Abstract
The thermal therapy of three kinds of Bombyx virus infections was investigated.
The thermal therapy (37°C for 24 hours) of larvae infected with a flacherie virus (IFV) was most effectively achieved during the molt or within 12 hours after ecdysis. The heat treatment could be shortened up to 6 hours if it was performed just after ecdysis. The larvae, which had been administered with a lethal dose of IFV just after hatching, did not succumb to the disease but made cocoons when repeatedly treated at 37°C for 24 hours at each larval ecdysis (four times).
The multiplication of the small flacherie virus (SFV) was inhibited at 37°C. When the SFV-infected larvae were reared at 27°C after infection, the amount of SFV antigen, which was estimated by a single radial immunodiffusion test, of the midgut increased with time, but reduced at larval ecdysis. In addition, when the larvae were transferred from 27°C to 37°C after ecdysis, the reduction of SFV antigen was continued.
The formation of cytoplasmic polyhedra was apparently inhibited at 37°C. When the larvae infected with cytoplasmic-polyhedrosis virus (CPV) were reared at 27°C, the CPV-infected cells were discharged from the midgut epitherium at ecdysis and the newly regenerated cells appeared at its place.
These results suggest the possibility of cure the larvae infected with SFV or CPV as well as IFV by thermal therapy at the time of larval ecdysis.
