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IN response to your call for feedback on whether there should be tougher maximum penalties for animal cruelty ( VR , February 25, 2017, vol 180, p 187), I am entirely in favour of a substantial increase in …

A country boy who became, and remained, a countryman at heart. He was fascinated by diseases of wildlife and collaborated with others to publish widely on the topic.

Prion protein (PrP) immunohistochemical staining of the brains of common marmosets (Callithrix jacchus) with experimental transmissible spongiform encephalopathy is described. The monkeys (n = 17) had been injected, intracerebrally, 17-49 months previously with homogenates of brain tissue taken post mortem from a cow with BSE (n = 2 monkeys), a sheep with natural scrapie (n = 2 monkeys), human cases of growth hormone related Creutzfeldt-Jakob disease (CJD) (n = 2 monkeys), sporadic CJD (n = 5 monkeys), or Gerstmann-Sträussler-Scheinker disease (GSS) (n = 4 monkeys), or from monkeys with spongiform encephalopathy resulting from injection with brain tissue from these last two cases (n = 1 monkey from each case). Only diffuse PrP-staining was seen in monkeys injected with CJD-material whereas more aggregated deposits of PrP were seen in monkeys injected with BSE-, scrapie--and GSS-brain tissue. There were no patterns of staining specific to the brains injected with BSE-material that could be used to identify the origin of that inoculum. BSE--and scrapie-injected monkey brains could be distinguished from each other because in BSE-injected monkey brain the spongiform vacuolation was largely confined to subcortical structures whereas in scrapie-injected monkey brain the spongiform vacuolation was also prominent in the neocortex. The patterns of PrP deposition differed markedly between those seen in monkey brains injected with BSE-material or CJD-material, but the patterns of PrP staining seen in monkey brains injected with BSE-material were also seen in monkey brains injected with scrapie--or GSS-material. Overall there was a correlation between the length of the incubation period and the amount of aggregated PrP-staining, but no correlation between the neuropathological picture and the clinical presentation of neurological signs.

To determine whether the aetiological agent of bovine spongiform encephalopathy (BSE) is pathogenic for mink, standard dark mink were inoculated with coded homogenates of bovine brain from the U.K. Two homogenates were from cows affected with BSE. The third was from a cow that came from a farm with no history of having had BSE or having been fed ruminant-derived, rendered by-products, the proposed vehicle for introduction of the BSE agent. Each homogenate was inoculated intracerebrally into separate groups of mink and a pool of the three was fed to a fourth group. Signs of neurological disease appeared in mink an average of 12 months after intracerebral inoculation and 15 months after feeding. Decreased appetite, lethargy and mild to moderate pelvic limb ataxia were the predominant clinical signs, quite unlike the classic clinical picture of transmissible mink encephalopathy (TME). Microscopic changes in brain sections of most affected mink were those of a scrapie-like spongiform encephalopathy. Vacuolar change in grey matter neuropil was accompanied by prominent astrocytosis. Varying greatly in severity from one mink to another, the degenerative changes occurred in the cerebral cortex, dorsolateral gyri of the frontal lobe, corpus striatum, diencephalon and brainstem. Although resembling TME, the encephalopathy was distinguishable from it by less extensive changes in the cerebral cortex, by more severe changes in the caudal brainstem and by sparing of the hippocampus. The results of this study extend the experimental host range of the BSE agent and demonstrate for the first time the experimental oral infection of mink with a transmissible spongiform encephalopathy agent from a naturally infected ruminant species.

