Cocklebur Poisoning

Did you know that cockleburs (Xanthium genus), those annoying burs that stick to your clothes and scratch your skin, are toxic if consumed?  Most people are not in the habit of consuming the prickly, spiny seed pods, but they can be incorporated into animal feeds and hay.  Horses, pigs, and cattle can all become poisoned.  Pigs are the species most commonly poisoned from these seedlings.  
  
Cocklebur seeds and seedlings contain a potent toxin called carboxyatractyloside.  The plant actually produces this toxin to eliminate its competition.  Not only is carboxyatractyloside poisonous to animals, it is also a potent plant-growth inhibitor against other plants competing for pasture space.  

Clinical signs of poisoning are primarily neurologic (affecting the brain and central nervous system) and are actually secondary to liver failure.  Affected animals are weak, ataxic (unbalanced), and depressed.  Convulsions are common.  Poisoned animals may vomit and have muscle spasms.  Vasculitis may cause swelling and edema of the feet and legs which is known as “stocking up.”  Mortality rates are high in animals having consumed large amounts of the toxin.  Lower levels of toxicity will often cause chronic liver failure, and therefore a failure of the animal to thrive.

Diagnosis is typically made by identifying exposure in feedstuff and documenting blood chemistry changes related to liver failure.

Treatment is primarily supportive and symptomatic.  When identified early, mineral oil and activated charcoal given by mouth may be beneficial in limiting absorption.  Stimulants such as physostigmine may help in depressed individuals.  Anticonvulsants may be necessary to control seizures.  

References:

Kahn, Cynthia, Ed.  The Merck Veterinary Manual.  9th Ed. P. 291, 2444-2445.

Smith, Bradford.  Large Animal Internal Medicine.  Mosby. St. Louis. 2nd Ed.  1996.  Pp. 1884.

Stegelmeier, Bryan. “Knowledge is Key to Safety, Plants that Poison Horses.”  DVM.  August 2007. 8E-13E.