Poisoning by Marsdenia hilariana and Marsdenia megalantha (Apocynaceae) in ruminants

Plants causing poisoning outbreaks of livestock in South America: A review

This paper reviews toxic plants for livestock in South America. We included 219 plants in this review, considering only the plants that caused at least one demonstrated outbreak of poisoning. Plants reported as toxic in other regions and present in South America, but with no confirmed outbreaks of poisoning in this region, are not included. We report the main aspects of the epidemiology, clinical signs, pathology and economical importance of the poisonings. Initially, the toxic plants are described based on their toxic compounds, but because the toxic compound is unknown in 92 (42%) of the plants we also classify them according to the affected system. This review highlights the great diversity of toxic plants capable of affecting livestock in South America, and for this reason studies in this regard should be intensified.

Toxic plants affecting the nervous system of ruminants and horses in Brazil

ABSTRACT: This review updates information about neurotoxic plants affecting ruminants and equidae in Brazil. Currently in the country, there are at least 131 toxic plants belonging to 79 genera. Thirty one of these poisonous plants affect the nervous system. Swainsonine-containing plants (Ipomoea spp., Turbina cordata and Sida carpinifolia) cause numerous outbreaks of poisoning, mainly in goats, but cattle and horses are occasionally affected. The poisoning by Ipomoea asarifolia, a tremorgenic plant, is very common in sheep, goats and cattle in the Northeastern region and in the Marajo island. Poisoning by the pods of Prosopis juliflora are frequent in cattle in Northeastern Brazil; occasionally this poisoning affects goats and more rarely sheep. Some poisonings by plants, such as Hybanthus calceolaria, Ipomoea marcellia and Talisia esculenta in ruminants and Indigofera lespedezioides in horses were recently described and needs to be accurately investigated about its occurrence and importance. Other plants poisonings causing nervous signs in ruminants and equidae are less important, but should be considered for the differential diagnosis of neurologic diseases.

Evaluation of Acute and Subacute Oral Toxicity Induced by Ethanolic Extract of Marsdenia tenacissima Leaves in Experimental Rats

The objective of this study is to evaluate the acute and subacute toxicity of the ethanolic extract of Marsdenia tenacissima (MTE) leaves (family: Asclepiadaceae) in albino rats. The acute toxicity was performed where the limit dose of 5000 mg/kg body weight used. Observations were made and recorded for 24 h, and once daily further for a period of 14 days. The rats were weighed and various observations, like mortality, behavior, injury, or any signs of illness were conducted once daily during the period. For subacute study, four groups of 10 animals (female rats) received 10% Tween 20 in distilled water (control), and 250, 500, and 1000 mg/kg of freshly-prepared extracts, respectively, every 24 h orally for 28 days. At the end of each study, hematological analysis and biochemical parameters were evaluated. Histopathological examination of vital organs of the animals were taken for gross findings, compared to controls. There was no significant difference (p > 0.05) observed in the relative organs, body weights, hematological, biochemical parameters, and gross abnormalities, compared to the control. No mortality was recorded. Therefore, analysis of results may lead to the conclusion that the medium-term oral administration of the MTE leaves for 28 days does not cause toxicity.

Spontaneous and experimental poisoning by Marsdenia megalantha Goyder & Morillo in ruminants and a pig

Marsdenia megalantha is a rupicolous shrub with succulent roots from the semiarid region of Brazil that is known to cause fatal poisoning in livestock. We reported spontaneous cases of poisoning by M. megalantha roots in bovine, caprine, ovine, and equine species. The clinical and pathological findings of experimental administration of M. megalantha to sheep, goats, a calf and a pig are reported. Three goats, two sheep and a calf were dosed once orally with freshly chopped roots at dose of 25 g wet plant/kg bw; another sheep and a pig were dosed with 10 g wet plant/kg bw. Poisoning occurred in all of the animals except the three goats. Clinical signs of poisoning included tachycardia, opisthotonus, ruminal bloat, dyspnea, nystagmus, mydriasis, ataxia, and recumbence with paddling movements. Pathological evaluation showed segmental laminar neuronal necrosis and spongiosis in the telencephalic cortex and degeneration of Purkinje cells. The picrate paper procedure detected no cyanide in the plant roots, but the reaction used for nitrate detection gave a strongly positive response. In conclusion, M. megalantha is a poisonous plant that produces acute poisoning characterized mainly by nervous disturbances. Livestock producers should offer alternative food during the dry and early rainy seasons to avoid the poisoning by this plant.