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Plant intoxications in wildlife are difficult to diagnose, are overlooked, or are sometimes even neglected. Hence, factors that induce wild animals to ingest poisonous plants have not been sufficiently documented. An outbreak of glycoprotein storage disease in sambar deer ( Cervus unicolor ), induced by ingestion of the swainsonine-containing plant, common wireweed (Sida carpinifolia), is reported. Nine out of 55 deer held by a zoo in Brazil were affected. The poisoning was characterized by emaciation and neurologic signs followed by unexpected death in some of the animals. Animals presented abnormal consciousness, posterior paresis, and musculoskeletal weakness; less evident were vestibulo-cerebellar signs. Histologically, there was vacuolation of neurons and epithelial cells of the pancreatic acines, thyroid follicules, and renal tubules. Furthermore, in the central nervous system were axonal degeneration, necrosis, and loss of neurons. Three factors may lead to the ingestion of S. carpinifolia by sambar deer: 1) A grazing field with only S. carpinifolia as a source of forage; 2) a large number of animals kept in this field; and 3) a hierarchy within a cervid group in which dominant males isolated and displaced juvenile and weaker adult males, leaving them with access to only S. carpinifolia.

The current study reports the investigation on the cause of sudden deaths associated with cardiac fibrosis in cattle in northern Rio Grande do Sul, Brazil. The exclusion of known causes of bovine cardiac fibrosis as well as the absence of the plants in that region whose consumption has already been linked to the disorder motivated this investigation. The condition, which was attributed to the consumption of Amorimia exotropica, affected draft oxen, most of which died suddenly without showing any clinical signs during usual management or work. Globular hearts with white foci at their cut surfaces were the main gross findings, which corresponded microscopically from multifocal to coalescent areas of myocardial fibrosis. To confirm the condition, A. exotropica from the ranches where cattle died from the disease was dosed to rabbits, which showed similar lesions to those seen in dead cattle after receiving 10 doses of 3.6 g/kg at 4-day intervals. Electron microscopy on rabbit tissues revealed severe tumefaction of the cardiomyocytes associated with mitochondrial swelling, displacement, and rupture of the mitochondrial crests, and of the bundles of myofibrils, apart from large glycogen deposits within the sarcoplasm. It is suggested that mitochondrial changes triggered alterations that lead to cardiac fibrosis and that all of these changes were induced by A. exotropica cardiotoxicity.

Plant poisoning, together with rabies and botulism, are the main causes of death in adult cattle in Brazil. Estimates indicate that about one million head of cattle die annually through plant poisoning in this country. There are approximately 75 plants of practical importance to animal husbandry that have had their toxicity confirmed by experiments with the animal species affected under natural conditions. The great majority of these plants only occur in Brazil and neighbouring countries. A few of them are forage plants that can become toxic under certain conditions. In this review the poisonous plants of interest to animal husbandry of Brazil are divided according to the clinical-pathological picture they cause in cattle; only cyanogenic plants, plants that cause nitrate/nitrite poisoning and the ones that cause oxalate poisoning, are grouped according to their toxic principles. Plants and their toxic principles, or of which possible toxic compounds have been isolated, are listed.