ABSTRACT
Flacherie diseases of the silkworm, Bombyx mori, are major factors causing serious loss of cocoon production in sericultural countries. Flacherie is a general term for silkworm diseases with flacidity symptoms. K. Aizawa and colleagues isolated a nonoccluded virus from silkworm with flacherie symptoms and called it the infectious flacherie virus (IFV). IFV isolated from the silkworm is also infectious to the mulberry wild silkworm, Bombyx mandarina, an insect pest of field mulberry. The target of IFV is the goblet cell of the midgut epithelium, and the virus multiplies in the cytoplasm, eventually disintegrating the cell. Younger larvae are more susceptible to IFV than older larvae. Electron microscope observations on the midgut infected with IFV revealed that, in an early stage of infection, membrane-bound vesicles which were specifically induced by the virus infection were formed in the cytoplasm of goblet cell. In the portion adjacent to the specific vesicles, virus particles appeared.
