The area infected with the plague in Conata Basin has more than doubled in the past two weeks, threatening to overwhelm efforts of insecticide-dusting crews trying to keep the disease from decimating endangered black-footed ferrets there.
Federal officials connected with the effort to preserve the rare ferrets in Conata Basin and Badlands National Park say they face an uphill battle.
Sylvatic plague was confirmed last month in dead prairie dogs found in Conata Basin, home to about 300 of the rare black-footed ferrets. The plague already has killed large numbers of prairie dogs and probably has killed some ferrets in the area, wildlife experts say.
Officials with Badlands National Park and the U.S. Forest Service, which administers Conata Basin, are cautioning visitors to the area against handling dead prairie dogs and advising them to keep their pets in their vehicles, although they say the plague doesn't pose a major risk to humans.
But the plague could kill many of the ferrets that were reintroduced to Conata Basin in the mid-1990s and compromise the site as a haven for the animals that were once believed to be extinct. Until this year, Conata Basin was seen by wildlife advocates as the most successful ferret reintroduction site in the country.
And the plague hasn't yet reached the major ferret populations in the region yet, according to Kevin Atchley, Wall district ranger for the Forest Service, which manages Buffalo Gap National Grassland, including Conata Basin.
"The plague is getting a lot closer to some of those, and we haven't been able to get out and dust them," he said.
It hasn't reached Badlands National Park yet.
But the plague area has increased from 4,000 acres two weeks ago to about 9,000 acres now, Atchley said.
"Considering the plague area has doubled in the past couple of weeks, we're probably not going to stay ahead of it," said Scott Larson, a biologist with the U.S. Fish & Wildlife Service in Pierre. "It might very well overwhelm us," Larson said.
Rains over the past few weeks have slowed efforts of crews to dust prairie dog burrows with an insecticide that kills fleas. The plague kills most prairie dogs, which are the main source of food for the endangered ferrets. It is also deadly to the ferrets, which can get it from fleas or by eating plague-infected prairie dogs. The ferrets can also catch it from each other through coughing and sneezing.
So far, crews have dusted about 720 acres of a prairie dog town occupied by ferrets in the park along Sage Creek Road and about 530 acres of a dog town occupied by ferrets in Conata Basin. But that's only about 12 percent of the 10,000-acre goal, Atchley said.
Most of those acres contain prairie dog towns known to host ferrets, but some dusting will be done along S.D. Highway 44 and Conata Basin Road to protect humans, Atchley said.
The insecticide is spread on the prairie dog burrows so when the animals enter or leave, it gets rubbed into their fur and kills the fleas.
Crews will also experiment with other products to battle the fleas, he said.
Crews have begun trapping ferrets and vaccinating them against the plague, Larson said. As of a couple days ago, 19 ferrets had been vaccinated in an effort that will continue for several weeks, he said. However, he said, the animals need two vaccinations several weeks apart for maximum effectiveness.
Larson and Atchley are clearly worried about the fate of the rare ferrets as the plague advances toward them.
"It's like a slow biological fire," Atchley said. "It's not like a wildfire that really rips through an area. But it is moving, and we have to figure out how to head it off."
The disease could compromise the basin as a ferret introduction site, Larson said. "It could take out most of the areas."
A few years ago, the plague wiped out reintroduced ferrets in three sites in Montana.
There are 600 to 800 black-footed ferrets at about 15 other reintroduction sites, Larson said. But most of those already have the plague, he said.
Only a few ferret reintroduction sites remain plague-free so far. They include sites in Kansas and on Rosebud Indian Reservation, Lower Brule Indian Reservation and Wind Cave National Park.
The Fish & Wildlife Service earlier discussed trapping the surviving ferrets and moving them to another site, but moving them now would be difficult because the adult females have recently given birth, Larson said.
The plague can also affect other wildlife, including mountain lions, Larson said.
Meanwhile, signs warning human visitors about the plague have been placed along Highway 44 in Conata Basin and are being placed throughout Badlands National Park.
Visitors have not expressed much concern about the plague so far, according to Atchley and Brian Kenner, chief of the natural resource program in Badlands National Park.
"We don't want to downplay it, but we don't want to cause panic, either," Kenner said.
He said people have been living near prairie dog towns with the plague for more than 50 years in other parts of the West, and it's extremely rare for humans to contract the plague and die.
There have been no cases of the plague reported in humans in South Dakota since the disease was found in western Custer County in 2004.
On the Web:
More information on sylvatic plague can be found at http://www.cdc.gov.
Plague cautions
Visitors to Conata Basin and Badlands National Park are being advised:
* Don't touch dead animals.
* Keep pets in vehicles. Pets, particularly cats, can contract plague from fleas and could potentially transmit it to humans. (Plague may enter a person through a break in the skin by direct contact with tissue or body fluids of a plague-infected animal. Plague can also be transmitted by inhaling infected droplets expelled by coughing by a person or animal, especially domestic cats, with pneumonic plague.)
* Use chemical repellents to prevent flea bites.
Contact Steve Miller at 394-8417 or steve.miller@rapidcityjournal.com
