Short Communication Putative emergence of classical scrapie in a background of enzootic atypical scrapie

Active transmissible spongiform encephalopathy (TSE) surveillance in small ruminants acrossEurope was implemented in 2002 following the epizootic of bovine spongiform encephalopathy.Here, we report the potential emergence of classical scrapie in Portugal, in a background ofenzootic atypical scrapie. Between 2003 and 2008, 375459 small ruminants were screened intotal, with 328 animals confirmed positive for NOR98 atypical scrapie. During this period, theprevalence rate of atypical scrapie for all years combined was 0.0874% across the country. In thisscenario, classical scrapie emerged as a single outbreak in 2008, with 12 identified cases. Incontrast to other European countries, where classical scrapie has been enzootic for decades,these data indicate that, in Portugal, atypical scrapie is the predominant form of TSE. The findingsreported here will have implications for the control of classical scrapie in Portugal, namely in termsof keeping the country free of enzootic classical scrapie.