Testing from a northwest South Dakota prairie dog confirms plague as the cause of a late May prairie dog die off, according to the National Park Service and the U.S. Forest Service. At stake is the largest free-ranging black-footed ferret population in the world.

“We are concerned about the impacts to the black-footed ferret population and are taking necessary action to protect this important keystone species,” said Eric Veach, superintendent of Badlands National Park.

The disease has been detected in Badlands National Park, Buffalo Gap National Grassland, and the greater Conata-Badlands ecosystem, where the largest free-ranging black-footed ferret population in the world now resides. The disease has not been detected in Conata Basin since 2009, when it was responsible for killing more than 80% of the remaining population black-footed ferrets, one of the most endangered mammals in the world.

While the risk to humans remains low, plague is concerning. Plague is a non-native bacterial disease that occurs in rodents and their fleas throughout the western United States. It was introduced into the U.S. from rats aboard ships in the early 1900s and has since become endemic through the Western U.S.

A spokesperson for the Wyoming Game and Fish Department said the event is “certainly on our radar.”

“Right now we are not seeing any plague events in Wyoming, and do not expect the South Dakota event to have an impact to us,” said Public Information Officer Breanna Ball.

While the Game and Fish Department is not working in any capacity with South Dakota with the outbreak, they are watching to see how the outbreak progresses.

“We will likely see more plague in the state, but it is because it can exist in the environment at low levels until we see an outbreak,” Ball said.

Approximately seven human cases occur every year, primarily in the southwestern U.S. and California. Most cases are transmitted through the bite of an infected flea, but humans can also be infected through contact with infected rodents, including animal carcasses, or by breathing infectious particles from an infected animal, sick pet or sick human. South Dakota has never reported a human plague case, although cases in rodents such as prairie dogs were first reported in 2005, according to the National Park Service.

Plague is a rare disease but is a risk throughout much of the West. Symptoms usually begin two to six days after exposure and include flu-like symptoms such as fever, chills, and muscle aches, as well as painful swelling at the site of a flea bite and the nearest lymph node. Symptoms can progress to blood infection and severe respiratory illness if not treated promptly. Plague can be treated with antibiotics but can be fatal if treatment is delayed. Although rare, people infected by breathing in infectious bacteria develop symptoms within one to three days and the infection is most often fatal if not treated shortly after the onset of symptoms. 

The Forest Service advises people avoid contact with rodents and their fleas and burrows, wear insect repellent when working or recreating outdoors, wear long pants tucked into socks and closed-toe shoes, never touch or approach a sick or dead animal, and never feed wildlife, do not pitch tents near rodent burrows, keep pets leashed and current on a flea and tick preventative and know the signs and symptoms of plague. If you develop fever, chills, swelling at the site of an insect bite or nearby lymph node, seek medical care immediately and inform your doctor you may have been exposed to plague.

The National Park Service, U.S. Forest Service and conservation partners are working to apply emergency flea control agents to stop the further spread of plague and to monitor for plague activity in the Conata-Badlands ecosystem to protect the black-footed ferret population and reduce any risks to human health. Additionally, black-footed ferrets are being captured and vaccinated against plague.