One of only four northern white rhinos believed left in the world has died at the San Diego zoo safari park.

Nola, a 41-year-old female who has been at the park since 1989, was put down on Sunday after her health worsened, a statement from the zoo said.

She had arthritis and other ailments and was being treated for a bacterial infection linked to an abscess in her hip.

Nola had surgery on 13 November to drain the abscess but her health began to deteriorate about a week ago; her appetite faltered and she became listless. Her condition got worse over the past 24 hours and vets decided they had to put her down, according to the zoo.

“Nola was an iconic animal, not only at the San Diego zoo safari park, but worldwide,” the statement said.

The remaining three northern white rhinos, all elderly, are in a closely guarded preserve in Kenya.

The subspecies has been pushed to the point of extinction by poachers, who kill the rhinos for their horns. They are in high demand in parts of Asia where some believe they have medicinal properties for treating everything from hangovers to cancer.

In an effort to preserve the species, the San Diego zoo took possession this month of six female southern white rhinos from South Africa.

Zoo researchers are working on developing northern white rhino embryos to be implanted in the six new arrivals, who will serve as surrogate mothers.