Palicourea marcgravii (Rubiaceae) poisoning in cattle grazing in Brazil

Palicourea marcgravii is the most important poisonous plant of cattle in Brazil. It contains monofluoroacetic acid and causes sudden death associated with exercise. Herein, we describe the temporal and spatial distribution of the toxic disease. The survey was based on the epidemiological, clinical, and pathological data of the Setor de Anatomia Patológica (SAP) of the Universidade Federal Rural do Rio de Janeiro (UFRuralRJ) to report outbreaks of poisoning by P. marcgravii, from 1953 to 2018. Clinical signs were peracute and included labored breathing, loss of balance, muscle tremors, lateral recumbency, and limb paddling. Gross lesions such as congestion of large vessels and edema and pulmonary congestion were observed. Multifocal areas of vacuolar hydropic degeneration of distal contorted tubule cells with nuclear pyknosis were observed in the kidneys. The plant is found in forests, and the poisoning occurs mainly after clearing forests for pasture, in areas of natural forest recovery called "capoeira," which provide a favorable environment for maintaining P. marcgravii growth. Outbreaks of P. marcgravii poisoning coincided with periods of creation of large deforested pastures in the Southeast and Midwest regions of Brazil, and the poisoning should be considered an additional risk after deforestation. The most effective prophylaxis is fencing off the forest areas that contain these plants.