family Nosematidae. Nosema parasite invades all the tissues of the body of the embryo, larva, pupa and moth. The disease is mechanically inherited to the off- springs from infected mother moth through the eggs. If no steps are taken to detect and isolate the diseased worms, an epidemic starts and infects all the host- larvae and the disease is carried to the next generation through the ova. This process of germinative infection through the reproductive organs of the host was established by Louis Posteur as early as 1870.

There are two stages in its life cycle i.e. the spore stage and the vegetative stage. he life cycle of Nosema sp. is completed in a week after infection in winter and four days in summer. The examination of moths is most essential. Examination of mother moths is the only procedure to control of this disease. Healthy larvae at fourth and fifth are also susceptible to pebrine due to seconday contamination, in such case depending on the stage and severity of the infection the muga silkworm growth is affected. After examination the disease free eggs should be treated in 2% formaline for 5 minutes to kill the germs of pebrine. Disinfection of tools and appliances of the rearing house by 2% formaline is essentially necessary to control the pebrine disease. But the measures cannot be applied in case of outdoor of the disease can be minimized except local occurrence. It is also inferred that pebrine protozoon of muga silkworm looses its viability after about six months.