Bovine spongiform encephalopathy: diagnostic significance of vacuolar changes in selected nuclei of the medulla oblongata

Abstract

The adequacy of a histopathological diagnosis of bovine spongiform encephalopathy (BSE) based exclusively on observations of neuroparenchymal vacuolation in three specific neuroanatomic nuclei was tested by using a standard coronal section of medulla oblongata cut at the obex. The agreement between the observations and the definitive histopathological diagnosis was assessed in each of 684 bovine brains - 563 confirmed cases of BSE, 20 with changes which did not diagnose BSE conclusively and 101 in which the lesions of BSE were not detected. When the assessment was confined to the solitary tract nucleus and the spinal tract nucleus of the trigeminal nerve a positive result was obtained in 99.6 per cent of confirmed cases of BSE and only 1 per cent of brains in which lesions of BSE were not detected gave a false positive result. Thus an initial examination of the single section, together with an examination of representative areas of the rest of the brain when no unequivocal lesion was found, provided a satisfactory method for the routine diagnosis of BSE.

Experimental Classical Bovine Spongiform Encephalopathy

“…3,6,7,15,30,33,36,42,50,55,58,60,63,68,70 Based initially on spongiform changes and examination of large case numbers, the invariable predominance of lesions in the brainstem established this and, specifically, the medulla oblongata as the predilection brain region for diagnostic sampling. 18,30,53,63,66,68,70 Correlation of the highest concentrations of PrP Sc in the brainstem with the greatest degree of spongiform change 30,43,51,68 is considered suggestive of the initial brain pathologic alternations in BSE occurring in this region, consistent with the proposed pathogenesis of transmissible spongiform encephalopathy (TSE) in ruminants and laboratory rodent models after oral exposure. 4,5,13,20,26,29,39,40,61 This is supported by observations in a subset of clinical cases with restricted PrP Sc accumulation, which was invariably confined to the brainstem.…”

“…57 The medulla oblongata currently remains the anatomic predilection site for application of diagnostic tests in passive and active surveillance. 18,38,63,68 Where active surveillance is employed for BSE, it is important to establish if and to what extent this defined phenotype is expressed preclinically and therefore whether diagnostic approaches used in passive surveillance, including sampling and test method, are applicable during the incubation period.…”

The use of non-prion biomarkers for the diagnosis of Transmissible Spongiform Encephalopathies in the live animal

“…The reported technique relies on high-resolution electrocardiography (ECG) which can reveal abnormal heart rate variability (respiratory sinus arrhythmia or RSA) in the early stages of TSE infection. It is thought that RSA is altered during BSE onset by prions from the gut passing along the vagus nerve into the solitary nucleus, an area of the brain that controls RSA [10,86,122]. The test has been shown to predict BSE infection in cows eight months prior to onset of clinical symptoms of BSE.…”

L’encéphalopathie spongiforme bovine (ESB). Présentation de la vidéo-cassette STIV - AS.FOR.VET.LI

“…Lésions : en l'absence de lésions macroscopiques spécifiques, seule l'observation des lésions histologiques (coupes effectuées au niveau du bulbe) permet de reconnaître cette affection avec certitude [23] ( fig. 3 Une suspicion clinique peut être également confirmée par l'observa tion au miscroscope électronique des filaments associés à la tremblante, ou à l'ESB, ou « scrapie-associated fibrils » (SAF), ou par la mise en évidence de la protéine-prion (western-blot) à partir d'homogénats de cerveau (si celui-ci n'a pas été formolé).…”