A chronic progressive neurodegeneration, called hereditary porcine neuronal system degeneration (HPNSD), was recognized in a swine herd in Devon, England. Adult pigs that were presumed carriers of the dominantly inherited trait for HPNSD were transferred from England, where a breeding colony was maintained for 9 years, to the Wyoming State Veterinary Laboratory (WSVL) for study. Two litters of affected piglets were born to 2 carrier sows at the WSVL. Clinical signs of muscular tremors, paresis, or ataxia developed at 12–59 days of age in 4 of 6 liveborn pigs. Three other pigs were stillborn. In the 4 affected livebom pigs, clinical signs progressed and included symmetrical (3 pigs) or asymmetrical (1 pig) posterior paresis, bilateral knuckling of metatarsal-phalangeal or carpal joints, poor exercise tolerance, and in 1 pig, marked hind limb hypermetria. A 34-kg gilt exhibiting clinical signs of muscular tremors and posterior paresis and clinical signs for 22 days was euthanized and examined postmortem at 83 days of age. Apart from decubitus ulcers, gross lesions were absent. Microscopically, perikaryal vacuolation and osmiophilic lipid droplets were observed in atrophic alpha motor neurons in the spinal cord. There was axonal (Wallerian) degeneration in sulcomarginal and dorsal spinocerebellar tracts. Axonal degeneration also involved ventral but not dorsal spinal nerve roots, and was present in eight peripheral nerves sampled for histopathology. Changes in skeletal muscles were consistent with denervation atrophy and were most pronounced in M. tibialis cranialis of the 6 muscles sampled. Immunohistochemical staining of spinal cord for phosphorylated and nonphosphorylated neurofilaments did not reveal abnormal patterns, unlike some well-characterized inherited motor neuron diseases in other species.

The efficacy of three pretreatment techniques for the detection of prion protein (PrP) in formalin-fixed, paraffin-embedded bovine spongiform encephalopathy (BSE)--affected brain tissue were compared using automated image analysis. The most abundant immunostaining was in the form of particulate expression observed in sections pretreated with hydrated autoclaving for 30 min. Considerably less immunostaining occurred in sections pretreated with formic acid and no specific particulate immunostaining was detected in sections pretreated with hydrolytic autoclaving. Hydrated autoclaving pretreatment of sections prior to PrP immunolabelling gives visualisation of widespread sites of abnormal PrP deposition in the brain, allowing detailed study of the form and distribution of the protein in routinely fixed bovine central nervous system affected with BSE.

Transmission from four cases of bovine spongiform encephalopathy (BSE) to mice resulted in neurological disease in 100% of recipient animals, after incubation periods of between 265 and 700 days post-injection. The results from the four cases were very similar to one another. There were major differences in the incubation period between the four inbred strains of mice tested, and even between strains of the same Sinc genotype, and the incubation periods of Sinc heterozygote mice were much longer than those for any of the inbred strains. Transmission from a case of natural scrapie differed in two important respects: there were no differences in the incubation period between mouse strains of the same Sinc genotype, and that of the heterozygotes was between those of the Sinc homozygotic parental strains. The distribution of vacuolar degeneration in the brains of mice infected with scrapie also differed from those infected with the BSE isolates. Transmission was also achieved from formol-fixed BSE brain. These results show that the same strain of agent caused disease in the BSE cases, and that the relationship of BSE to scrapie in sheep is unclear.

Bovine spongiform encephalopathy (BSE), defined originally from its characteristic neuropathology, retains a place of particular interest in the scrapie-like or prion disease group, presenting uniquely an example of such diseases occurring as a nationwide food-borne epidemic in Great Britain. Comprehensive monitoring of the epidemic, both pathologically and epidemiologically, has facilitated our present understanding of the disease. BSE presents the classical neuropathological features of the transmissible spongiform encephalopathies. Although particularly similar to natural scrapie of sheep, BSE has, unlike scrapie, a stereotypic lesion profile from which it has been concluded that host and agent factors, including probably the strain of agent, which influence the profile, are constant in this disease. Neuronal loss in BSE may make an important but hitherto inapparent contribution to functional deficits. Preliminary ultrastructural studies have confirmed light microscopic features of brain changes in BSE but have as yet not established significant new findings. Immunohistochemical studies of PrP accumulation reveal distinctive forms and distributions of immunolabelling, confirming features reported previously in experimental models of scrapie, including perineuronal and perineuritic “synapse-like” reactivity. The histopathological diagnosis of BSE, validated on a single section of the medulla for the statutory diagnosis of large numbers of cases, is supplemented where necessary by fibril (SAF) examination which performs similarly to the histological diagnosis in the majority of cases. Epidemiological studies of BSE have supported the pathological findings that there is no detectable variation in susceptibility within the cattle population. The detailed monitoring of the epidemic has revealed the expected effects on the incidence as a result of statutory measures intended to prevent food-borne exposure after July 1988. The main effect has been a reduction in the national incidence during 1993 which has been continued into 1994. Analytical studies have not revealed any means of transmission, other than the food-borne source, capable of maintaining the epidemic in Great Britain. An international comparison of risk factors for the occurrence of BSE indicates that an epidemic of similar magnitude outside the British Isles is unlikely.

