Epidemiology - Slow Diseases Caused by Prions

Epidemiology

Prion-related diseases are rare but worldwide.

◗ Geographical distribution

Creutzfeldt–Jakob disease is rare but is found throughout the world with an incidence of about one case per million populations. An autosomal dominant pattern of inheritance linked to mutation in the PrP gene is found in nearly 10% cases of familial CJD. Till 2003, a total of 167 definite and probable cases of vCJD have been reported worldwide. Most of the cases of vCJD have been reported in the United Kingdom. The condition is yet to be documented from Asia. Creutzfeldt–Jakob disease syndrome and fatal familial insomnia (FFI) in humans are rare but occur in different parts of the world.

◗ Reservoir, source, and transmission of infection

The spongiform encephalopathies caused by prions may be infectious, hereditary, and sporadic. The CJD, GSS, and FFI are inheritable. The CNS tissue in CJD has the highest concentra-tion of prion agent, hence is the most important source of infection. Unlike the prion disease, in vCJD, lymphoid tissues show highest concentration of prions. Contaminated blood is another source of infection.

Families with genetic history of the disease have been identified in cases of GSS syndrome. Hosts and pathogenesis of prion-related slow diseases in animals are summarized in Table 69-4.