Photo : Charlie Riedel ( AP )

Plague-infected fleas affecting prairie dog colonies have forced closures in parts of Colorado, including wildlife areas and a suburb of Denver, as authorities say the fleas could spread the disease to pets and people.


The Rocky Mountain Arsenal National Wildlife Refuge was forced to undergo a temporary closure as a “precautionary measure” last month while it worked to address the issue affecting colonies of black-tailed prairie dogs and endangered black-footed ferrets dependent on them for shelter and food, the U.S. Fish & Wildlife Service said Saturday. While the park has re-opened to visitors with some exceptions, other areas will remain closed as authorities work to address the issue.

According to the Tri-County Health Department, some locations in Commerce City—a suburb of Denver—will remain closed, as will the First Creek at DEN Open Space. Those closures will remain in place through Labor Day Weekend, the health department said.


“The prairie dog colonies are being monitored and burrows are being treated with insecticide, but there is still evidence of fleas in the hiking and camping areas, which could put people and pets at risk, so those areas will remain closed,” John M. Douglas, Jr., executive director of Tri-County Health Department, said in a statement.

According to the Washington Post, the initiative involves treating the burrows with an insecticide powder that, when brushed up against by the prairie dogs can kill the fleas. Additionally, David Lucas of the Rocky Mountain Arsenal National Wildlife Refuge told the Washington Post that aside from insecticide treatments, “there is this secondary effort which is to try to prevent the spread of this disease across the landscape.”

According to the Centers for Disease Control and Prevention, human cases of the plague—which is caused by the bacterium Yersinia pestis—are primarily reported in the western part of the country, including in parts of Arizona, Colorado, California, Nevada, New Mexico, and Oregon. On average, seven cases of people infected with the plague are reported in the U.S. each year, with the most common being bubonic. The two other forms are pneumonic and septicemic.

Symptoms of plague can vary by form but include fever, chills, weakness, abdominal or chest pain, and headache, among others; however, the CDC notes that especially in the septicemic and pneumonic varieties of plague, there are often “no obvious signs that indicate plague.”


Plague can be serious and even deadly in people, but it can be treated with antibiotics. According to the CDC, the sooner an individual seeks treatment, the more likely they are to have a full recovery.

Clarification: This story has been updated to reflect that bubonic is the most common form of the plague in humans in the U.S.; the two other forms are pneumonic and septicemic.