Detection and Clinical Evolution of Scrapie in Sheep by 3rd Eyelid Biopsy

Abstract

The goal of this article was to characterize the clinical evolution of scrapie in naturally affected sheep. Eighteen sheep with scrapie diagnosed by examination of 3rd eyelid biopsy and 12 control ewes were studied throughout the duration of their disease. Diagnosis was confirmed postmortem by histopathologic, immunohistochemical, and Western blot analysis of nervous tissue. Complete clinical examinations were performed every 2 weeks for each animal, of which 3 clinical examinations per animal are reported. Those clinical signs that showed a significant frequency within the corresponding clinical examination were considered representative of each stage of the disease (ie, early, middle, and late). The representative clinical signs for the early stage were hypoesthesia in the limbs, alteration of mental status, and a body condition score ,3. Remarkably, hypoesthesia in the limbs was one of the 1st signs appearing during the early clinical stage in the affected animals, even before the appearance of other signs. For the middle stage, representative signs were the same as those for the early stage, together with hyporreflexia in the limbs, cardiac arrhythmia, pruritus/wool loss, and the appearance of the nibbling reflex. Representative clinical signs for the late stage were the same as those for the early and middle stage, together with head tremors, hyperexcitability to external stimuli, ataxia or gait abnormalities, and teeth grinding. On the basis of these results, we propose the calculation of an objective clinical index that allows the differentiation among clinical stages and that could be useful for further studies. The usefulness of 3rd eyelid lymphoid tissue biopsies for sequential clinical studies in naturally scrapie-affected sheep is demonstrated.

Codon 141 polymorphisms of the ovine prion protein gene affect the phenotype of classical scrapie transmitted from goats to sheep

“…For example, the survival time was not necessarily longer in sheep with a higher PrP sc score (1452 was culled later than 1424 even though the total PrP sc was two times higher in 1424). Studies on the clinical progression in naturally affected sheep with scrapie suggested that head tremor, ataxia, teeth grinding, loss of body condition and loss of a menace response occurred more frequently with disease progression [29, 40]. There was some indication that sheep with higher PrP sc scores, which had been challenged with milk or brain from the same donor, presented with more severe clinical signs: both brain-challenged VV sheep with a lower PrP sc score (1452 and 1425) were not ataxic and had a menace response unlike the other VV sheep (1424), which was ataxic, lost the menace response and had a considerably higher PrP sc score.…”

Clinical findings in two cases of atypical scrapie in sheep: a case report

“…2) suggests a higher level of PrP res accumulation in the brainstem, which may indicate that this sheep was in a more advanced clinical stage. As the disease progresses scrapie cases are more likely to react to the scratch test, which was seen in case 05/377, but they also more frequently display head tremor, teeth grinding and an absent menace response [2,22], as seen in case 06/008, and argues against clinical duration being responsible for the observed differences.…”

Medulla oblongata transcriptome changes during presymptomatic natural scrapie and their association with prion-related lesions

“…Four of the animals exhibited preclinical signs of scrapie, and the diagnoses were made by third eyelid biopsies [26] and confirmed using the rapid test (TeEsE, Bio-Rad) and immunohistochemistry to detect PrP Sc using the 6 H4 monoclonal antibody [27]. This characterization was performed considering the presence of the clinical signs associated with the disease as per previously reported criteria [26].…”

“…This characterization was performed considering the presence of the clinical signs associated with the disease as per previously reported criteria [26]. All of the animals belonged to flocks that had been previously characterized as scrapie-affected flocks and were located in different geographical areas.…”