Bovine spongiform encephalopathy: Atypical and classical

Atypical BSE (H type and L type)

• Develops spontaneously in any cattle population
• Transmission to humans has never been reported
• The 2 types of atypical BSE (H and L) were identified in 2004
  • It is a very rare disease, and is expected to occur in all cattle populations, regardless of the control measures in place
• Has worldwide distribution, even in countries where no classical BSE has been reported
• Its occurrence is not considered for the purpose of the official BSE risk status recognition by the World Organisation for Animal Health (WOAH)
• The vast majority of cases worldwide (about 92%) have been detected in animals 8 years or older
  • The youngest case reported to date was 67 months old
• 3 cases in Canada (2 H-type and 1 L-type); the last case was reported in 2021

Classical BSE

• Occurs through an animal's consumption of prion contaminated feed
• Can cause variant Creutzfeldt-Jakob disease in humans through the consumption of contaminated beef
• Was first diagnosed in cattle in 1986
  • The implementation of appropriate control measures resulted in its decline worldwide
  • Today, there are few scattered cases of classical BSE in the world as part of the tail end of the epidemic
• Cases have been reported in more than 20 countries
• Its occurrence may be considered for the purpose of the official BSE risk status recognition by the WOAH
• Can affect cattle of any age
  • The youngest case reported to date was 20 months old
• 17 cases in Canada, the last case in 2015
• Cattle get infected during the first year of life and show clinical signs after 5 to  years
  • The youngest case reported to date was 20 months old
  • 17 cases in Canada; the last case was born in 2009