New oral vaccine to combat sylvatic plague

A spoonful of sugar helps the medicine go down,” Mary Poppins said.

What about peanut butter?

Rodents such as prairie dogs love peanut butter and black-footed ferrets love prairie dogs, so a peanut butter-like substance has been doctored with an oral vaccine to thwart sylvatic plague.

The new experimental vaccine is added to peanut butter flavored “baits;” little chips of what look like chunks of caramel or peanut brittle.

Wednesday afternoon, the Wyoming Game and Fish Department and Pitchfork Ranch hosted an event to explain field trials of the vaccine where the weasel-like critter was found in the early 1980s.

When sylvatic plague kills prairie dogs it sets off a food-chain chain reaction. Animals like swift foxes, golden eagles and black-footed ferrets prey on prairie dogs for food.

An oral vaccine offers an alternative to time-consuming dusting of prairie dog towns with insecticide to kill the fleas that spread the plague, according to the U.S. Geological Survey.

Game and Fish want support to make it easier for landowners to allow prairie dogs and black-footed ferrets on their property in hopes of expanding the endangered species’ population. 

More than 30 years ago black-footed ferrets were believed extinct, but a colony was discovered on the Pitchfork Ranch. Now the ranch is one of 29 sites hosting field trials to test the vaccine developed by the U.S. Geological Survey, according to Game and Fish.

In 1984, there were 120 ferrets in the Meeteetse area. But, by 1985 canine distemper decimated black-footed ferrets there and sylvatic plague killed most of the prairie dogs. In 1987, the decision was made to catch ferrets in the Meeteetse area and initiate captive breeding in Game and Fish’s Sybille Canyon research facility southwest of Wheatland, said Dennie Hammer, retired Game and Fish education specialist.

The Pitchfork is again playing a central role in the ferrets’ recovery said Renny MacKay, Game and Fish communications director, at a meeting in the Meeteetse Museums prior to the trip to the Pitchfork.   

On Sept. 26, 1981, John Hogg’s dog, Shep, brought a ferret home to the Hogg ranch north of Meeteetse.

In his early days with the Game and Fish, he worked in the Meeteetse area on the ferret capture project, said Scott Talbott, Game and Fish director.

Hammer recalls the ferret discovery and subsequent efforts to capture ferrets that began population recovery efforts. He caught the first ferret in 1981. “That was one of the happiest days of my life,” Hammer said.

TRIALS

From 1999 to 2000 there were plenty of prairie dogs on the Pitchfork, but what was believed to be the sylvatic plague nearly killed off the entire population. However, in recent years the population of white-tailed prairie dogs has grown enormously on the ranch. “They’re definitely increasing,” said Dr. Lenox Baker, one of the Pitchfork owners.

This is the third field season testing the vaccine.

On the Pitchfork, two test plots encompassing 80 total acres are 500 white-tailed prairie dog test subjects eating the pseudo peanut butter, but they don’t seem to mind being guinea pigs.

“They love it,” said Terry Johnson of Endangered Species Advisement, Glendale, Arizona.

Cattle will nibble the bait, but don’t appear overly interested and wild ungulates don’t like it, Johnson said. 

Four years ago Johnson was asked to coordinate the vaccine project, he said.

On each test site there are two 40-acre plots to test the efficacy of the vaccine. One plot at each site uses the vaccine and the other plot has a placebo. It is a blind study, meaning those conducting the field tests don’t know which peanut butter is the vaccine and which is the placebo. Data will be collected from all the sites to appraise the vaccine’s effectiveness. That data will be analyzed in 2017. Tentatively, a vaccine program could begin by 2018 at a cost of $1-2 million to start. Following that, the vaccine could be put to wide use if it proves effective, Johnson said.

The Game and Fish has trapped and ear-tagged 500 prairie dogs on the Pitchfork’s site, said Jesse Boulerice, Game and Fish non-game biologist. They can easily distinguish the dogs eating the peanut butter because a red dye in the bait makes the prairie dogs’ whiskers turn red.

Tonie Rocke, from the University of Wisconsin, Madison, invented the vaccine. She and other collaborators began the vaccine project in 2011. “We think it’s a very, very safe vaccine,” Rocke said.

There are 25 partner organizations in the vaccine effort. The hope is the vaccine will be an aid in the ferret’s recovery, said Mark Sattelberg, U.S. Fish and Wildlife Service field supervisor.

TWO BIT

In a glass cage at the museums, Two Bit regards a crowd gathered round. Two Bit, caught in the Meeteetse area, is short and long, sort of like a small dachshund. From there any comparison to a wiener dog ends. Soft gray and brown fur swaths Two Bit’s tubular body and her ears prickle as though Two Bit knows she is the subject of conversation. Two delightful eyes like polished green emeralds watch the crowd.

Two Bit has delivered several litters, and those kits have been reintroduced into the wild. Every fall 200-250 ferrets are released in 24 reintroduction locations, said Kimberly Fraser, Fish and Wildlife Service education specialist from the National Black-footed Ferret Conservation Center.

Ninety percent of the black-footed ferret’s diet are prairie dogs, Fraser said. Every three days a ferret will seek its preferred prey consuming every morsel, from the prairie dog’s fur to its toenails, Fraser said.

At the Pitchfork test site, curious prairie dogs pop up from their burrows to study the humans.

Prairie dogs tip the scales at up to 3 pounds, but black-footed ferrets weight 1.5 to 2.5 pounds, said Jesse Boulerice, Game and Fish non-game biologist. 

Prairie dogs excavate family burrows with at least two entrances/exits. Ferrets will go after prairie dogs in their holes. The rodent will be on the end of the tunnel kicking dirt behind and the ferret will be pushing the dirt away in hot pursuit, said Lee Tafelmeyer, Game and Fish non-game technician.

COOPERATORS

Landowner cooperation is needed to make the program work, Johnson said.

Under the Endangered Species Act 10(j) section, landowners would not be penalized if a ferret was accidentally killed, MacKay said.

Under a safe harbor agreement for ferrets, landowners would receive financial compensation, Johnson said.

Fish and Wildlife is proposing all of Wyoming as an area for the re-establishment of ferrets under section 10(j). Under 10(j) it must be documented that no black-footed ferrets inhabit Wyoming other than in reintroduction sites. That has been documented, according to Fish and Wildlife.     

CLOSE

“We thank the owners of the Pitchfork Ranch for their support of this project and for all of the partners that are working on behalf of the ferrets,” Talbott said. “If it proves effective, this vaccine has potential to have a positive impact in target situations where we want to help stabilize prairie dog populations and reduce the threat of sylvatic plague.”

The vaccine is important to the ferrets’ population recovery. “Anything we can do to continue to have black-footed ferrets back on the landscape in my opinion is a good thing,” Hammer said.