Myelin oedema, optic neuropathy and retinopathy in experimental Stypandra imbricata toxicosis

Case report: restored vision after ocular Closantel intoxication and blindness

Background

Closantel is the best-known anti-parasitic medicine for veterinarians, which is contraindicated in humans. After reviewing the literature on ocular toxicity following mistaken usage of Closantel in humans, this report was found as the first complete restoration of visual function after Closantel intoxication. This report could be useful in anticipating the possibility of a further improvement based on a dose-response relationship. An important point of this report is the apparent reversibility of the vision and Electrophysiological parameters after Closantel intoxication and blindness. To conclude, the present case report demonstrates the importance of immediate referral and management in Closantel intoxication to avoid the long-term adverse effects of drug on visual function.

Case presentation

A 47-year-old man mistakenly took about 20 cc of Closantel 5% (15.87 mg/kg). Four hours after mistaken usage of Closantel, he was transferred to the district hospital due to dizziness and nausea. His stomach was washed out immediately after hospital arrival. He was being hospitalized in that hospital for 3 days. Then, he was referred to our clinic due to progressive vision loss. Methylprednisolone acetate 250 mg was injected once on 5th day after taking Closantel. His vision was reducing gradually so low that he could only detect hand motion (HM) on the 14th day after taking Closantel. ERG test was requested. It showed an exclusive reduction in b-wave amplitude under photopic and scotopic conditions. Later, his vision surprisingly improved gradually and his visual acuity was fully restored on the 28th day after the incident. After 3 years, we checked him again. His visual acuity was 20/20 in both eyes and the patient did not have any problem and his ERG report was completely normal.

Conclusions

In low dose of Closantel and immediate referral, ocular toxicity could be resolved.

Inherited and acquired disorders of myelin: The underlying myelin pathology

Remyelination is a major therapeutic goal in human myelin disorders, serving to restore function to demyelinated axons and providing neuroprotection. The target disorders that might be amenable to the promotion of this repair process are diverse and increasing in number. They range primarily from those of genetic, inflammatory to toxic origin. In order to apply remyelinating strategies to these disorders, it is essential to know whether the myelin damage results from a primary attack on myelin or the oligodendrocyte or both, and whether indeed these lead to myelin breakdown and demyelination. In some disorders, myelin sheath abnormalities are prominent but demyelination does not occur. This review explores the range of human and animal disorders where myelin pathology exists and focusses on defining the myelin changes in each and their cause, to help define whether they are targets for myelin repair therapy.

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We reviewed myelin disorders of the CNS in humans and animals.

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Myelin damage results from primary attack on the oligodendrocyte or myelin sheath.

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All major categories of disease can affect CNS myelin.

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Myelin vacuolation is common, yet does not always result in demyelination.

Accidental and experimental Closantel intoxication in Uruguayan sheep

Abstract An outbreak of Closantel intoxication in sheep in Uruguay is described. The outbreak occurred in a group of 1300 weaning lambs treated orally with a 10% solution of Closantel. One hundred forty eight lambs showed clinical signs of intoxication and 14 died. The clinical signs included mydriasis, nystagmus, and negative pupillary reflex, bilateral blindness, bump into objects, and lateral movement of the head. No macroscopic lesions were observed. The histological lesions of the retina were cytoplasmic vacuolization in ganglion cells and in cells of the inner and outer nuclear layers with different degrees of atrophy. Vacuolization and axonal degeneration were observed in the optic nerve, with multifocal areas of fibrosis and infiltration by lymphocytes and Gitter cells. To reproduce the intoxication, four sheep were given two, four and 10 times the therapeutic dose of Closantel (0.1g/kg of BW). Only the animals receiving 10 times the recommended dose showed clinical signs. The histological examination of the lesions in experimental sheep showed similar results to those described in the accidental outbreak, except for the absence of optic nerve fibrosis and inflammation, characterizing an acute phase. Axonal myelin sheaths loss, fibroblasts and collagen fibers were observed in the ultrastructural study of the optic nerve of accidental intoxicated animals. The optic nerve of experimentally intoxicated animals had vacuoles that separated the myelin sheaths of axons. To prevent outbreaks it is suggested to weigh the animals before Closantel administration to avoid errors in dose calculation.

