Intoxication by Senecio spp. (Asteraceae) in horses in Uruguay

Abstract

Two outbreaks of Senecio spp. intoxication in horses, occurred in Paysandú County between November 2009 and January 2010 are described. In both situations animals grazed during last winter, paddocks with low forage availability and plenty of Senecio spp. plants. Mainly young animals were affected. Clinical signs were: loss of weight, excitability or depression, aimless walking, circling, head pressing, ataxia, tenesmus and death. In the first outbreak morbidity was 24% and mortality 20.6%, whereas in the second morbidity was 20% and mortality 15.5%. At necropsy liver was firmer, with darker parenchyma or enhancement of the lobular pattern. It was also found mesenteric edema, moderate ascites and in some animals hydropericardium. Main histopatological findings were in liver hepatomegalocytosis, biliary hyperplasia, fibrosis and presence of regeneration nodules; in central nervous system there were spongy degeneration of cerebral white matter, Alzheimer type II astrocytes, and mild perivascular and perineuronal edema.