Amplification of H- and L-type BSE in the natural host

Atypical Bovine Spongiform Encephalopathy (BSE), comprising H-type and L-type BSE forms, was first detected by active surveillance in 2004 and continues to be reported at a low incidence throughout Europe. Limited understanding of its origin, zoonotic potential and pathogenesis complicates European disease management and control. To gain knowledge on the tissue distribution, review the specificity and sensitivity of in vitro diagnostic tests and investigate aetiological correlations between atypical and classical BSE, an animal trial in 22 Frisian Holstein cattle has been started in April 2025. Per atypical BSE type, ten calves were inoculated intracerebrally with 10% homogenates of German field cases. Two additional animals serve as mock control. During the incubation period all cattle undergo regular clinical-neurological examinations to define the exact time point for euthanasia. Additionally, samples of blood and cerebrospinal fluid are collected regularly. At necropsy, besides the brain and spinal cord, tissue samples, in particular from the peripheral nervous and the lymphoreticular system will be taken under prion-sterile conditions. For confirmation of prion infectivity, brain stem samples will be investigated by ELISA, immunohistochemistry and discriminatory immunoblot.

This animal trial allows to propagate novel material of H- and L-type BSE infected cattle for future research studies and critically, certified reference material for interlaboratory proficiency testing. Requests for certain tissues and body fluid samples other than brain and spinal cord can still be met. The knowledge gained from this study will serve to adjust current BSE regulations and control strategies within the European Union.