Veterinary Research, a journal on Animal Infection

The Rasa Aragonesa sheep is the second most important Spanish breed after the Merino breed. Reported here is the prion protein (PrP) haplotype frequency distribution for scrapie-related codons (136, 154 and 171) and a sequencing study of the complete PrP gene open reading frame for this breed and six other closely related breeds. The study includes four scrapie-affected sheep flocks belonging to Rasa Aragonesa and Rasa Navarra breeds. Thirty-eight scrapie-affected sheep, 502 healthy sheep from scrapie-affected flocks and 905 sheep from a breed survey were genotyped. The most frequent PrP haplotype in both scrapie and healthy flocks was ARQ, which was found at significantly higher frequency in scrapie-affected sheep. The susceptibility-associated VRQ haplotype was found at low frequencies in six out of eight breeds, but was not present in the 38 scrapie-affected sheep. The resistance-associated ARR haplotype was found in all breeds except one (Ojinegra) at frequencies ⩾14 %. Fourteen amino acid polymorphisms were detected in these Spanish sheep, including the known amino acid substitutions at codons 112, 136, 141, 143, 154, 171 and 176, and new polymorphisms at codons 101 (Q→R), 151 (R→G), 151 (R→H), 172 (Y→D) and 175 (Q→E). Most of the novel polymorphic codons show frequencies lower than 5 %.

Bovine spongiform encephalopathy (BSE) had never been detected in Sweden until 2006, when the active surveillance identified a case in a 12-year-old cow. The case was an unusual form, because several molecular features of the protease-resistant prion protein (PrP^res) were different from classical BSE. The differences included higher susceptibility for proteinase K, higher molecular weight of the PrP^res bands, affinity to the N-terminus-specific antibodies 12B2 and P4, and peculiar banding pattern with antibody SAF84 showing an additional band at the 14 kDa position. The molecular characteristics were in accordance to previous descriptions of H-type BSE. This report shows that a range of Western blot techniques and antibodies can be applied to confirm H-type BSE and further describes that the ratio of the amounts of PrPres#1 and PrPres#2, after deglycosylation, depends on the antibody used during processing. Immunohistochemistry on sections of medulla at the level of the obex applying antibodies with epitopes covering a broad range of the PrP sequence showed accumulation of disease-specific PrP (PrP ^d ) in the gray matter. Fine punctate deposition in the neuropil was the most predominant type and was more severe in BSE target nuclei. The types of PrP ^d deposition are described in comparison with classical BSE. PrP-gene sequencing showed 6 copy octarepeat alleles and no abnormalities. It is postulated that the disease had a spontaneous origin, rather than having had been acquired in the BSE epidemic.

Bovine Spongiform Encephalopathy (BSE) is the only animal prion which has been recognized as a zoonotic agent so far. The identification of BSE in two goats raised the need to reliably identify BSE in small ruminants. However, our understanding of scrapie strain diversity in small ruminants remains ill-defined, thus limiting the accuracy of BSE surveillance and spreading fear that BSE might lurk unrecognized in goats. We investigated prion strain diversity in a large panel of European goats by a novel experimental approach that, instead of assessing the neuropathological profile after serial transmissions in a single animal model, was based on the direct interaction of prion isolates with several recipient rodent models expressing small ruminants or heterologous prion proteins. The findings show that the biological properties of scrapie isolates display different patterns of geographical distribution in Europe and suggest that goat BSE could be reliably discriminated from a wide range of biologically and geographically diverse goat prion isolates. Finally, most field prion isolates showed composite strain features, with discrete strain components or sub-strains being present in different proportions in individual goats or tissues. This has important implications for understanding the nature and evolution of scrapie strains and their transmissibility to other species, including humans.