Final answer:
Prion diseases can be transmitted through mutation in the germline PrP gene, contaminated medical instruments and implants, and ritualistic cannibalism. Secondary transmission has also occurred via blood transfusion. Prions remain resistant to typical sterilization methods, making prevention particularly challenging.
Step-by-step explanation:
Prions, which are infectious proteins, have been known to transmit diseases in several ways beyond oral consumption of infected tissues. One such method is mutation in germline PrP gene, where hereditary forms of prion diseases are due to mutations in the gene that encodes the prion protein. Medical procedures can also be a route of transmission, as indicated by cases of prion diseases being passed through contaminated neurosurgical instruments, corneal grafts, and pituitary growth hormones derived from human cadavers. Additional transmission has been documented secondary to blood transfusion. In terms of non-medicinal transmission, prions have been associated with ritualistic cannibalism in the case of kuru among the Fore tribe in Papua New Guinea, where the disease was spread by consuming nervous tissue from affected individuals within the community. Preventing the spread of prion diseases is challenging since prions are notoriously resistant to standard sterilization methods such as autoclaving, phenol, alcohols, formalin, and B-propiolactone; they can remain infectious even after such treatments.