The infectious agents showing properties that differ from both viruses and viroids are called as Prions.
Prions are proteinaceous infectious particles.
They are unconventional and atypical viruses.
They have no nucleic acids at all protein being the only detectable component present in them.
It consists of a hydrophobic membrane protein called PrP (prion protein).
They are associated with six degenerative nervous system disorders in sheep and goats. The disorder is name Scrapie.