Abamectin poisoning in adult beef cattle and calves in northern and midwestern Brazil

ABSTRACT: Abamectin is an anthelminthic widely used in agriculture, human, and veterinary medicine. The predomination in cases of abamectin toxicosis are neurological changes such as ataxia, lethargy, coma, tremors, convulsions, mydriasis, and blindness. This article describes the clinical, morphological, and toxicological results of cattle accidentally poisoned by abamectin on properties in the states of Rondônia and Mato Grosso, Brazil. Clinical and epidemiological data on the affected herd were collected from the owners, employees, and veterinarians of the properties. A clinical examination was conducted, and a necropsy was performed on the affected animals, with organ samples collected for histological and toxicological analysis. The main clinical signs observed were ataxia, apathy, and death. No significant gross or histologic changes were present. The concentration of abamectin in the brains and livers was > 25.00 μg/kg. The predisposing factors for the occurrence of these outbreaks were visual estimation of cattle weight, standardization of medication doses for batches of cattle, and medication bottle error during application resulting in poisoning and death of cattle. The findings emphasize the need to improve animal management and team training prior to drug application in properties.