WGFD Biologist Jesse Boulerice holds ferret during Shirley Basin surveys
Courtesy Virginia Moore
The doctor’s diagnosis was perhaps the most stunning statement Amanda James had ever heard.
It all began October 16, 2015. James left on a hunting trip in Morrow County, Oregon, near Heppener. Five days later, the teenage girl became sick.
On October 24, James was hospitalized in Bend, Oregon. That’s when she heard the news—she had bubonic plague.
Historically, bubonic plague figures as one of the most deadly diseases of all times , nearly wiping out Europe’s population in the mid-1300s. One-third to one-half of Europe, about 75 million people at the time, succumbed to the “black death”, according to Dr. Kenneth Gage, a biologist with the Centers for Disease Control and Prevention specializing in plague research.
“Medieval living conditions…undoubtedly contributed to the spread of the disease as many people lived under crowded conditions in primitive huts that were often shared with livestock and what appears to have been extraordinary numbers of fleas”, said Gage.
The Plague Today
According to the CDC, humans usually contract Bubonic plague after being bitten by an infected flea. Symptoms include fever, headache, chills, muscle pains, weakness and occasionally nausea or diarrhea.
“Patients with bubonic plague will also develop swollen lymph nodes”, Dr. Gage said.
Other forms of plague include Septicemic plague, where the disease spreads to the blood stream, and Pneumonic Plague, which hits the respiratory system and causes symptoms that include shortness of breath and coughing accompanied by a bloody discharge. Pneumonic plague poses a particular danger because it can be spread through inhalation or handling cats with the disease.
While it is possible for a person to get the disease from an infected animal, such cases are rare. People can reduce the risk of exposure by treating their pets for fleas and preventing them from roaming in plague endemic areas.
Today, the medical profession treats the plague with antibiotics, but without prompt treatment, Dr. Gage said, “the disease can cause serious illness or death.”
The Oregon Health Authority reported that Amanda James remained hospitalized during her recovery. No one else was believed to have been affected.
Plague first came to the U.S. around 1900 via rat-infested steamships sailing from Asia and other affected areas.
Today, the majority of plague cases in the U.S. occur in western states due to the high incidence of human-wildlife interactions.
In 1987, “an unusual and apparently unique exposure occurred in Montana when a hunter became infected after handling infected meat from a pronghorn antelope he had shot”, Gage said.
The Black-Footed Ferret
The black-footed ferret’s exposure to plague particularly concerns researchers in Montana and other western states.
One of North America’s rarest mammals, the species was thought to be extinct in the 1970s. According to Pete Gober, the U.S. Fish and Wildlife’s Black-Footed Ferret Recovery Coordinator, “the population was (once) as low as eighteen individuals in northwestern Wyoming.”
Credit 1st from left: Ryan Hagerty, 2nd from left: J. Michael Lockhart
“A farm dog…captured a ferret and that led to the discovery of the last population of ferrets near Meeteetse, Wyoming (in 1981)…They dropped…for a year or two or two until there were around one hundred twenty animals in the wild,” said Gober.
Around 1986, wildlife biologists began establishing captive ferret colonies and a massive recovery effort for the species. Today, ferrets inhabit twenty-eight locations stretching across eight states and parts of Canada and Mexico.
With the exception of Kansas, Gober said plague had spread to all the other sites.
Biologists call the form of plague occurring among ferret populations Sylvatic Plague, meaning it occurs among wild animals, but according to Gober, it’s the same plague bacterium as Bubonic plague.
Plague gets transmitted to ferrets through infected prairie dogs, which the ferrets prey on. Prairie dogs, like other mammals, contract plague from fleas. Researchers used insecticides to limit flea populations among prairie dogs, until they realized, among other things, that fleas had developed an immunity to the insecticides. Recently, a team of scientists came together to develop a plague vaccine for wildlife, a joint effort between the National Wildlife Health Center and the University of Wisconsin. The principal player behind this effort was an NWHC research scientist named Tonie Rocke. During initial field trials of the vaccine, Rocke vaccinated 16 prairie dogs—15 of the prairie dogs survived.
“It looked really good in the lab, so we said, ‘We have to try this in the wild,” Gober said.