A statistical comparison was made between the results of the statutory neurohistopathological method for the post mortem diagnosis of bovine spongiform encephalopathy (BSE) and the detection of abnormal brain fibrils (SAF). A total of 773 suspect cases was examined by both methods; it comprised 531 animals born before the feeding of ruminant-derived protein to ruminant species was prohibited and 242 born after the ban. The relative sensitivities and specificities of the methods were calculated for the diagnosis of clinically suspected BSE. The agreement between the results of the methods was excellent for 331 of the cases born before the ban and for all the cases born after it. In these cases the samples were not autolysed. For the 200 cases in which autolysis was recorded there was poor agreement between the diagnostic methods and this was attributed to an apparently reduced specificity of the histopathological diagnosis in the autolysed material. Despite the potentially greater specificity of fibril detection in the diagnosis of scrapie-like disease, this study indicates that a reliance on fibril detection alone may result in some false negative diagnoses, probably owing to the inadequate sampling of the tissues.

The ultrastructural features of a recently described inherited lower motor neuron disease were studied in 5 affected pigs. Clinical signs comprised progressive ataxia and paresis of variable severity. Affected pigs, 6, 7, 15, 15, and 19 weeks of age, and 2 unrelated healthy pigs, 9 and 15 weeks of age, were anesthetized and their tissues were fixed by whole body perfusion with mixed aldehydes. From 1 or more affected pigs, samples of cervical and lumbar spinal ventral horn, lateral and ventral spinal columns, dorsal and ventral lumbar spinal nerve roots, 2 peripheral nerves (Nn. phrenicus and fibularis communis), and 2 skeletal muscles (Mm. diaphragma and tibialis cranialis) were examined ultrastructurally. There was widespread degeneration of myelinated axons in peripheral nerves and in lateral and ventral columns of lumbar and cervical segments of spinal cord. Axonal degeneration was present in ventral spinal nerve roots and was absent in dorsal spinal nerve roots sampled at the same lumbar levels. Unmyelinated axons in peripheral nerves and spinal nerve roots were unaffected. In 4 of 5 affected pigs, there were atrophic alpha motor neurons in cervical spinal cord that contained dense, round osmiophilic perikaryal inclusions up to 4 μm in diameter and round swollen mitochondria. Axonal regeneration was present in N. phrenicus of the 19-week-old affected pig that had clinical signs of longest duration (10 weeks). There was no morphologic evidence of axonal degeneration or spinal neuronal atrophy in either control pig. The ultrastructural features of this motor neuron disease distinguish it from other reported progressive spinal neuropathies of pigs.

Two young male common marmosets (Callithrix jacchus) were injected intracerebrally and intraperitoneally with a crude brain homogenate prepared from a cow with bovine spongiform encephalopathy (BSE). Two other marmosets were similarly injected with brain homogenate from a sheep with natural scrapie. The two animals injected with scrapie material developed neurological signs 38 and 42 months after injection and the two animals injected with BSE material developed neurological signs after 46 and 47 months. Post mortem examination of the brains revealed spongiform encephalopathy especially in the basal nuclei and diencephalon of all the animals and, in addition, involvement of the cerebral cortex of the marmosets injected with scrapie material. The experiment extends the host range of experimental BSE to include a primate species.

