Clinical, pathological, and molecular features of classical and L-type atypical-BSE in goats

<div><p>Monitoring of small ruminants for transmissible spongiform encephalopathies (TSEs) has recently become more relevant after two natural scrapie suspected cases of goats were found to be positive for classical BSE (C-BSE). C-BSE probably established itself in this species unrecognized, undermining disease control measures. This opens the possibility that TSEs in goats may remain an animal source for human prion diseases. Currently, there are no data regarding the natural presence of the atypical BSE in caprines. Here we report that C-BSE and L-type atypical BSE (L-BSE) isolates from bovine species are intracerebrally transmissible to goats, with a 100% attack rate and a significantly shorter incubation period and survival time after C-BSE than after L-BSE experimental infection, suggesting a lower species barrier for classical agentin goat. All animals showed nearly the same clinical features of disease characterized by skin lesions, including broken hair and alopecia, and abnormal mental status. Histology and immunohistochemistry showed several differences between C-BSE and L-BSE infection, allowing discrimination between the two different strains. The lymphoreticular involvement we observed in the C-BSE positive goats argues in favour of a peripheral distribution of PrPSc similar to classical scrapie. Western blot and other currently approved screening tests detected both strains in the goats and were able to classify negative control animals. These data demonstrate that active surveillance of small ruminants, as applied to fallen stock and/or healthy slaughter populations in European countries, is able to correctly identify and classify classical and L-BSE and ultimately protect public health.</p></div

Haematoxylin and eosin.

<p>A: Frontal cortex of C-BSE (10X); B: Frontal cortex of L-BSE (10X); C: Dorsal nucleus of vagus nerve, brainstem of C-BSE (10X); D: Dorsal nucleus of vagus nerve, brainstem of L-BSE (10X). The single image shows one animal (81556 for C-BSE and 69540 for L-BSE) representative of all animals in the group. Scale bar: 100 μm.</p

Non-quantitative diagram of neuroanatomical distribution of PrP immunolabelling in L-BSE group.

<p>This distribution refers to one animal (69540) representative of all animals in the group. A: Telencephalon; B: Diencephalon; C: Mesencephalon; D: Pons; E: Cerebellum; F: Brainstem.</p

Kaplan–Meier survival curves for survival times.

<p>Kaplan–Meier survival curves for survival times.</p

Survival time (SV) and incubation period (IP) in C-BSE and L-BSE infected goats and mean SV in negative goats.

<p>Survival time (SV) and incubation period (IP) in C-BSE and L-BSE infected goats and mean SV in negative goats.</p

Western blot analysis of proteinase K-treated homogenates from brainstems of goats intracerebrally inoculated with C-BSE.

<p>I: C- BSE (16819/06) isolate used for <i>inoculum</i>; lanes 1–5: inoculated goats; gs: goat with natural classical scrapie. MW: molecular size markers. Membranes were probed with three different monoclonal antibodies: P4 (A), 6H4 (B), and SAF84 (C). Panel D shows the proteinase K-treated homogenates treated with enzymatic deglycosylation (PNGase) and detected with mAb SAF84.</p

Antibodies to PrP used for IHC and WB analysis, indicating the corresponding epitopes.

<p>Antibodies to PrP used for IHC and WB analysis, indicating the corresponding epitopes.</p

Mean values of vacuolar lesion profiles.

<p>Square = BSE i.c. goats; rhombus = L-BSE i.c. goats (Brain areas, Medulla (at obex): 1 Dorsal nucleus of the vagus nerve, 2 Nucleus of the hypoglossal nerve, 3 Reticular formation, 4 Midline Raphe, 5 Accessory cuneate nucleus, 6 Olivary nuclei; Rostral medulla: 7 Vestibular nuclear complex, 8 Cochlear nucleus, 9 Nucleus of the spinal tract of the trigeminal nerve, 10 Midline raphe; Cerebellar vermis: 11 Nodulus±granular layer, 12 Nodulus±molecular layer; Midbrain: 13 Central grey matter, 14 Red nucleus, 15 Substantia nigra, 16 Lateral geniculate nucleus; Thalamus: 17 Dorsomedial thalamic nucleus, 18 Ventral thalamic nuclei, 19 Area hypothalamica; Frontal: 20 Caudate nucleus, 21 Nucleus accumbens, 22 Frontal cortex).X-axis: brain areas; Y-axis: mean vacuolation score with error bars (standard deviation).</p

Immunohistochemistry.

<p>Labelling with F99/97.6.1, with DAB used as chromogen; the immunoreactivity is brown in colour. A: Brainstem, reticular formation, C-BSE (10X); B: Brainstem, reticular formation, L-BSE (10X); C: Cerebellum, C-BSE (10X), *: molecular layer; D: Cerebellum, L-BSE (10X), *:molecular layer; E: Midbrain, central grey matter, C-BSE (10X); F: Midbrain, substantia nigra, L-BSE (10X); Scale bar: 100 μm. G: Submandibular lymph node, C-BSE (40X); H: Ileocecal valve, C-BSE (40X); Scale bar: 25 μm.</p

Western blot analysis of proteinase K-treated homogenates from brainstems of goats intracerebrally inoculated with L-BSE.

<p>I: L-BSE isolate (141387/02) used for <i>inoculum</i>; lanes 1–6: inoculated goats; gs: goat with natural classical scrapie. MW: molecular size markers. Membranes were probed with three different monoclonal antibodies: P4 (A), 6H4 (B), and SAF84 (C). Panel D shows the proteinase K-treated homogenates treated with enzymatic deglycosylation (PNGase) and detected with mAb SAF84. WB analyses of tissue samples from the experimentally challenged goats showed the presence of PrPSc, with an electrophoretic pattern characterized by three bands corresponding to the di-, mono-, and un-glycosylated forms.</p