A Wayson stain of Yersinia pestis, the bacteria that causes bubonic plague, in an undated image. A Denver Zoo monkey has died of bubonic plague, apparently after eating a squirrel stricken with the disease, Colorado health and zoo officials said on Monday. REUTERS/CDC/Handout

DENVER (Reuters) - A Denver Zoo monkey has died of bubonic plague, apparently after eating a squirrel stricken with the disease, Colorado health and zoo officials said on Monday.

Five squirrels and a rabbit found dead on zoo grounds tested positive for the flea-borne disease in recent weeks, Denver Zoo spokeswoman Ana Bowie said.

Zookeepers on May 15 noticed the 8-year-old hooded capuchin monkey was lethargic, and the next day it was found dead in its enclosure. Zoo veterinarians sent tissue samples to a state laboratory where it was determined the animal died of the plague. The death was announced on Monday.

Zoo veterinarian Dave Kenny said that the risk of plague spreading to humans was extremely low but that visitors were being urged to avoid squirrels and rabbits.

“There are species in the zoo collection, especially monkeys, that could be susceptible to the plague,” said John Pape, an epidemiologist with the Colorado Department of Public Health and Environment.

Bowie said none of the 17 other capuchin monkeys in the exhibit -- or any other animals at the zoo -- have shown plague symptoms. But as a precaution, all the capuchin monkeys have been moved to an inside enclosure and are being treated with a regimen of antibiotics, she said.