A total of 51 goats, including seven clinical cases, from the first herd in Greece reported to have scrapie was examined to discern an association between scrapie susceptibility and polymorphisms of the gene encoding the prion protein (PrP). Each animal was evaluated for clinical signs of the disease, histopathological lesions associated with scrapie, the presence of detectable proteaseresistant PrP in the brain and PrP genotype. Eleven different PrP genotypes encoding at least five unique predicted mature PrP amino acid sequences were found. These genotypes included the amino acid polymorphisms at codons 143 (H R) and 240 (S P) and ' silent ' nucleotide alterations at codons 42 (a g) and 138 (c t). Additionally, novel caprine amino acid polymorphisms were detected at codons 21 (V A), 23 (L P), 49 (G S), 154 (R H), 168 (P Q) and 220 (Q H) and new silent mutations were found at codons 107 (g a) and 207 (g a). The following variants were found in scrapie-

A total of 216 local crossbred sheep from 16 scrapie-affected Greek flocks and 210 purebred sheep of the milk breeds Chios and Karagouniko from healthy flocks were analysed for scrapie-linked polymorphisms in the prion protein (PrP) gene. Of the 216 sheep in this case-control study, 96 sheep were clinical cases, 25 subclinical cases (asymptomatic at the moment of euthanasia but positive by histopathology and/or ELISA detecting proteinase-resistant PrP) and 95 healthy controls (negative by all evaluations). Polymorphisms at codons 136, 154 and 171 were determined by denaturing gradient gel electrophoresis, followed by RFLP and sequencing. Scrapie, both clinical and subclinical, was associated with the genotypes ARQ/ARQ (88 of 110 sheep of that genotype), ARQ/TRQ (9 of 13), ARQ/AHQ (15 of 38) and VRQ/VRQ (9 of 17). Histopathological lesions were more severe in the clinical cases. Genotypes ARQ/ARR (26 sheep), ARQ/ARK (seven sheep), AHQ/ARR (one sheep), ARH/ARH (one sheep) and ARR/ARH (three sheep) were detected exclusively in healthy control sheep. In the purebred survey, four genotypes were present in the Chios sheep (ARQ/ARQ, ARQ/TRQ, ARQ/AHQ and ARQ/ARR) and four in the Karagouniko sheep (ARQ/ARQ, ARQ/AHQ, ARQ/ARR and ARQ/ARH). INTRODUCTIONScrapie is an infectious neurodegenerative fatal disease of sheep and goats belonging to the group of transmissible subacute spongiform encephalopathies (TSEs), along with bovine spongiform encephalopathy (BSE), chronic wasting disease and Creutzfeldt-Jakob disease. All TSEs are characterized by long incubation periods, disturbances in behaviour and movement, degeneration in tissues of the central nervous system (CNS) and accumulation of an abnormal isoform of the host-encoded cellular prion protein in tissues of the CNS. It has been hypothesized that these diseases are attributable to a conformational change in the prion protein (PrP), which results in a change from a predominantly a-helical protein to a b-sheet form (Prusiner, 1996). Normal PrP protein (PrP c ) is a cell-surface glycoprotein, the expression of which is necessary for the production of prions (Büeler et al., 1993;Prusiner et al., 1993). PrP c is expressed in most tissues of the body, with the nervous tissues showing the highest PrP c expression levels (Bendheim et al., 1992;Horiuchi et al., 1995).In several animal species and in humans, polymorphisms within the open reading frame of the PrP gene are associated with the occurrence and the pathological lesions of TSEs (Pocchiari, 1994). The incidence of natural scrapie is strongly influenced by alterations in the host gene that encodes the PrP (Hunter, 1997). Such polymorphisms may influence the conversion of PrP c into the pathogenic isoform . The mechanism by which the individual allelic variants lead to altered susceptibility or incubation periods has not been elucidated. It has been proposed that in humans PrP polymorphisms may be present at critical sites involved in the conformational transition from PrP c to PrP Sc (Glockshuber et al., 1999). The study o...

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During the past six years 623 cases of coenurosis (gid) in sheep have been treated surgically. Cysts were removed successfully from 573 of them (92 per cent) and 517 (83 per cent) were able to return to their flocks, although 36 showed no clinical improvement In 37 cases, the cyst could not be localised, and postmortem examinations showed that in nine cases the cyst was in the brainstem, and in 28 cases it was in the cerebellum. Fifty-six cases deteriorated gradually after surgery and in these cases more than one cyst was found postmortem. Thirteen cases died during surgery.

The first cases of scrapie were detected in Greece in a flock of sheep in October 1986. All the animals of the affected flock and all sheep in two flocks that were in contact were killed and buried. A systematic investigation of all available cases with signs indicating a neurological disease started in sheep and goats in late 1986, as well as in cattle in 1989. The investigation was based on clinical examination, necropsy or macroscopical examination of the brain and viscera, and histological examination of the brain in all animals except those with coenurosis. Histological examinations of specimens from the spinal cord and other tissues, and if considered necessary bacteriological, toxicological and serological examinations were also carried out. In October 1997, scrapie was diagnosed in sheep of a second flock (a mixed flock of sheep and goats), grazing in a pasture close to the place where scrapie was initially detected. All animals of the second flock were also killed and buried. Diagnosis in the first flock was based on clinical signs and histological lesions, and in the second immunoblotting was also used. Distinctive lesions of scrapie were found in the brain and/or the spinal cord of eight sheep with clinical signs from the two flocks. The lesions were revealed in the brain stem and/or in the cervical spinal cord, and tended to be symmetrical. In one sheep, severe lesions in the cortex of cerebral hemispheres and of the cerebellum were also found. In the brain of two sheep from the second flock the pathological isoform of PrP protein was detected. Despite the eradication scheme applied, scrapie in sheep reappeared after 11 years in a place close to where it occurred initially. This may indicate that the effectiveness of the eradication scheme implemented was not adequate and additional approaches may be needed.