Mare Reproductive Loss Syndrome

By George Grow

This is the VOA Special English SCIENCE REPORT.

Scientists and animal experts have been searching for a killer in the American state of Kentucky. Hundreds of horses on Kentucky farms have suffered failed pregnancies in the past few weeks. Many horses one year of age or younger also have died unexpectedly.

The mysterious killer has had a major effect on the state's economy. Reports estimate the Kentucky horse industry has lost hundreds of millions of dollars.

Kentucky farms produce some of the world's finest pure breed horses. They normally produce about ten-thousand thoroughbred foals each year. That represents about one-third of the country's racehorses.

The University of Kentucky has received reports of more than five-hundred dead foals or failed pregnancies since late April. Animal experts are calling the problem Mare Reproductive Loss Syndrome.

There have been unexplained horse deaths in Kentucky before. Many horses had failed pregnancies during the spring of Nineteen-Eighty and Nineteen-Eighty-One. In those years and this year, Kentucky had lower than normal temperatures in March. This was followed by higher than normal temperatures in April.

Scientists thought the deaths this year might have resulted from an unknown disease or fungus. Fungus infections can produce harmful substances, called mycotoxins. However, most tests showed mycotoxins were not responsible for the problem. The investigation also found no evidence of an infectious disease.

Recently, the scientists began studying a possible link to Eastern Tent Caterpillars. There have been large numbers of the insects in Kentucky during the past two years. Tent caterpillars feed on cherry tree leaves. Some of the affected horses lived in fields near cherry trees.

Two weeks ago, the investigators announced progress in their search for the cause of Mare Reproductive Loss Syndrome. They said cyanide poison was to blame for the deaths this year. The scientists said wild black cherry trees probably produced the cyanide. They said pregnant horses may have gotten the cyanide by eating the leaves from the cherry trees or the caterpillars.

The scientists say their observations still must be confirmed. And they say their findings have not yet met what they call reasonable standards of scientific proof.

This VOA Special English SCIENCE REPORT was written by George Grow.