$1M Awarded in Equitrol Lawsuit; Farnam Plans Appeal

A jury awarded $1,007,500 to plaintiffs who alleged in a lawsuit that Farnam's Equitrol, a feed-through fly control product, was defectively designed and caused harm to their Thoroughbred and Warmblood sport horses. Farnam countered with a press release stating that it is appealing the decision and believes that the court decision is incorrect on legal and factual grounds.


The jury in the three-week trial in Santa Ana, Calif., over which U.S. District Court Judge James V. Selna presided, ruled in Farnam's favor on another point, which was an allegation that the company intentionally misrepresented the product.

Equitrol's active ingredient tetrachlorvinphos (TCVP) is widely used by several companies in feed-through larvicides for cattle and horses and in fly control products for several other species. Equitrol has been available since 1983 and has been reported as effective in killing fly larvae in the manure before they have a chance to mature. According to Anne Robertson, Public Relations Director for Farnam Companies, both TCVP and Equitrol itself were recently re-registered by the Environmental Protection Agency (EPA). This was because several years ago, the EPA began the process of requiring all older pesticides that were registered with the EPA to go through another in-depth assessment.

Charlotte and Christopher Wrather, owners of Cottonwood Ranch in Los Alamos, Calif., and the ranch's manager/trainer Lori Akari, claimed that they fed Equitrol as directed, and that it caused or exacerbated a variety of health problems in their horses, "including reproductive problems and birth defects, stunted and retarded growth, hyperexcitability and other neurologic dysfunctions, laminitis, immunosuppression evidenced by unusual or unusually severe infections, 'low thyroid,' diarrhea, and colic."

Chris Jacobi, president of Farnam Horse Products, stated in a company release, "We stand by the product's safety and effectiveness reflected by its long-standing tenure in the marketplace. All of our products undergo extensive testing before they can become available to consumers and are designed to help horses and their owners."

Tetrachlorvinphos is an organophosphate cholinesterase inhibitor that generally is considered to have low mammalian toxicity.

Steven Nicholson, DVM, Dipl. ABVT, a veterinary toxicologist at Louisiana State University (LSU) and a livestock extension veterinarian with LSU's Ag Center, said clinical signs in an animal acutely poisoned by organphosphate might include diarrhea, shortness of breath, and sometimes excessive lacrimation (tearing or watering of the eyes). "There also might be some signs of colic in the horse, muscle tremors that might actually proceed into convulsions, and perhaps excessive sweating," he added.

But it is unclear how much organophosphate is toxic to the horse. The Horse spoke with Nicholson and Warren Porter, PhD, of the Department of Zoology at the University of Wisconsin, Madison, an expert witness in the case for the plaintiffs, and looked into past research on TCVP. Researchers are working to learn more about these chemicals and their effects on horses. Visit www.TheHorse.com/ViewArticle.aspx?id=1687 for the full story.

It cannot be definitively proven whether or not Equitrol caused any or all of the problems in the Cottonwood horses because so little is understood about organophosphate toxicity. Farnam holds that more than 30 million doses have been administered since 1983 and that very few adverse events have been reported. The Wrathers believe Equitrol is the only thing that makes the problems with their horses add up.

Porter said the take-home message for horse owners from this trial would be, "You have to live with the consequences of your decisions, and always consult with your veterinarian before using chemicals on your horses."


  • Organophosphates are contained in some feed-through fly control products for horses, cattle, and other species (including tetrachlorvinphos, TCVP, the active ingredient in Equitrol).
  • Organophosphates can cause toxicity in mammals.
  • No one knows how much organophosphate is toxic to horses.
  • Cholinesterase levels decrease in plasma and whole blood after organophosphates are absorbed by horses; plasma levels are more sensitive to the presence of organophosphates. Please see www.TheHorse.com/ViewArticle.aspx?id=1687 for more on this.
  • Unpublished research suggests that TCVP can cause behavior changes in horses.
  • TCVP has been used as a larvicide in horses since 1983 under the name Equitrol.
  • Very few adverse reactions have been reported to the federal government in association with TCVP administration in horses.
  • Check with your veterinarian before using any medications in your horses, especially in those which are debilitated, old, pregnant, or nursing.

About the Author

Stephanie L. Church, Editor-in-Chief

Stephanie L. Church, Editor-in-Chief, received a B.A. in Journalism and Equestrian Studies from Averett College in Danville, Virginia. A Pony Club and 4-H graduate, her background is in eventing, and she is schooling her recently retired Thoroughbred racehorse, Happy, toward a career in that discipline. She also enjoys traveling, photography, cycling, and cooking in her free time.

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