Defeitos congênitos em bovinos da Região Central do Rio Grande do Sul

Foram revisados casos de defeitos congênitos (DCs) diagnosticados em bovinos no Laboratório de Patologia da Universidade Federal de Santa Maria em 1964-2010. Durante o período estudado, foram examinados materiais provenientes da necropsia de 7.132 bovinos e foram encontrados 31 bezerros (0,4%) com DCs, os quais foram classificados em 34 tipos e alocados nos sistemas orgânicos primariamente afetados. Os DCs ocorriam isoladamente (19 [61,3%]) ou afetavam múltiplos sítios anatômicos (15 [28,7%]) com frequência semelhante em ambos os sexos. Como vários terneiros mostraram múltiplos DCs, um total de 53 DCs foi computado. Dos 53 DCs diagnosticados, 15 (28,3%) afetavam o sistema nervoso central (craniósquise [4], abiotrofia cerebelar [2], degeneração esponjosa [2], hidrocefalia [2], meningocele [2], espinha bífida [1], hipoplasia cerebelar [1] e hipomielinogênese [1]); nove (17,0%) afetavam o sistema urogenital (agenesia testicular [1], agenesia vaginal [1], hipoplasia peniana [1], formação de cloaca [1], freemartinismo [1], hamartoma vascular de ovário [1], hipoplasia renal [1], cistos renais [1] e úraco persistente [1]); oito DCs (15,1%) eram primários do sistema musculoesquelético (artrogripose [4], escoliose [1], plagiocefalia, [1] schistosomus reflexus [1] e diprosopia [1]); e outros oito (15,1%) foram alocados no sistema digestivo (palatosquise [3], atresia anal [1], atresia anorretal [1], atresia - anocolônica [1], fístula reto-vaginal [1] e fístula reto-uretral [1]); em cinco ocasiões (9,4%) o DC afetava o sistema cardiovascular (persistência do ducto arterioso [2], persistência do forame oval [2] e defeito do septo ventricular [1]); quatro (7,5%) afetavam o sistema linfático e consistiam de hipoplasia ou aplasia de vasos linfáticos e linfonodos associadas a linfedema. Dois casos (3,4%), de hipotricose foram observados afetando o integumento; um caso (1,9%) de estenose traqueal foi encontrado no sistema respiratório e um caso (1,9%) de bócio envolvia o sistema endócrino. Os resultados indicam que a maioria dos DCs em bovinos na Região Central do Rio Grande do sul é esporádica. No entanto, seu estudo continuado é importante para o estabelecimento de sua etiologia e controle.

Evolução e reversibilidade das lesões neurológicas e cardíacas em ovinos intoxicados experimentalmente por Ateleia glazioviana e Tetrapterys multiglandulosa

Para determinar a reversibilidade das lesões neurológicas e cardíacas nas intoxicações por Ateleia glazioviana e Tetrapterys multiglandulosa, as duas plantas foram administradas por via oral a 3 grupos de quatro ovinos cada. Nos Grupos 1, 2 e 3, quando os animais apresentaram sinais neurológicos de intoxicação com agravamento substancial do quadro clínico e possibilidade de morte, suspendeu-se a administração da planta. O Grupo 4 com dois ovinos foi utilizado como controle. Os ovinos do Grupo 1, que receberam A. glazioviana fresca colhida no outono na dose de 10g/kg por dia durante 6 dias e foram eutanasiados aos 8, 11, 16 e 21 dias após o início do experimento, apresentaram regressão dos sinais nervosos e progressão das lesões cardíacas. Os ovinos do Grupo 2, que receberam a mesma dose de A. glazioviana fresca, colhida na primavera por 8 dias e foram eutanasiados aos 9, 23, 38 e 68 dias apresentaram regressão dos sinais nervosos e não apresentaram lesões cardíacas, sugerindo que a planta é menos tóxica na primavera do que no outono. Os ovinos do Grupo 3, que receberam T. multiglandulosa seca e moída misturada à ração na dose de 10 g/kg durante 11 dias e foram eutanasiados aos 33, 33, 92 e 92 dias, apresentaram regressão dos sinais nervosos e as lesões cardíacas aos 92 dias foram menos severas que aos 33 dias. Esses resultados demonstraram que as lesões do sistema nervoso central são reversíveis após o fim da ingestão. Pelo contrário as lesões cardíacas são progressivas após o fim da ingestão, ocorrendo regressão somente após um período se os animais não apresentarem sinais clínicos e morte. Os resultados deste e de outros trabalhos, analisados em conjunto, comprovam que as lesões do sistema nervoso ocorrem com doses menores e em menor tempo do que as lesões cardíacas. Isto sugere que, em casos espontâneos, sempre que se observam lesões cardíacas estas são precedidas por sinais nervosos e podem ocorrer sinais nervosos sem evidências de lesões cardíacas.

