it is protozoal silkworm disease , it is only disease spread througt parent material also.

2. Pebrine

3. Pebrine
Pebrine is the most serious disease in silkworms as it is highly infectious and
infects the silkworm larvae causing considerable loss.
Causative agent : Nosema bombycis different strains of microsporidia.
Occurrence/observed : Rainy and winter season.

4. Source of infection
Primary infection
Transmitted from the infected mother to the offspring by transovarial.
Secondary infections during
Early 4th larval stages flimsy cocoon.
5th larval stages well formed cocoons.
Spreading of spores through the faecal matter and infected larvae.

5. Stages of infection
A) Through eggs (transovarian/transovum transmission).
B) By eating contaminated mulberry leaf(per oral).
1. Initial stage of infection:
 infected larvae appear to be healthy.
 Only microscopic examination of the silkworm larvae may indicate the
presence of shinning spore of Nosema.

6. 2. Advanced stage of infection:
 Loose appetite, unequal in size,retard in growth, moult
Irregularly.
 The dead larvae turn black in colour.
 If infection is at late 4th instar the worms spin flimsy cocoons.
 Infected female moths lay pebrine contaminated eggs in lumps one above the
other.
 The number of eggs per laying is also drastically redused.

7. Symptoms
 Symptoms observed in all life stages viz., Egg, larva, pupa and adult.
Egg stage
 Poor egg number.
 Reduction in size and weight.
 Lack of adherence of substratum, ununiform with more of dead &
unfertilized eggs.
 Irregular hatching.

8. Larval stage
 Loss of appetite, retarded growth & ununiformity in size.
 Irregular moulting.
 Heavy mortality after 2nd moult if infected at egg stage.
 Larvae shrink in size and vomit gut juice.
 Dark brown or black spots may be seen sometimes on the body.

9. Pupal stage
 Pupa looks swollen.
 Irregular black spots on the body.
 Heavy mortality at pupal stage.

10. Moth stage
 Improper development of moth.
 Deformed wings & distorted antennae.
 Poor mating and egg laying.
 Scale of wings and abdominal area detach easily.