Horse Deaths Blamed On El Niño

El Niño, the all-purpose excuse for everything from droughts to major hurricanes, is now being blamed for outbreaks of a deadly epidemic among horses.

English scientists have found evidence tying El Niño, the abnormal warming of the Pacific Ocean that causes weather extremes, to African Horse Sickness (AHS). The findings are reported in Thursday's issue of the journal Nature.

After reviewing horse breeding records dating to 1803, researchers found that 13 of the 14 major outbreaks of AHS among South Africa's equine population occurred during extreme conditions known as the warm-phase El Niño.

The 14th outbreak, in 1996, wasn't during an El Niño year but unfolded during similar weather -- a drought followed by heavy rains.

"It creates ripe conditions for the disease to spread. What's important here is that it almost always occurs only when El Niño is present," said Matthew Baylis, a researcher at the Institute for Animal Health in Surrey, England.

Baylis and his colleagues believe the outbreak begins because the drought dries up water sources, driving disease-carrying zebras into contact with horses in their search for water. Small, biting insects called midges then spread the disease from zebras to horses.

When heavy rains end the drought, the population of midges soars, accelerating the spread of AHS. The disease kills 95 percent of horses that become infected.