In which disease of silkworm skin becomes rubbery and dull in appearance?

In Pebrine disease silkworm skin becomes rubbery and dull in appearance.
Pebrine, or "pepper disease," is a disease of silkworms, which is caused by protozoan microsporidian parasites. The parasites infect eggs and are therefore transmitted to the next generation.
The silkworm larvae infected by pebrine are usually covered in brown dots and are unable to spin silkworm thread.