Bovine spongiform encephalopathy (BSE) is a transmissible neurodegenerative disease. Six brain regions from 11 cattle were examined for the presence of the abnormal isoform of the prion protein (PrPBSE). The highest concentrations of PrPBSE were found in the brain stem, where the greatest degree of spongiform change was observed. Molecular cloning of the bovine PrP gene showed that it encodes a protein of 256 or 264 amino acids with five or six Gly:Pro-rich octarepeats, respectively, in contrast to all other mammalian PrP genes, which encode only five octarepeats. The bovine PrP gene is single copy, and the entire open-reading frame lies within a single exon. Since the transmission of prions across species seems to be restricted by differences in PrP sequence, the high degree of homology between sheep and bovine PrP (98%) correlates with the proposed cause of BSE.

A captive adult puma developed ataxia, a hypermetric gait and whole body tremor. The signs progressed over a period of six weeks. Histopathological examination following euthanasia demonstrated spongiform encephalopathy, gliosis and mild non-suppurative meningoencephalitis. Immunostaining with a polyclonal antiserum revealed prion protein (PrP) associated with these changes in sections of cervical spinal cord and medulla. This is the first confirmed case of a scrapie-like spongiform encephalopathy described in a non-domestic cat in the United Kingdom.

The effect of autolysis on the electron microscopic detection of the characteristic abnormal fibrils, originally called ‘scrapie-associated fibrils’, was investigated in four different areas of the central nervous system ( cns ) from 10 clinically suspect bse cattle after postmortem delay and compared with the histopathological diagnosis. The tissues for fibril detection were subjected to controlled incubations to simulate autolysis. Fibril detection in all areas sampled from nine animals in which bse was confirmed by histopathology was not affected by combined post mortem delays and specific controlled treatments. Detection of fibrils from the cervical spinal cord was no less sensitive than from brain areas. Fibrils were not detected in the one suspect case in which histopathology did not reveal lesions of bse . The study confirms that fibril detection is of diagnostic value in bse when post mortem autolysis renders cns material unsuitable for histopathology.

Naturally occurring transmissible spongiform encephalopathies have been recognised in sheep, man, mink, captive deer and cattle. Recently a similar disease was reported in a domestic cat. This paper describes the clinical and pathological findings in five cats with similar signs, including further observations on the original case. All the cats had a progressive, neurological disease involving locomotor disturbances, abnormal behaviour and, in most cases, altered sensory responses. Histopathological examination of the central nervous system revealed changes pathognomonic of the scrapie-like encephalopathies, including widespread vacuolation of the grey matter neuropil, vacuolation of neuronal perikarya and an astrocytic reaction.

The occurrence of bovine spongiform encephalopathy (BSE), recognition that it is a new scrapie-like disease epidemic in domestic cattle in the United Kingdom and concern of a remote zoonotic potential has, in four years, produced a plethora of documented information. While much of this information has been communicated outwith the scientific literature, this review attempts to summarise, from a neuropathological viewpoint, the main findings to emerge. The initial studies established the nosological homology of BSE with the subacute spongiform encephalopathies or "prion" diseases of animals and man. Epidemiological data are consistent with an extended common source epidemic originating from an abrupt change, commencing in 1981-82, in the exposure of domestic cattle to a scrapie-like agent in meat and bone meal incorporated into commercial animal feedstuffs. It is currently proposed that the method of production of meat and bone meal has contributed vital factors to the change in exposure. Invariability of the distribution pattern of vacuolar pathology in the natural disease and on primary transmission to cattle suggests a uniformity of the pathogenesis of BSE. Studies in mice suggest uniformity also of the biological properties of different BSE isolates but indicate that the properties differ from those of sheep scrapie isolates. Human health risks, although perceived to be negligible, have been addressed by various strategies including statutory measures and long term monitoring.

A 4-year-old Canadian holstein bull developed the spastic syndrome, an episodic but progressive disorder causing pelvic limb muscular spasms. A post-mortem study, including morphometry of skeletal muscles and teased peripheral nerve fibers of the pelvic limb, revealed mild type II skeletal muscle fiber atrophy and minimal, focal segmental demyelination with remyelination, and axonal degeneration in peripheral nerves. Such alterations are probably incidental or age-associated. Idiopathic muscular cramps is the most probable explanation of the clinical disease and is consistent with the absence of significant morphologic pathologic lesions.

