Badlands National Park officials in South Dakota have confirmed from testing Friday that the plague killed a large group of prairie dogs, which are rodents the size of rabbits.

The plague hadn’t been detected in the park’s ecosystem since 2009, park officials said in a release Wednesday. The disease came to America via rats brought on ships in the early 20th century.

While South Dakota has never had a case of a human catching the plague, the disease can spread from infected fleas and rodents. Around seven Americans are infected with the plague each year, mainly in the Southwest and California.

The disease is best known for the 14th-century Black Death pandemic, in which the plague killed millions across Eurasia and North Africa.

Cases were reported in South Dakota prairie dogs in 2005, and park officials are concerned about its spread and impact on the black-footed ferret, an endangered species. Around 80% of the remaining ferret population died during the 2009 outbreak, park officials said.

In addition to being susceptible to plague infection, black-footed ferrets rely on prairie dogs as key prey animals.

“We are … taking necessary action to protect this important keystone species. Extensive conservation efforts in 2009 to manage the spread of plague were able to preserve a black-footed ferret population in the Conata-Badlands ecosystem, where the largest free-ranging black-footed ferret population in the world now resides,” Badlands National Park Superintendent Eric Veach said.

• Brad Matthews can be reached at bmatthews@washingtontimes.com.