Kansas City, Mo ? Casey, an African elephant that had been a popular attraction at the Kansas City Zoo since the mid-1950s, has died after a long stretch of declining health.

The elephant, born in the wilds of central Africa, arrived at the zoo in 1955. An estimated 52 years old, he was the oldest bull African elephant in North America and believed to have been the oldest in captivity anywhere.

Zookeepers found him lying on his side early Wednesday morning in his outdoor enclosure. His death is presumed to have been caused by old age.

For the past decade or so, the zoo staff had bathed and treated Casey’s feet twice a day because he suffered from chronic arthritis and localized infections. Recently he sometimes had begun to refuse to cooperate with the treatment.

Casey also had cataracts and was believed to be on the last of six sets of teeth, but still was able to eat hay.

“He looked old and worn,” said Kirk Suedmeyer, the zoo’s chief veterinarian. “That is part of a slow progression. Like an old person, he lost muscle tone and lost muscle mass.”

Suedmeyer had last looked in on Casey about 6:30 p.m. Tuesday. The animal is believed to have died peacefully during the night.

The elephant was known as Casey A. when he arrived in Kansas City, along with a female named Lady A. They were named in honor of the Athletics, the major league baseball team that had moved to Kansas City from Philadelphia, later pulling up stakes again for Oakland.

The two were imported for $8,000, about $1,000 of which was raised in a public drive. The rest was paid by A’s owner Arnold Johnson and by Phillip Small, president of Parkview Drugs Inc.

Small started a fund drive after reading an editorial in The Kansas City Star, and said, “If we have a major league baseball team, we should have a major league zoo.”

Lady A. died in 1971. The zoo has another bull elephant, named Dale, and six females.

Casey, considered the largest elephant in North America as well as the oldest, was estimated to have weighed six to seven tons.

For all his size, Casey was usually tolerant of keepers, although he injured two of them in separate incidents in 1982. In the first case, he grabbed a keeper with his trunk and pulled him into a pool, later tossing and kicking him around.

Ten weeks later Casey slammed another keeper into a steel door, breaking his spine and leaving him paralyzed. A year later the keeper took his own life.