Closantel toxicity in a pregnant ewe at mid gestation: the pathological evaluation of the ewe and lamb nine months later

Hannon, Fergus Patrick; Ellis, Kathryn; Guevar, Julien; Marchesi, Francesco; Geraghty, Timothy; Leach, Joshua

doi:10.1136/vetreccr-2014-000113

Cited by 4 publications

(5 citation statements)

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“…The toxicities were due to bracken poisoning or Closantel toxicity. Both toxicities to the nervous system have been well reported in sheep 27–29 . In contrast, traumatic aetiologies were only seen in cattle.…”

Section: Discussionmentioning

confidence: 98%

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Ruminant neurological disease: a retrospective cohort study

et al. 2017

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Between January 2006 and June 2016, 96 ruminants with neurological signs were donated to the Scottish Centre for Production Animal Health and Food Safety (SCPAHFS), University of Glasgow, by veterinarians in the field representing 5.4 per cent of all submissions. Forty-seven different neurological presenting signs were reported with 79 per cent of the donated patients presenting with abnormal gait. All cases presenting with abnormalities in more than 4 out of 10 neurological categories died or were euthanased on welfare grounds. Calves were significantly more likely to present with neurological disorders than adult cattle compared with the proportion of calves: cows in the Scottish cattle population and total case population donated to SCPAHFS. Lesions were most commonly localised to the spinal cord in sheep 47 per cent (16), the peripheral nervous system in cattle 45 per cent (28) and to the brain in the overall population 41 per cent (39). The most common aetiology of neurological pathologies observed was infectious or inflammatory 28 per cent (27). Definitive diagnoses could be reached in 84 per cent (81) of patients. When postmortem reports were available, they produced a diagnosis in 70 per cent (52) of cases and contradicted clinical diagnoses in 38 per cent (26) of cases. The most frequently diagnosed conditions in ruminants over the 10 years were spastic paresis, vertebral osteomyelitis and listeriosis.

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Section: Discussionmentioning

confidence: 98%

“…Both toxicities to the nervous system have been well reported in sheep. [27][28][29] In contrast, traumatic aetiologies were only seen in cattle. Vertebral fractures or nerve paralysis accounted for all the trauma cases.…”

Section: Discussionmentioning

confidence: 99%

Ruminant neurological disease: a retrospective cohort study

et al. 2017

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“…The mechanism of closantel poisoning remains poorly understood in sheep; nevertheless, some previous studies suggest that ocular lesions are associated with optic neuropathy following retinal edema [10,11,17]. Edema leads to the degeneration of ganglia cells, reflecting in the toxic effect on neurons.…”

Section: Discussionmentioning

confidence: 99%

“…Moreover, axonal lesions in the optic nerve may occur [17,19]. Other mechanisms which may be involved in lesion development include optic nerve compression within the bone structures of the optic canal and the rupture of cells and compacted cell membrane layers, these are associated with retinopathy, myelin edema and white matter vacuolation [11,16].…”

Section: Discussionmentioning

confidence: 99%

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Accidental Closantel Poisoning in Sheep in the State of Rio Grande do Sul - Brazil

Pohl

Lorenzett

Cecco

et al. 2020

Acta Scientiae. Vet.

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Background: Verminosis is one of the major health problems in sheep flocks, and is one of the main causes of death in sheep worldwide. Closantel is an antiparasitic drug commonly used in sheep; however, its safety margin is narrow, and this drug may induce intoxication in animals submitted to high doses. Lesions occur mainly in the eyes, and are characterized by edema and compression of the optic nerve, retinopathy, and severe degeneration of ganglia cells. Clinical signs are pupil dilation, which often lead to permanent blindness. This work aims to report an outbreak of sheep mortality due to closantel intoxication, associated with inadequate anthelmintic administration practices.Case: An on-site visit was conducted to a sheep farm, located in the municipality of Osório, Rio Grande do Sul (RS), in which high mortality was reported. The flock consisted of approximately 300 Texel sheep, managed in an extensive grazing system. Lambs and adult animals were affected. According to the information provided by the farm owner, many animals presented clinical signs of haemonchosis, and a closantel dose of 20 mg / lamb was administered in all sheep, regardless of body weight. Lambs weighted on average 13 kg. After closantel administration, several sheep presented neurologic signs and died. At the clinical examination, sheep presented pallor of ocular mucous membranes, as well as submandibular edema. Also, 20 lambs showed signs of blindness, disorientation and bumping into objects, as well as hypothermia and lack of response to the menace reflex. Three 30 to 45-day-old male lambs that died spontaneously were submitted for necropsy. Grossly, only mild ascites was noted. Histopathological examination of the retina showed degeneration and fragmentation of photoreceptor layer as well as depletion of the inner nuclear layer, associated with pyknosis and karyorrhexis. There was also a reduction in the number of ganglia cells in the ganglion cell layer and atrophy and vacuolization in the outer plexiform layer. In the optic nerve, multifocal mild to moderate vacuolization was observed. Diffuse perineural and perivascular edema were observed in the brain, predominantly in the grey matter. In the encephalon of one of the lambs, multifocal vacuolization was observed, which was also evidenced at the junction of the white and gray matter of the telencephalon, and in the white matter of the cerebellum. In the trigeminal ganglia, moderate multifocal vacuolization was noted in the perikaryon of neurons. Furthermore, the spinal cord had moderate multifocal vacuolization at the junction of white and gray matter.Discussion: The diagnosis of closantel intoxication in sheep was based on the clinical history and histopathological findings. The association of these data is crucial to suspect and confirm the diagnosis of this type of intoxication. Closantel is an anthelmintic drug widely used in sheep, and in correct doses may be very effective, but when used in doses higher than recommended may lead to irreversible lesions. The optical damage is derived from edema which leads to degeneration of ganglia cells and injury to the optic nerve. Another proposed mechanism is related to optic nerve compression causing rupture and edema of retinal structures. Lesions tend to be dose related, and poisoning usually occurs when treating groups of animals based on the weight of the heaviest animal. Clinical signs of blindness and pupil dilatation are usually seen. There is no effective treatment for reversion of this condition; therefore, prevention based on correct calculation of anthelmintic dose is pivotal. The epidemiological examination, clinical signs and anatomopathological examination were extremely important to make the final diagnosis of this intoxication.

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