A landrace boar with a previous history of siring progeny with cystic kidneys was bred to five unrelated large white sows. Thirty-eight of 61 progeny (62 per cent) were affected with renal cysts. This incidence does not differ significantly from that expected with autosomal dominant inheritance. Three of the dams and the boar were found at post mortem examination to have renal cysts. The number of cysts may be determined by polygenic inheritance. Study of the pathology of the cysts in one-day-old, 25- to 32-day-old and 370-day-old progeny indicated a complex pathogenesis including probable recruitment to the cyst population throughout the period studied. The syndrome studied did not resemble previously described polycystic syndromes of the pig nor was it closely comparable to any of the well described polycystic syndromes and renal cystic disorders of man.

Experimental lead encephalopathy of calves. Histological observations on the nature and distribution of the lesions Neurological signs were induced in four calves by the daily administration of 20 mg/kg body weight lead acetate. The time of onset and duration of symptoms varied, and the severity progressed to an acute neurological episode in three calves. Histological lesions in the brains of three calves consisted of focal vacuolation of the neuropil, neuronal necrosis and changes in capillary walls. These changes occurred in the cerebral cortex and in certain grey centres of the brain stem. The encephalopathy was associated with elevated blood and tissue lead levels, but could not be correlated with pathological effects in other organs. The nature of the lesions suggests a basic change in transport mechanisms between the blood and brain.

During the past two years, more than 1,000 cases of a neurological disorder of cattle, bovine spongiform encephalopathy (BSE), have been confirmed from farms throughout Great Britain. The neurological signs and brain pathology of BSE resemble those produced in other species by the pathogens of scrapie and related disorders. The discovery of fibrils similar to scrapie-associated fibrils in detergent extracts o BSE-affected brain supported the clinical and pathological diagnosis of the disease, but has been controversial. Scrapie-associated fibrils are found in brain extracts of all species affected by scrapie and diseases caused by related pathogens. They are pathological aggregates of a neuronal membrane protein termed PrP and a protease-resistant form of PrP is a molecular marker of scrapie-associated fibrils. In this report, we show the major protein of BSE fibrils is the bovine homologue of PrP as judged by its size, protease resistance, immunoreactivity, lectin binding and partial N-terminal protein sequence. This confirms that BSE is a scrapie-like disease.

Clinical and pathological observations of a naturally occurring disease in a British wild otter (Lutra lutra) are reported. Systemic lymphoreticular proliferative changes with plasmacytosis, glomerulonephritis, arteritis and biliary hyperplasia closely resembled the pathological changes in Aleutian disease of mink (Mustela vison). Feral mink provided a possible source of infection.

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.

Multifocal ischaemic encephalomyelopathy associated with fibrocartilaginous emboli in the lamb Multifocal, arterial, fibrocartilaginous embolism of the cervical spinal cord, medulla oblongata and cerebellum is described in a neonatal lamb. The emboli contained mucosubstances which, by the Alcian blue critical electrolyte concentration method, were identified as mainly keratan sulphate. This composition indicates the probable origin of emboli from the nucleus pulposus of intervertebral discs. Possible modes of entry of such material into the spinal cord vasculature are reviewed and a mechanism proposed to explain the localization of emboli in spinal cord, brain stem and cerebellar arteries in this case.

A familial progressive muscular weakness is described in a herd of pietrain pigs. The onset of disease was at two to three weeks of age taking the form of a muscular tremor when the piglets were standing. An impaired gait followed and by 12 weeks of age the pigs had become permanently recumbent. The observed incidence of the syndrome and the breeding data available were consistent with an autosomal recessive inheritance of the condition.

An abattoir investigation into kidney condemnations due to renal cysts in pork pigs from one producer showed a prevalence of 47.5 per cent. Affected pigs were the progeny of a landrace boar. Similar cysts found in a small sample of day-old piglets sired by the same boar indicated a congenital origin. A marked variation in size and frequency of cysts in the kidneys of slaughtered pigs was seen, some resembling the severity of polycystic kidneys. Histologically cysts appeared to be of tubular origin. The prevalence of affected pigs in slaughter groups from the single herd could be genetically determined. If this were so the data would be consistent with autosomal dominant inheritance. A breeding experiment to examine this hypothesis is in progress.