Clinical communication — Kliniese mededeling Polioencephalomalacia associated with closantel overdosage in a goat

INTRODUCTION 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 world. Clinical signs of closantel toxicity in small stock include inappetence, ataxia, paresis, recumbency, and blindness. 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 areas. 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. CASE HISTORY 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 °C 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, 1 m /5 kg live body weight orally) had been exceeded by up to 8 times. This product had been stored below 25 °C (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).