The Oregon Zoo has seen its share of death over the last year.

In July, one of the zoo's most popular animals, Conrad the polar bear, was euthanized after veterinarians found a tumor on his liver. Less than six months later, Conrad's sister, Tasul, was also put down after officials at the zoo discovered the elderly bear had developed an aggressive form of ovarian cancer. They were both 31, considered geriatric in bear years.

Then, on Thursday, the zoo euthanized its most famous inhabitant, local icon Packy the elephant, after a long battle with a form of tuberculosis that had become resistant to treatment. His death came despite the fact that his keepers said, as recently as mid-January, that the 54-year-old pachyderm, one of the oldest in captivity, wasn't showing any symptoms of the affliction.

Zoo officials decided to put him down because they wanted to act before the old bull began suffering in earnest. They also wanted to avoid a potentially catastrophic scenario in which Packy's drug-resistant strain of the disease spread to the rest of the herd.

Not everyone at the zoo was convinced that Packy's time had come, acknowledged deputy director Sheri Horiszny.

"Everyone was agreed on the outcome," she said. "But there were some disagreements on the timing."

Some of the most strident, and public, disagreement came from a Facebook page called "Team Packy." Since early December, when officials discontinued treatment for Packy's TB, posts on the page, which is run by a current elephant keeper and a former zoo employee, have raised questions about Packy's condition and the zoo's decision to end his life.

According to the Facebook page, the zoo had a multitude of concerns about the iconic 54-year-old bull elephant, ranging from his quality of life to transmission of the disease to many of the unknowns surrounding tuberculosis in elephants.

The thread through all of the discussions on the page, however, has been about preventing a rushed outcome, especially since Packy was showing no outward signs of the disease.

In January, Bob Lee, who has worked with Packy since 1999, said the elderly pachyderm was "doing well" and that he "might be the only one who doesn't know he has tuberculosis."

But by the third week in January, zoo officials were pushing for a move on Packy, according to the Facebook page.

"We have been told that they 'have to make the decision soon' about Packy," the authors of the page wrote. "Why the rush? His health is good, great even, he's active and engaged, he's in a safe place, they have assured us the herd and the staff are safe.

"We all accept that Packy will eventually need to be euthanized because of this disease or other health issues, but the decision boils down to whether he is euthanized now because of the fear of transmission or whether he is euthanized later because we have determined a decline in quality of life and don't want him to suffer. Why is the decision urgent?"

Horiszny said the decision on the timing of the euthanasia was made over months as she met with hundreds of people -- including Packy's keepers, volunteers and administrators -- to explain the situation he faced and what the options were.

"We all love Packy," she said. "Everyone had a slightly different opinion on how to address a very difficult situation."

They considered continuing what they were doing -- leaving Packy as he was without treatment -- but Horiszny said that was considered too cruel. They thought about sending him somewhere else, but elephants don't do well with abrupt change late in life and the zoo also had to consider the risk to other elephants. They also considered treating him with different drugs, but it would have been a cocktail of four to seven substances, none of which had been tested in elephants and all of which had harsh side effects in humans.

Ultimately, the fourth option, euthanasia, was settled upon. On paper, that decision was made by Don Moore, the director of the zoo, but Horiszny said Moore had input from numerous stakeholders and experts.

In Packy's case there were no outward signs of decline, but lab results indicated the disease was progressing. The deciding factor in when to euthanize was ensuring Packy did not suffer, Horizsny said.

"There was nothing special about the timing other than making sure Packy's last day was not his worst day."

That criteria was the product of months of deliberations, said Lisa Moses, a veterinarian and bioethicist at the MSPCA-Angell Animal Medical Center in Boston. She specializes in end-of-life care for animals and the zoo reached out to her last year to consult on Packy.

"When you decide euthanasia is the best course of action, the big decision is: Do you want to wait until there is a crisis or make that decision to prevent further suffering," Moses said. "There was a real fear that there was a crisis looming."

Packy's situation was complicated because, as keepers said repeatedly, the old bull wasn't showing any outward symptoms of his affliction, which include weakness, weight loss and coughing.

But that could have been a result of his discontinued treatment in December, Moses said, as the drugs he was on -- and eventually grew resistant to -- had some harsh side effects that would have gone away when treatment ended.

Beyond the concerns over how Packy was feeling, zoo officials were also worried about exposing others to Packy's strain of tuberculosis. He had been quarantined since at least late 2015, according to Horiszny.

"There was a real concern that his life was being negatively impacted by isolation," Moses said.

Horiszny commiserated with members of the staff who are heartbroken over Packy's death, but she stood by the zoo's decision.

"This was a challenge," she said. "We have an incredibly dedicated staff who come to work every day and make decisions meant to give our animals the best life they can have. One day, the best decision is for it to end."

Despite that, the folks who run the Team Packy page were disillusioned with the short notice they received.

"Keeper staff were the last ones to know of the final decision to put him down and were given very little time to say goodbye to a friend that some of us have worked with for decades," they wrote. "When we were told, our only thoughts were to spend what little time was left with him and to ensure that his passing was done with the dignity, love, and respect he was due."

Horiszny said that, on Packy's last day, his keepers were notified that the end was impending and they spent the afternoon with the old bull, brought him a cake and said their goodbyes.

Alan Sironen, who worked at the Cleveland Metroparks Zoo for 35 years before leaving to run Zoo Consultants International, said that it is common for there to be some second-guessing after the death of a high-profile and much beloved animal like Packy.

"Our relationships with animals are just as important as our relationships with other humans and there are going to be levels of grieving and mourning," he said. "When you have to make these decisions, there are always going to be some questions."

Horiszny said that the zoo was working to set up a public celebration of Packy's life and would announce it as soon as the date was finalized.

--Kale Williams

kwilliams@oregonian.com

503-294-4048