Myelin vacuolation, optic neuropathy and retinal degeneration after closantel overdosage in sheep and in a goat

Toxicity of closantel, a halogenated salicylanilide anthelmintic, is described in 11 sheep and a goat, humanely killed 4-70 days after accidental overdosage. Status spongiosis of the cerebrum and cerebellum was present, its severity decreasing with time after treatment. Ultrastructurally, vacuoles in the cerebral white matter were seen to be intramyelinic due to splitting of myelin lamellae at the intraperiod lines, indicating myelin oedema. In the optic nerves, Wallerian degeneration and eventual fibrosis and atrophy of the nerves followed myelin vacuolation. Lesions in the optic nerves were particularly advanced in the intracanalicular portion, indicating a compressive neuropathy within the optic canal. Acute retinal lesions consisted of papilloedema, necrosis of the outer retinal layers (especially the photoreceptor layer), and retinal separation in tapetal and non-tapetal areas. In more chronic cases, the outer nuclear layer was diffusely attenuated and generally reduced to a single row of cells.

Degeneração esponjosa no sistema nervoso central de bezerros da raça Sindhi

Degeneração esponjosa (status spongiosus) agrupa várias alterações histológicas caracterizadas pela formação de vacúolos no neurópilo em diferentes regiões do sistema nervoso central (SNC). Essa vacuolização pode ser por edema intramielínico, como na doença da urina com odor de xarope de bordo (maple syrup urine disease) e algumas doenças tóxicas, ou por edema de astrócitos, como na citrulinemia. Este trabalho descreve degeneração esponjosa do SNC em dois bezerros, um macho e uma fêmea, da raça Sindhi. Ambos são filhos de um mesmo touro, de um rebanho que apresentava alto grau de consangüinidade. Uma fêmea nasceu normal e aos 2 meses apresentou sinais nervosos progressivos. Um macho apresentou sinais nervosos progressivos desde o nascimento. Os dois foram eutanasiados aos 4 meses de idade com acentuadas alterações do sistema nervoso central. Na necropsia o fígado de bezerro macho estava pálido. Histologicamente havia, em ambos os bezerros, discreta a acentuada vacuolização difusa do SNC, sendo mais acentuada nas camadas profundas do córtex cerebral, cápsula interna, substância branca da medula cerebelar, tronco encefálico e substância cinzenta da medula. No fígado dos dois animais havia degeneração gordurosa nos hepatócitos da região centrolobular. Na microscopia eletrônica observou-se que o status spongiosus era devido a edema astrocitário. Sugere-se que a doença é causada por um erro metabólico hereditário, diferente da doença da urina com odor de xarope de bordo.

Epizootic vacuolar myelinopathy of the central nervous system of bald eagles (Haliaeetus leucocephalus) and American coots (Fulica americana)

Unprecedented mortality occurred in bald eagles (Haliaeetus leucocephalus) at DeGray Lake, Arkansas, during the winters of 1994-1995 and 1996-1997. The first eagles were found dead during November, soon after arrival from fall migration, and deaths continued into January during both episodes. In total, 29 eagles died at or near DeGray Lake in the winter of 1994-1995 and 26 died in the winter of 1996-1997; no eagle mortality was noted during the same months of the intervening winter or in the earlier history of the lake. During the mortality events, sick eagles were observed overflying perches or colliding with rock walls. Signs of incoordination and limb paresis were also observed in American coots (Fulica americana) during the episodes of eagle mortality, but mortality in coots was minimal. No consistent abnormalities were seen on gross necropsy of either species. No microscopic findings in organs other than the central nervous system (CNS) could explain the cause of death. By light microscopy, all 26 eagles examined and 62/77 (81%) coots had striking, diffuse, spongy degeneration of the white matter of the CNS. Vacuolation occurred in all myelinated CNS tissue, including the cerebellar folia and medulla oblongata, but was most prominent in the optic tectum. In the spinal cord, vacuoles were concentrated near the gray matter, and occasional swollen axons were seen. Vacuoles were uniformly present in optic nerves but were not evident in the retina or peripheral or autonomic nerves. Cellular inflammatory response to the lesion was distinctly lacking. Vacuoles were 8-50 microns in diameter and occurred individually, in clusters, or in rows. In sections stained by luxol fast blue/periodic acid-Schiff stain, the vacuoles were delimited and transected by myelin strands. Transmission electron microscopy revealed intramyelinic vacuoles formed in the myelin sheaths by splitting of one or more myelin lamellae at the intraperiodic line. This lesion is characteristic of toxicity from hexachlorophene, triethyltin, bromethalin, isonicotinic acid hydrazide, and certain exotic plant toxins; however, despite exhaustive testing, no etiology was determined for the DeGray Lake mortality events. This is the first report of vacuolar myelinopathy associated with spontaneous mortality in wild birds.

