Species and Strain Glycosylation Patterns of PrPSc

). Both PrP isoforms bear two potential glycosylation sites and thus in a typical western blot with an anti-PrP antibody three distinct bands appear, corresponding to the di-, mono- or unglycosylated forms of the protein. The relative intensity and electrophoretic mobility of the three bands are characteristic of each TSE strain and have been used to discriminate between them. protein. and could play an accessory role in the appearance of some of the characteristic features of TSE strains. The differences in sugar composition could also be used as an additional tool for discrimination between the various TSEs

The evaluation of exposure risks for natural transmission of scrapie within an infected flock

Background: Although the epidemiology of scrapie has been broadly understood for many years, attempts to introduce voluntary or compulsory controls to eradicate the disease have frequently failed. Lack of precision in defining the risk factors on farm has been one of the challenges to designing control strategies. This study attempted to define which parts of the annual flock management cycle represented the greatest risk of infection to naive lambs exposed to the farm environment at different times.Results: In VRQ/VRQ lambs exposed to infected sheep at pasture or during lambing, and exposed to the buildings in which lambing took place, the attack rate was high and survival times were short. Where exposure was to pasture alone the number of sheep affected in each experimental group was reduced, and survival times were longer and related to length of exposure.Conclusion: At the flock level, eradication and control strategies for scrapie must take into account the need to decontaminate buildings used for lambing, and to reduce (or prevent) the exposure of lambs to infected sheep, especially in the later stages of incubation, and at lambing. The potential for environmental contamination from pasture should also be considered. Genotype selection may still prove to be the only viable tool to prevent infection from contaminated pasture, reduce environmental contamination and limit direct transmission from sheep to sheep

Minimum Effective Dose of Cattle and Sheep BSE for Oral Sheep Infection.

The minimum dose required to cause infection of Romney and Suffolk sheep of the ARQ/ARQ or ARQ/ARR prion protein gene genotypes following oral inoculation with Romney or Suffolk a sheep Bovine spongiform encephalopathy (BSE)-derived or cattle BSE-derived agent was investigated using doses ranging from 0.0005g to 5g. ARQ/ARQ sheep which were methionine (M) / threonine (T) heterozygous or T/T homozygous at codon 112 of the Prnp gene, dosed ARQ/ARR sheep and undosed controls did not show any evidence of infection. Within groups of susceptible sheep, the minimum effective oral dose of BSE was found to be 0.05g, with higher attack rates following inoculation with the 5g dose. Surprisingly, this study found no effect of dose on survival time suggesting a possible lack of homogeneity within the inoculum. All clinical BSE cases showed PrPd accumulation in brain; however, following cattle BSE inoculation, LRS involvement within Romney recipients was found to be significantly lower than within the Suffolk sheep inoculated group which is in agreement with previous reports

Frequency of accumulation of PrP^d in the LRS tissues of BSE positive sheep.

<p>Frequency of accumulation of PrP^d in the LRS tissues of BSE positive sheep.</p

Minimum Effective Dose of Cattle and Sheep BSE for Oral Sheep Infection - Fig 2

<p>Survival curves of sheep that developed IHC-confirmed BSE according to: a) source and dose of inoculum: dark blue, sheep inocula at 5g dose; light blue, sheep inocula at 0.5/0.05g dose; red, cattle inoculum at 5g dose; orange, sheep inocula at 0.5/0.05g dose. b) recipient breed and dose of inoculum: dark green, Suffolk sheep dosed with 5g; light green, Suffolk sheep dosed with 0.5/0.05g; purple, Romney sheep dosed with 5g; pink, Romney sheep dosed with 0.5/0.05g. Note that in both graphs, most sheep succumbed between ~600 and 1,150 days regardless of dose received and that the few sheep that survived for longer than ~1,150 days did so also regardless of the dose they received.</p

Graphical and schematic representation of the outcome of the experiments in terms of attack rates and survival times.

<p>Attack rates (%), black bars inside white boxes, with actual values next to them. Survival times are indicated as average±SD dpi (age in case of undosed controls). Note that despite the marked differences in AR between the 5g and the 0.5/0.05g doses, STs are very similar with the only significant difference marked as * (for details refer to text).</p

Experimental design.

<p>Experimental design.</p