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Journal of the South African Veterinary Association

On-line version ISSN 2224-9435
Print version ISSN 1019-9128

J. S. Afr. Vet. Assoc. vol.81 n.2 Pretoria Jan. 2010




Polioencephalomalacia associated with closantel overdosage in a goat



E SakhaeeI,*; A DerakhshanfarII

IDepartment of Clinical Sciences, Faculty of Veterinary Medicine, University of Kerman, Iran
IIDepartment of Pathobiology, Faculty of Veterinary Medicine, University of Kerman, Iran




This report describes clinical and pathological findings associated with closantel (a halogenated salicylanilide anthelmintic) overdosage in a 3-year-old goat. The clinical signs included blindness, incoordination, ataxia, depression of the palpebral and pupillary reflexes, and recumbency. No gross lesions were noted in tissue or organs at necropsy, but microscopic lesions were seen in nervous tissue and hepatic cells. Polioencephalomalacia was clearly evident. Bilaterally symmetrical status spongiosus of the white matter of the brain, bilateral laminar necrosis, microcavitations, ischaemic cell change and severe degeneration of the cerebellum were seen in nervous tissue. Fatty change and hydropic degeneration in the liver and hepato-cellular degeneration were observed histologically.

Keywords: closantel, goat, polioencephalomalacia.




The halogenated salicylanilides are a group of compounds developed mainly for their antiparasitic activity in animals. Closantel and rafoxanide, which represent the most important drugs in this group, are used extensively for the control of Haemonchus spp. and Fasciola spp. infestations in sheep and cattle and Oestrus ovis in sheep in many parts of the world7. Clinical signs of closantel toxicity in small stock include inappetence, ataxia, paresis, recumbency, and blindness2. Histologically, widespread spongy changes (status spongiosus) in the central nervous system, optic neuropathy and retinal degeneration have been described. Acute retinal lesions consist of papilloedema, necrosis of the outer retinal layers and retinal separation in tapetal and non-tapetal areas8. However, to the authors' knowledge, there is no report of polioencephalomalacia/cerebrocortical necrosis (CCN) due to closantel poisoning in the veterinary literature.

This publication is the 1st report of polioencephalomalacia associated with closantel overdosage in goat. It describes the progressive development of lesions in the brain and liver in a case of closantel poisoning in a goat.



In October 2007, a 3-year-old goat with a history of closantel (Nasr®, Fariman, Iran) overdosage was referred to the Teaching and Research Hospital of Veterinary Medicine Faculty, Shahid Bahonar University of Kerman, Iran. The clinical findings were characterised by blindness, depression, head pressing, circling, teeth grinding, incoordination, ataxia, depression of the palpebral and pupillary reflexes, nystagmus, and dilated pupils, muscle tremors, frothy salivation and recumbency. In this case, marked opisthotonus, extension of the limbs, hyperaesthesia and periodic tonic-clonic convulsions were observed. The rectal temperature and heart rate were 39.8 ºC and 98 pulses per minute respectively.

Accurate information on the doses administered could not be obtained, but, from inquiries made, it seemed likely that the recommended dose (10 mg/kg, 1m /5 kg live body weight orally) had been exceeded by up to 8 times. This product had been stored below 25 ºC (room temperature) in the closed, original container in a dry, well-ventilated area, and protected from sunlight and its expiry date was at the end of June 2009.

Because of the poor body condition of the animal, the owner selected euthanasia. After necropsy, samples were fixed in 10 % neutral buffered formalin and then submitted to the pathology laboratory. After fixation, tissue samples were embedded in paraffin wax, and sections (5-6 µm) were cut and stained with haematoxylin and eosin (H&E).



Gross lesions

No gross lesions were noted in tissues or organs at necropsy.

Histological lesions

Brain. The lesions were widespread in cerebral cortex, with polioencephalomalacia (CCN) being obvious (Fig. 1). There was bilateral symmetrical status spongiosus of the white matter of the brain, microcavitations and bilateral laminar necrosis (Fig. 2). Ischaemic cell change and severe degeneration of the cerebellum were seen in nervous tissue (Fig. 3).







Liver. Fatty change and hydropic degeneration in the liver and hepatocellular degeneration were observed.

Other organs and tissues. No significant lesions were evident.



The findings in this case of accidental closantel poisoning, and status spongiosus of the cerebral and cerebellar white matter, were similar to those in previous studies3,6,8. However, polioencephalomalacia (CCN), fatty change and hydropic degeneration in liver and hepato-cellular degeneration have not been reported previously. Polioencephalomalacia is a neuropathologic condition of ruminants that can be induced by a variety of neural metabolic disruptions. These include altered thiamine status, water deprivation, sodium ion toxicosis, lead poisoning and high sulphur intake4. The anthelmintic spectrum of closantel has been linked to the compound's ability to uncouple oxidative phosphorylation, but it is not known whether this mechanism could account for the toxic effects in sheep and goats1,7.A primary myelinotoxic effect of salicylanilides on the myelin sheath, especially with vacuolation resulting from overdosage, cannot be excluded5.



This research was financially supported by research council of Shahid Bahonar University of Kerman.



1. Bacon J A, Ulrich R G, Davis J P, Thomas E M, Johnson S S, Condor G A, Sangster N C, Rothwell J T, McCracken R O, Lee B H, Clothier M F, Geary T G, Thampson D P 1998 Comparative in vitro effects of closantel and selected β-ketoamide anthelmintics on a gastrointestinal nematode and vertebrate liver cells. Journal of Veterinary Pharmacology and Therapeutics 21: 190-196        [ Links ]

2. Barlow A M, Sharpe J A E, Kincaid E A 2002 Blindness in lambs due to inadvertent closantel overdose. Veterinary Record 151: 25-26        [ Links ]

3. Borges A S, MendesLCN,De Andrade A L, Machado G F, Peiro J R 1999 Optic neuropathy in sheep associated with overdosage of closantel. Veterinary and Human Toxicology 41: 378-380        [ Links ]

4. Gould D H. 2000 Update on sulfur-related polioencephalomalacia. Veterinary Clinics of North America Food: Animal Practice 16: 481-495        [ Links ]

5. Kreutzberg G W, Blakemore W F, Graeber M B 1997 Cellular pathology of the central nervous system. In Graham D I, Lantos P L (eds), Greenfield's neuropathology (2nd edn). Arnold, London: 85-140        [ Links ]

6. Obwolo M J, Odiawo G O, Ogaa, J S 1989 Toxicity of a closantel-albendazole mixture in a flock of sheep and goats. Australian Veterinary Journal 66: 229-230        [ Links ]

7. Swan G E 1999 The pharmacology of halogenated salicylanilides and their anthelmintic use in animals. Journal of the South African Veterinary Association 70: 61-70        [ Links ]

8. Van der Lugt J J, Venter L 2007 Myelin vacuolation, optic neuropathy and retinal degeneration after closantel overdosage in sheep and in a goat. Veterinary Pathology 33: 495-502        [ Links ]



Received: November 2008.
Accepted: March 2010.



* Author for correspondence. E-mail:

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