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Plague vaccine aims to support prairie dog populations

by Wyoming Livestock Roundup

Meeteetse – Black-footed ferrets were thought to be extinct until the 1980s when  ferrets were found outside Meeteetse.

“In 1979, the last Black-footed ferret perished in South Dakota,” said Wyoming Game and Fish Director Scott Talbott. “In 1982, they were found in Meeteetse.”

In 1984, 120 ferrets were located in the Meeteetse area, but canine distemper killed many of them. At the same time, sylvatic plague ran rampant through the white-tailed prairie dog population that provided the ferrets’ main food source.

Talbott noted, “In the mid-1980s, ferrets were taken into captivity, and there is a huge partnership of folks who have worked to help recover the species.”

Retired Wyoming Game and Fish Department Education Specialist Dennie Hammer noted, “Black-footed ferrets are still considered one of the rarest species in all of North America, and it is a tribute to Wyoming and all of the partners over the years that we can say we still have ferrets and the habitat they need to survive.”

On July 8, researchers, wildlife specialists and others gathered at the Pitchfork Ranch outside Meeteetse to hear about the latest developments in the path toward reintroducing Black-footed ferrets.

Researchers and Wyoming Game and Fish Department personnel described a current field trial to combat sylvatic plague that is being conducted at the ranch.

Prairie dog populations

To successfully reintroduce Black-footed ferrets on the landscape, thriving populations of prairie dogs are necessary. However, prairie dogs across the West continue to be decimated by sylvatic plague.

Over the last 15 years, Tonie Rocke of the University of Wisconsin-Madison has worked to develop a vaccine to combat sylvatic plague.

Wyoming Game and Fish Department Public Information Officer Renny McKay noted, “If this vaccine proves to be successful, it can be used in targeted places where we want to reintroduce Black-footed ferrets on the continent.”

Field trials

Over the last three years, Roche’s vaccine has been utilized in field trials across the West.

“Pitchfork Ranch is one of 29 sites that has hosted research on sylvatic plague vaccine,” explained McKay.

In its third season of field trials, many of those involved are optimistic about the potential success of the vaccines.

“Right here on Pitchfork, we have a colony of prairie dogs with two plots that are our study area,” explained Jesse Boulerice, nongame biologist for the Wyoming Game and Fish Department. “Each plot is 40 acres.”

Boulerice continued, “One plot will receive a bait that contains the vaccine for plague, and the other receives a placebo bait.”

The study is blind, meaning that researchers on-the-ground conducting the study do not know which plot is receiving vaccine and which is receiving placebo baits.


The vaccine is delivered in a peanut butter-flavored bait that also has a biomarker to determine whether the prairie dogs have received the vaccine.

“After the animal ingests the biomarker, it marks the hair and whiskers. If we pull a whisker and look at it under ultraviolet light, it fluoresces,” Rocke said.

Prairie dogs are captured and tagged, giving each animal an individual identification. When they are captured, hair and whisker samples are taken, and the prairie dogs are combed for fleas.

“We can send the fleas to the lab to identify the species and see if the flea is carrying plague,” Boulerice said.

The animals are sedated for the process to reduce stress.


Though the study is only three years into a four-year project, Rocke says that preliminary results have shown that 90 percent of prairie dogs are eating the bait.

“We see the biomarker in the hair of almost every prairie dog we capture,” she said. “They eat it readily, and we think that they are getting used to it over time.”

Laboratory trials are also very encouraging, with 95 percent survival rates after a challenge with the oral vaccine after two treatments.

“We don’t know anything about the success rates yet,” Rocke said, “and we won’t know until we get our data in, un-blind the study and look at the data.”

Over the next year, researchers will continue to collect data, hoping for positive results at the end of the study.

“There are a couple of things that are limiting in the recovery of the Black-footed ferret – one being plague that takes over prairie dog town and eliminating the food source for ferrets,” said Mark Sattleberg of U.S. Fish and Wildlife Service. “This vaccine is a hope in the recovery of the Black-footed ferret.”

Saige Albert is managing editor of the Wyoming Livestock Roundup and can be reached at


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