Guidance developed for atypical BSE
The European Union (EU) agency was asked to develop the guidance by the European Commission, which is concerned about gaps in knowledge of such outbreaks. An EFSA note said that, so far, 80 cases of atypical BSE have been reported by EU member states since 2001. It said: "All atypical BSE cases have been detected by active surveillance, typically in animals over eight years of age, with a similar number of cases detected each year."
It added: "Current knowledge on atypical BSE is limited and the implementation of this protocol will contribute to fill information gaps."
Atypical BSE can have a wide range of unusual and unexpected characteristics. For example, cases seem not to be transmitted through infected feed, as with standard BSE, but rather can occur sporadically among older cows.
Under the protocol, disease specialists would launch further studies into atypical BSE, with new "studies aimed at investigating the presence, distribution and relative level of infectivity of atypical BSE", said EFSA. The guidance advises on the minimum number of animals that should be tested to secure an adequate sample and on how tissues should be prepared, processed and tested. It also advises on methods that should be used to identify abnormal prions that can indicate BSE and quantify infectivity. And it gives further advice on how tissue obtained through earlier BSE studies could be used to research ‘atypical’ cases, for instance through the EU’s ‘EURL’ study (the European Union Reference Laboratory (EURL) for Transmissible Spongifom Encephalopathies - TSEs).
"Material from other studies could be used to augment the range of SRM [specified risk material] and non-SRM tissues available," added the EFSA note. But this is unlikely to be enough, so new experiments would have to be considered, it added. These should be assessed to collect information on the performance of currently validated rapid tests for BSE in cattle and sample tissues, the report concluded.
