"We tried numerous antibiotics, and different treatments, and different strengths of medications, and we just were not able to clear it up," said Dr. Nancy Carpenter, Associate Director of Animal Heath at Hogle Zoo.
To help little Eli, Dr. Carpenter had one last idea.
"We took him to the University for a CT scan, and that's when we realized we needed an ear, nose, throat specialist," explained Dr. Carpenter.
That's where Dr. Richard Orlandi, with University of Utah Health Care came in.
“The infections been there a long time, it had really thickened up, and so he'd have probably been uncomfortable for a long time," said Dr. Orlandi.
Dr. Orlandi did an endoscopic procedure on Eli Tuesday morning to treat his infection.
"This is my first monkey surgery," said Dr. Orlandi.
"Because we look at so many different animals with so many different problems, we do rely on specialists to help us out," explained Dr. Carpenter.
All of the medical tools used on Eli were what Dr. Orlandi would use on a human, but because of Eli's tiny size, he used pediatric-sized equipment.
“The staff prepared me well about the differences. He has some flaps that come down his nostrils that I kept working around," said Dr. Orlandi.
For Eli, the future looks bright.
"We're really thrilled with what we've been able to accomplish. Got both sides of the sinuses taken care of,” said Orlandi.
Hogle Zoo's staff hopes Eli can now go back to being the howler monkey he always was -- happy and healthy.