The development of an SPV, or Sylvatic Plague Vaccine, as scientists now refer to it, has proven effective in small test locations.
Wildlife biologists now use two types of vaccines in recovery efforts. One is an injectable vaccine administered directly to black-footed ferrets. The other is a baited vaccine for prairie dogs.
Prairie Dog Vaccine Pellets Credit: Conservation Media
Randy Matchett oversees the black-footed ferret recovery efforts at the Charles M. Russell National Wildlife Refuge in Eastern Montana. According to Matchett, the injectable vaccine presents some challenges.
“It’s pretty labor intensive in the wild,” Matchett said.
“For maximum effectiveness and protection, each individual needs to be caught twice about thirty days apart and receive a prime dose, and then thirty days later receive a larger dose.”
Biologists first have to find the ferrets, and since black-footed ferrets are nocturnal, they are identified through spotlighting.
“We drive around in trucks. In some places we’re on foot, and we also use ATV’s. We look for the bright green eye shine. You can see them from quite a ways away with a powerful spotlight. Then we walk to the burrow they are in, and you can see them staring back at you.”
Using wire mesh traps, researchers capture the ferrets, then take them to an on-site processing facility where they are anesthetized. Scientists then implant a subcutaneous chip so the animals can be monitored in the field, and vaccinate them against plague and other viruses.
WGFD biologist Jesse Boulerice processes new ferret during Shirely Basin survey.
Credit: Virginia Moore
According to Matchett, by vaccinating prairie dogs using peanut butter flavored bait, black-footed ferrets are also indirectly treated as the immune response is transferred to the ferrets as well.
U.S. Fish and Wildlife is partnering with other agencies this summer to conduct larger field tests to determine the effectiveness of the oral vaccine. Matchett said distributing the vaccine in larger areas poses another challenge. He told the Pioneer how it works.
“The way we did it in recent years was having people walk following a predetermined line on a GPS unit. Someone would drop baits one at a time, every thirty feet. If you walk fast, the average person can walk maybe 7 or 8 acres an hour. We made this work for a twenty or thirty acre plot, but we had to find a better way for 12-hundred acres or 5-thousand acres.”
Matchett said one of the “better ways” they found was through a mounted triple shooter dispenser he described as “a glorified gum ball machine” that functions similar to the way a softball pitching machine works.
“Think of it this way—what if that same person who was walking a line could now drive an ATV, drop (a bait) straight down, and simultaneously throw another bait thirty feet to the left and another thirty feet to the right. With the same effort, you can now treat three lines at once.”
Matchett said they modified drone software and coupled it with a GPS unit to allow the dispenser to trigger the shooter every thirty feet.
“Now four people can cover fifty or sixty acres in an hour.”
Matchett said the roughness of the terrain is a limiting factor that determines how fast the ATV can be driven. Another method is the use of drones.
“We built a dispenser to fit on a multi-rotor drone. It could only drop one bait at a time, but we programmed it to fly autonomously at points thirty feet apart. We treated 2-hundred acres in an hour.”
The most technologically advanced method for treating plague among ferrets and other wildlife is still in experimental stages. It’s called CRISPR. This is a DNA-based method, focusing on genetic modification of cells.
The story of the black-footed ferret’s rediscovery is the subject of an upcoming documentary entitled, Ferret Town. Virginia Moore, the producer of the film, recalled what attracted her to this story in a conversation with the Pioneer.
“It was a rare opportunity to make a documentary film about an unfolding story, and we were able to capture a historical event.”
The historical event to which Moore refers is the ferrets’ return last summer to the Lazy BV and Pitchfork Ranches in Meeteetse, Wyoming. Not only was this the site where the species was rediscovered, but it was also the 35th anniversary of that rediscovery. Moore believes there is worldwide interest in the story of the black-footed ferret.
“This is one of the best conservation stories in the United States. It’s a really uplifting success story, with a positive message for people.”
Moore said she will be submitting the film for the Jackson Hole Wildlife Film Festival this fall. She hopes Ferret Town will gain nationwide distribution soon.
Note: Amanda James is a pseudonym for the actual Bubonic Plague patient mentioned in this story.