Flacherie (literally: "flaccidness") is a disease of silkworms, caused by silkworms eating infected or contaminated mulberry leaves. Flacherie infected silkworms look weak and can die from this disease. Silkworm larvae that are about to die from Flacherie are a dark brown.
There are two (or three) kinds of flacherie: basically, infectious (viral) flacherie and noninfectious (touffee) flacherie. Both are technically a lethal diarrhea.
Touffee flacherie is caused by heatwaves (touffee means "sudden heat spell" in French).
Viral flacherie is ultimately caused by infection with Bombyx mori infectious flacherie virus (BmIFV, Dicistroviridae), Bombyx mori densovirus (BmDNV, Parvoviridae) or Bombyx mori cypovirus 1 (BmCPV-1, Reoviridae). This either alone or in combination with bacterial infection destroys the gut tissue. Bacterial pathogens contributing to infectious flaccherie are Serratia marcescens, and species of Streptococcus and Staphylococcus in the form known as thatte roga.
Louis Pasteur, who began his studies on silkworms diseases in 1865, was the first one able to recognize that mortality due to viral flacherie was caused by infection. (Priority, however, was claimed by Antoine Béchamp[1].)