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United States Department of Agriculture

Agricultural Research Service

Research Project: POISONING OF LIVESTOCK BY VARIOUS LARKSPUR SPECIES (DELPHINIUM)

Location: Poisonous Plant Research

Title: Poisoning by Indigofera lespedezioides in horses

Authors
item Lima, Everton -
item Riet-Correa, Franklin -
item Gardner, Dale
item Barros, Severo -
item Medeiros, Rosane -
item Soares, Mauro -
item Riet-Correa, Gabriela -

Submitted to: Toxicon
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 17, 2012
Publication Date: June 1, 2012
Citation: Lima, E.F., Riet-Correa, F., Gardner, D.R., Barros, S.S., Medeiros, R.M., Soares, M.P., Riet-Correa, G. 2012. Poisoning by Indigofera lespedezioides in horses. Toxicon. 60: 324-8.

Interpretive Summary: There are reports the plant Indigofera lespedezioides causes poisonings in horses in northern Brazil. The main signs of poisoning are anorexia, sleepiness, unsteady gait, severe ataxia, weakness, stumbling, and progressive weight loss. A single horse was introduced to a small paddock invaded by the plant and carefully observed of 60 days for signs of poisoning. The first signs were observed 44 days from the start of grazing. The animal was euthanized on day 59 and upon necropsy no significant gross lesions were observed in this animal. A second horse from a clinical case also showed no significant gross lesions. However, upon complete histological examination significant lesions were observed and reported. Chemical analysis of the plant detected a toxic amino acid known as indospicine with concentrations ranging from 63 to 1178 µg/g. Plant samples were also analyzed for nitro toxins but only detected in one of the samples at a concentration of 2.5 mg/g. In conclusion, poisoning by I. lespedezioides is very similar to those poisonings by Indigofera linnaei and Indigofera hendecaphylla. Based on the preponderance of indospince and lack of nitro toxins in the samples it is proposed that indospicine is the toxic compound responsible for the poisoning.

Technical Abstract: Poisoning by Indigofera lespedezioides is reported in horses in the state of Roraima, northern Brazil. The main clinical signs are anorexia, sleepiness, unsteady gait, severe ataxia, weakness, stumbling, and progressive weight loss. To induce the disease experimentally, a 7-year-old horse was introduced in a small paddock invaded by the plant. The first nervous signs were observed 44 days from the start of grazing. The animal was euthanized on day 59. No significant gross lesions were observed upon necropsies of the experimental horse as well as one spontaneously affected horse. Upon histologic examination neuronal lipofuscinosis was observed in the brain, cerebellum, and spinal cord. Wallerian-type degeneration was observed on some mesencephalic tracts. Neuronal and axonal degeneration and lipofuscinosis were observed on electron microscopy examination. Indospicine was detected in four samples of I. lespedezioides with concentrations ranging from 63 to 1178 mg/g whereas nitro toxins could be detected in only one of the samples at a concentration of 2.5 mg/g. In conclusion, poisoning by I. lespedezioides is very similar to those poisonings by Indigofera linnaei and Indigofera hendecaphylla. Based on the preponderance of indospince and lack of nitro toxins in the samples it is proposed that indospicine is the toxic compound responsible for the poisoning.

Last Modified: 8/1/2014
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