Institute of Novel and Emerging Infectious Diseases (INNT)

The FLI is appointed as the national reference laboratory for all forms of TSEs in animals.

TSEs include a number of diseases, such as Bovine Spongiform Encephalopathy (BSE) in cattle, scrapie (scrapie) in sheep and goats, Chronic Wasting Disease (CWD) in deer, Transmissible Mink Encephalopathy (TME) in mink, Feline Spongiform Encephalopathy (FSE) in cats, and Camel Prion Disease (CPD) in camels.

All TSEs are infectious neurodegenerative diseases, always fatal, which and classified as prion diseases within the group of protein misfolding diseases. Causative is the conversion of the cellular membrane bound prion protein (PrPc) into a partially protease-resistant pathological form (PrPSc), which is deposited in the central nervous system of affected animals. Infection occurs orally via contaminated feed or, with the exception of BSE, via contaminated pasture. All TSEs are characterized by long incubation periods of several months to years. The clinical picture of the disease therefore only occurs in adult animals and depends on the species affected and the prion strain present. However, clinical signs includes usually behavioral changes (e.g., segregation from the herd, nervousness), neurological deficits (e.g., movement disorders, tremor, hyperesthesia), and progressive emaciation with preserved appetite. Sheep, in particular, also frequently exhibit marked pruritus.

There is a genetic predisposition to the disease in small ruminants and cervids. Point mutations in the prion protein gene, resulting in the replacement of individual amino acids in the structure of the prion protein, may contribute to increased susceptibility or resistance to the disease. This is specifically used in small ruminants to eradicate the disease, among other things, through breeding influence.

The classical prion diseases usually occur at an age of 2-5 years, this concerns in particular classical BSE in cattle, classical scrapie in sheep and goats, as well as CWD in cervids. 

In older animals, on the other hand, so-called Atypical TSE forms are observed, which are considered sporadic age-associated diseases of spontaneous origin and are very difficult or impossible to transmit under natural conditions. These include Atypical H- and L-type BSE in cattle and Atypical scrapie in small ruminants. With the emergence of CWD in northern Europe, similar prion strains have also been detected in elk and red deer. However, their exact characterization is still ongoing.

BSE is a zoonosis and can also occur in other animal species. Natural transmission has been demonstrated for humans (variant Creutzfeldt-Jakob disease), felids (Feline Spongiform Encephalopathy, FSE), and in goats. Experimentally, sheep and several rodents can also be infected. The extent to which CWD is transmissible to humans or other animal species has not yet been conclusively determined, but the risk is currently assumed to be very low.

In accordance with Regulation EU 999/2001, a BSE and scrapie surveillance program is carried out in the EU using rapid test methods (active surveillance). Only tests approved for the examination of these species may be used (see list below). However, confirmation of a reactive test result or all other suspected cases must be carried out at the National Reference Laboratory (NRL) for TSEs at the FLI on Riems Island.

All relevant diagnostic methods for the detection of PrP^Sc, which also serves as a marker of the disease, are established at the NRL. These tests also discriminating between Atypical and Classical TSE forms. Only methods recognized by the World Organization for Animal Health (OIE) may be used. These include immunohistochemical examinations, biochemical methods (so-called OIE-SAF immunoblot), the combination of different rapid test systems and, in cases of doubt, the detection of infectivity in the mouse model.