In spring 2011, two new cases of BSE were discovered in Switzerland. Both cases were detected using the Prionics^®-Check BSE tests. A report has now been published showing that these cases represent a novel type of BSE. What are the consequences of these new BSE cases?

After a period of four years without BSE positive cows, in spring this year Switzerland was shaken by the discovery of two new BSE cases detected only one month apart from each other. The cases appeared in different areas of Switzerland and involved animals aged 8 and 15 years, which were tested with the Prionics^®-Check BSE tests as part of the active disease surveillance program. Bettina Bernhard, Head of the Prionics diagnostic laboratory reported that: “It was the first time in 4½ years that we had found a BSE positive sample in our laboratory. Based on the results from the Prionics^®-Check WESTERN, we immediately saw that the fingerprint of the prion protein was not that of the classical BSE cases we have detected before. We then informed the Swiss National Reference Laboratory and veterinary authorities and the positive result was confirmed with the Prionics^®-Check PrioSTRIP.” 

Novel type of BSE?
BSE cases that differ from the classical BSE strain have been detected before, however, with low incidence. These atypical strains, designated BASE/L-BSE and H-BSE, were first reported in 2004 in Italy and France. Both strains were detected as part of routine surveillance using the Prionics^®-Check WESTERN and ELISA tests. The recent publication by Torsten Seuberlich of the Swiss National and OIE¹ Reference Laboratories for BSE and Scrapie and his colleagues, is showing that these two Swiss cases not only differ from classical BSE, but also from the atypical BSE cases found in other countries (see figure "Fingerprint of prion proteins"). It appears that the two BSE cases detected in Switzerland seem to represent a novel type of atypical BSE. Dr. Seuberlich explains: “We are now undertaking further investigations into these two cases and until there is more clarity, surveillance should continue to be carried out at a high level and disease awareness should be increased. Furthermore, we have to ensure that diagnostic techniques are applied that identify such cases.”

Continued vigilance needed
Whereas consumption of meat from cows affected by classical BSE has been associated with vCJD, the public health hazard from atypical BSE is unclear. Little is known about its origin and whether it can be transmitted to other animals. These cases show, however, that BSE has not been completely eradicated and that the disease can continue to occur even with current preventive measures (e.g. the meat-and-bone meal ban) in place. The appearance of new strains of the prion protein could also indicate that BSE is still evolving. Continuous monitoring will be needed to keep these new strains under surveillance.

¹World Organisation for Animal Health