Hepatic Encephalopathy Secondary to Chronic Liver Lesions Caused by Crotalaria incana in a Bovine

Abstract

Background: Crotalaria spp. Poisoning induces liver or pulmonary disease. C. mucronata, C. juncea, C. spectabilis, and C. retusa are the Crotalaria spp. inducing spontaneous intoxication in livestock in Brazil. C. mucronata and C. juncea are associated with interstitial pneumonia, while C. retusa and C. specatabilis induce hepatotoxicosis. The toxic principle in Crotalaria spp. are dehydropyrrolizidine alkaloids and their N-oxides. C. incana poisoning to livestock is rarely documented. This paper reports the clinical signs and pathological findings of a case of Crotalaria incana poisoning in a steer. The chemical finding of a potential toxic dehydropyrrolizidine alkaloid in the plant is documented for the first time.Case: The affected bovine was part of a herd of 80 two-year-old steers that were transferred from Property 1 to Property 2, 30 days prior to the event. In the pasture of Property I - where the steers were held for 6 months - there was a heavy infestation by a Crotalaria species with signs of being consumed by the steers. The plant was identified as Crotalaria incana at the Botanical Laboratory of the Federal University of Mato Grosso do Sul and a voucher specimen was filed there under the register GCMS 51169. Two days after entering Property 2 one of the steers became depressed, staggering, and in poor body condition. With time, the steer became oblivious to the environment and died 20 days after the onset of the clinical signs. Significant necropsy findings were limited to the liver which was markedly enlarged and with rounded edges. The hepatic cut surface was mottled with dark red and extensive orange areas of discoloration. The gallbladder was distended and the bile was inspissated. Microscopically, in the liver, there was fibrosis, bile duct hyperplasia and hepatocellular megalocytosis. The Glisson’s capsule was markedly thickened by fibrosis. In the brain, there was vacuolation of myelin sheaths (status spongiosus), moderate gliosis, and rare Alzheimer type 2 astrocytes.Discussion: The diagnosis of intoxication by C. incana was based on clinical signs and pathological changes and the evidence of the plant being consumed. The high infestation of C. incana in the pasture, the high proportion of dead matter and the low concentration of viable pasture favored the ingestion of C. incana. Spongy degeneration, a typical lesion of hepatic encephalopathy, was observed in the several areas of the brain. Cirrhosis of the liver as seen in the case of this report, results in elevated ammonia levels in the blood - and eventually in the brain – and ammonia toxicity causes hepatic encephalopathy. Morphological changes in hepatic encephalopathy in the central nervous system of human beings and horses centers on astrocytes which undergo Alzheimer type 2 change developing an enlarged, pale nuclei with a rim of chromatin and prominent nucleoli. Astrocytes pairs and triplets are seen, and, in severe cases, astrocytic nuclei may become lobulated and contain glycogen. Chemical analysis of C. incana was accomplished by acid-base extraction with zincreduction of N-oxides and quantitation by spectrometry. Quantitative analysis was achieved by liquid chromatography-mass spectrometry. To confirm the identity of the alkaloid in the sample of C. incana the isolated alkaloid was compared to a standard sample of usaramine previously isolated, and its identity verified by magnetic resonance spectroscopy analysis. The 1,2-dehydropyrrolizidine alkaloid usaramine, as well as its  N-oxide, were identified as the major alkaloids in in C. incana. The concentration found in the seed was consistent with that previously reported. This is a new finding on the toxic principle of C. incana. Keywords: cattle diseases, poisonous plants, pathology, hepatotoxicity, Crotalaria incana, chronic liver failure.