The interpretation of disease phenotypes to identify TSE strains in mice: characterisation of BSE using PrPSc distribution patterns in the brain.

In individual animals affected by transmissible spongiform encephalopathies, different disease phenotypes can be identified which are attributed to different strains of the agent. In the absence of reliable technology to fully characterise the agent, classification of disease phenotype has been used as a strain typing tool which can be applied in any host. This approach uses standardised data on biological parameters, established for a single host, to allow comparison of different prion sources.

Studies of the transmissibility of the agent of bovine spongiform encephalopathy to the domestic chicken.

Background: Transmission of the prion disease bovine spongiform encephalopathy (BSE) occurred accidentally to cattle and several other mammalian species via feed supplemented with meat and bone meal contaminated with infected bovine tissue. Prior to United Kingdom controls in 1996 on the feeding of mammalian meat and bone meal to farmed animals, the domestic chicken was potentially exposed to feed contaminated with the causal agent of BSE. Although confirmed prion diseases are unrecorded in avian species a study was undertaken to transmit BSE to the domestic chicken by parenteral and oral inoculations.

Paraffin-embedded tissue blot as a sensitive method for discrimination between classical scrapie and experimental bovine spongiform encephalopathy in sheep.

The paraffin-embedded tissue (PET) blot was modified for use as a tool to differentiate between classical scrapie and experimental bovine spongiform encephalopathy (BSE) in sheep. Medulla (obex) from 21 cases of classical scrapie and 6 cases of experimental ovine BSE were used to develop the method such that it can be used as a tool to differentiate between BSE and scrapie in the same way that differential immunohistochemistry (IHC) has been used previously. The differential PET blot successfully differentiated between all of the scrapie and ovine BSE cases.

A retrospective immunohistochemical study reveals atypical scrapie has existed in the United Kingdom since at least 1987.

Atypical scrapie is a relatively recent discovery, and it was unknown whether it was a new phenomenon or whether it had existed undetected in the United Kingdom national flock. Before 1998, the routine statutory diagnosis of transmissible spongiform encephalopathy (TSE) in sheep relied on the presence of TSE vacuolation in the brainstem. This method would not have been effective for the detection of atypical scrapie.

Transmissibility studies of vacuolar changes in the rostral colliculus of pigs.

Background: Histopathological examinations of brains from healthy pigs have revealed localised vacuolar changes, predominantly in the rostral colliculus, that are similar to the neuropil vacuolation featured in the transmissible spongiform encephalopathies and have been described in pigs challenged parenterally with the agent causing bovine spongiform encephalopathy (BSE). Feedstuff containing BSE-contaminated meat and bone meal (MBM) may have been fed to pigs prior to the ban of mammalian MBM in feed of farmed livestock in the United Kingdom in 1996, but there is no evidence of the natural occurrence of a transmissible spongiform encephalopathy (TSE) in the domestic pig. Furthermore, experimental transmission of BSE to pigs by the oral route has been unsuccessful.

Atypical scrapie in sheep from a UK research flock which is free from classical scrapie.

Background: In the wake of the epidemic of bovine spongiform encephalopathy the British government established a flock of sheep from which scrapie-free animals are supplied to laboratories for research. Three breeds of sheep carrying a variety of different genotypes associated with scrapie susceptibility/resistance were imported in 1998 and 2001 from New Zealand, a country regarded as free from scrapie. They are kept in a purpose-built Sheep Unit under strict disease security and are monitored clinically and post mortem for evidence of scrapie.

A collaborative Canadian-United Kingdom evaluation of an immunohistochemistry protocol to diagnose bovine spongiform encephalopathy.

Collaboration was established in 2001 to evaluate a commercially available immunohistochemistry assay kit for the detection of bovine spongiform encephalopathy (BSE) disease-associated prion protein in formic acid-treated formalin-fixed samples of bovine brain. The kit protocol was evaluated at the National Centre for Foreign Animal Diseases (Winnipeg, Canada) and the Veterinary Laboratories Agency (Weybridge, U.K.

Experimental transmission of atypical scrapie to sheep.

Background: Active surveillance for transmissible spongiform encephalopathies in small ruminants has been an EU regulatory requirement since 2002. A number of European countries have subsequently reported cases of atypical scrapie, similar to previously published cases from Norway, which have pathological and molecular features distinct from classical scrapie. Most cases have occurred singly in flocks, associated with genotypes considered to be more resistant to classical disease.

Bovine spongiform encephalopathy infectivity in greater kudu (Tragelaphus strepsiceros).

Of all the species exposed naturally to the bovine spongiform encephalopathy (BSE) agent, the greater kudu (Tragelaphus strepsiceros), a nondomesticated bovine from Africa, appears to be the most susceptible to the disease. We present the results of mouse bioassay studies to show that, contrary to findings in cattle with BSE in which the tissue distribution of infectivity is the most limited recorded for any of the transmissible spongiform encephalopathies (TSE), infectivity in greater kudu with BSE is distributed in as wide a range of tissues as occurs in any TSE. BSE agent was also detected in skin, conjunctiva, and salivary gland, tissues in which infectivity has not previously been reported in any naturally occurring TSE.

In situ detection of cellular and abnormal isoforms of prion protein in brains of cattle with bovine spongiform encephalopathy and sheep with scrapie by use of a histoblot technique.

To detect prion protein, brains from 5 cattle naturally affected with bovine spongiform encephalopathy (BSE) and 3 sheep naturally affected with scrapie were examined and compared with brains of normal cattle and sheep using a histoblot technique. The technique enabled the in situ distinctive detection of the cellular (PrP(C)) and abnormal (PrP(Sc)) isoforms of the prion protein. In BSE- or scrapie-affected brains, the Prp(C) signal decreased, especially in those areas where the PrP(Sc) signal was detected.