Status spongiosis, optic neuropathy, and retinal degeneration in Helichrysum argyrosphaerum poisoning in sheep and a goat

Lesions of natural Helichrysum argyrosphaerum poisoning were studied in eight sheep and one goat. Light microscopic examination revealed widespread, bilaterally symmetrical status spongiosis of the white matter of the brain consistently present in the subependymal area adjacent to the lateral ventricles, cerebellar peduncles, and brain stem in all animals. In three animals, the ultrastructural finding of intramyelinic vacuolation due to splitting of the myelin lamellae at the intraperiod lines indicated myelin edema. There was also mild distension of perivascular and extracellular spaces in the severely affected areas. Significant changes were absent in neurons, glial cells, axons, or blood vessel walls. Myelin edema associated with degeneration and loss of axons and myelin and astrocytic gliosis was present in the intraorbital and intracranial portions of the optic nerves. In the intracanalicular portions of the nerves in three animals that were studied, more chronic lesions consisting of fibrosis and atrophy of the nerve suggested that the optic neuropathy follows compression of the nerve in the optic canal as a result of myelin edema. The toxic principle of the plant also caused a degenerative retinopathy in five animals. The essential histopathologic change was degeneration and loss of the photoreceptor outer segments predominantly in the nontapetal retina. These retinal lesions were associated with hyperplasia and hypertrophy and with migration of the pigmented epithelium, focal retinal separation, and depletion and loss of the nuclear layers.

The toxic and abortifacient effects of ponderosa pine

Ponderosa pine needles cause abortion and a poorly described toxicosis when eaten by cattle. In previous trials, the abortifacient compound of pine needles was identified as isocupressic acid. At abortifacient doses, isocupressic acid caused no other toxicosis. However, other pine needle fractions, similar in composition to several commercially available rosin products, caused no abortion but were very toxic. The purpose of this study was to describe the toxicoses of ponderosa pine, compare its toxicity with other rosin and related pine products, and identify the toxin. Four groups of three pregnant beef cows each were treated with either ponderosa pine tips, rosin gum, dehydroabietic acid, or ground alfalfa. The cows treated with pine tips aborted, had retained placentas with endometritis, and developed both renal and neurologic lesions. The cattle treated with rosin gum or dehydroabietic acid did not abort but developed similar signs and lesions of intoxication. Clinical signs of intoxication included anorexia, mild rumen acidosis, dyspnea, paresis progressing to paralysis, and death. Clinical biochemical results, suggestive of renal, hepatic, and muscular disease, included azotemia, hypercreatinemia, hyperphosphatemia, proteinuria, and marked elevations of various serum enzymes. Histologically, all poisoned animals had nephrosis, vacuolation of basal ganglia neuropil with patchy perivascular and myelinic edema, and skeletal myonecrosis. The alfalfa-treated controls were normal. These findings suggest that ponderosa pine needles and tips are both abortifacient and toxic. Because the lesions caused by pine tips, rosin gum, and dehydroabietic acid are similar, toxicosis is most likely due to the diterpene abietane acids, common in all three.

Vitamin A deficiency and connective tissues: a new etiological approach

A unifying concept, that the impairment of connectives tissue, owing to the effect of immigrant cells, is at the basis of the pathogenesis of Vitamin A deficiency has been considered. Changes in various tissues and organs have been reviewed in the light of the recent discoveries in the field of histology (1). An effort has been made to link the various symptoms of Vitamin A deficiency to those related to other pathologies where connective tissues are involved, and to suggest a plan for research to be undertaken to achieve a better knowledge of the etiology of Vitamin A deficiency.

Ultrastructural findings in maple syrup urine disease in Poll Hereford calves

Ultrastructural findings in the nervous systems of two Poll Hereford calves affected with maple syrup urine disease or branched chain ketoacid decarboxylase deficiency are described. The calves were affected within 2 days of birth with a severe generalised central nervous system (CNS) disorder characterised by dullness and weakness, progressing to recumbency and opisthotonus. The urine had an odour of burnt sugar. Analysis of plasma and cerebrospinal fluid demonstrated significantly elevated levels of the branched chain amino acids leucine, isoleucine and valine. Status spongiosus affecting mainly the white matter was recorded at microscopic examination of the CNS, with ultrastructural examination confirming the presence of intramyelinic vacuole formation, suggesting myelin oedema.

Stypandra imbricata ("blindgrass") toxicosis in goats and sheep - clinical and pathologic findings in 4 field cases

Two goats and 2 sheep from field outbreaks of Stypandra imbricata toxicosis had severe lesions in the retina, optic nerves and white matter of the central nervous system. Clinical, ophthalmoscopic, fluorescein angiographic, electroretinographic and histologic atrophy, necrosis and degeneration of axons in the optic nerves and optic tracts and status spongiosus of cerebral white matter.