Scientists Find New Clue to Treat Lethal Horse Disease

By Jill Lee
February 5, 1999

A disease that destroys brain cells in horses, equine leukoencephalomalacia (ELEM), is currently a death sentence. But promising new research findings may someday improve the odds.

ELEM is caused by corn contaminated with the fumonisin-producing fungus, Fusarium moniliforme. The toxin is insidious--only a small amount makes horses sick. While the animals appear healthy, they suffer irreversible damage.

Scientists at USDA’s Agricultural Research Service and Animal and Plant Health Inspection Service, in collaboration with Emory University, found that the fungi’s toxin interrupts the way a horse’s liver, kidney and lungs make a special kind of fat known as sphingolipid. The toxin also causes an inappropriate fat intermediate (sphinganine) to accumulate and other necessary fats to be depleted.

The ARS researchers are based at the agency’s Richard B. Russell Agricultural Research Center in Athens, Ga. They found that another fungus, Isaria sinclairii, produces a compound called ISP-I or myriocin that temporarily reduced the sphinganine accumulation in mice with no ill effects. If confirmed by other studies, the myriocin discovery might lead to treatments.

Animals exhibiting neurological effects of fumonisin poisoning can’t be saved. But for other members of the herd exposed to contaminated food, the downward spiral of sphinganine overproduction could be stopped. The results of the preliminary studies in mice are being published in Environmental Toxicology and Pharmacology.

ARS and Emory scientists have received a patent on a technique to detect fumonisin poisoning in an animal’s tissue, serum and urine. It’s based on changes in sphinganine.

Fumonisin poisoning is not common in the United States, but it does happen. In 1995, 38 horses in Kentucky and Virginia died from it. The Food and Drug Administration is considering setting guidance amounts to protect both humans and livestock, following long-term exposure studies.

ARS is the chief research agency of the U.S. Department of Agriculture.

Scientific contact: Ronald Riley, Toxicology and Mycotoxin Research Unit, ARS Richard B. Agricultural Russell Research Center, Athens, Ga. Phone (706) 546-3377, rriley@ars.usda.gov.