Oral Plague Vaccine Helps Reduce Outbreaks in Prairie Dog Colonies

Prairie dogs in the wild are less likely to succumb to plague after they ingest peanut-butter-flavored bait that contains a vaccine against the disease, according to a U.S. Geological Survey study published today in the journal EcoHealth.

In an effort to increase populations of endangered black-footed ferrets and conserve the prairie dogs they rely on for survival, it is essential for land managers to control outbreaks of the bacterial disease also known as sylvatic plague. The plague affects numerous wild animal species, and domestic animals and humans are susceptible as well.

The vaccine, developed specifically for prairie dogs by scientists at the USGS National Wildlife Health Center and the University of Wisconsin – Madison, elicits a protective immune response that can help them fight off infection upon later exposure to the disease.

“Plague is devastating to prairie dogs, a keystone species of grassland ecosystems,” said Tonie Rocke, a USGS scientist and the project lead. “Our goal in developing an oral plague vaccine is to provide another tool for land managers to reduce the effects of plague outbreaks on prairie dog colonies. This reduction could have positive impacts on conservation of the threatened Utah prairie dog and survival of the endangered black-footed ferret, a prairie dog-dependent species.”

Once thought to be extinct, the black-footed ferret is now one of the most endangered mammals in North America, and plague is a major impediment to its recovery. Both ferrets and prairie dogs are highly susceptible to the disease. The current method for controlling plague consists of dusting prairie dog colonies with insecticide to kill fleas that transmit the pathogen. Although dusting has been effective in controlling the spread of plague, it is labor-intensive, and some flea species may develop resistance to the pesticide.

From 2013 to 2015, a consortium of 14 federal, state, tribal and non-governmental agencies worked together to field test the plague vaccine in all four prairie dog species present across seven western states, including Arizona, Colorado, Montana, South Dakota, Texas, Utah and Wyoming. The study was organized under the Black-footed Ferret Recovery Implementation Team, a multi-agency effort led by the U.S. Fish and Wildlife Service. The study found that prairie dog survival rates were higher on vaccine-treated plots during plague outbreaks compared to plots that received placebo baits, suggesting that consumption of vaccine baits provided protection for prairie dogs.  Researchers anticipate that application of vaccine baits to larger prairie dog complexes on an annual basis will enhance protection against plague.

Colorado Parks and Wildlife conducted the initial field trials that demonstrated vaccine-laden baits could be used safely with no adverse effects for non-target species, such as small mammals, and has been instrumental in furthering large-scale vaccine and bait production for use by managers.  In a companion paper, also published in EcoHealth today (insert link), CPW demonstrated that treating prairie dog colonies annually with a flea control dust or the oral vaccine can prevent population collapse resulting from plague.

“Wildlife managers have struggled to recover ferrets and manage prairie dog colonies due to the devastating effects of plague,” said Dan Tripp, a CPW scientist and a co-author on the USGS study. “It is our hope that use of the sylvatic plague vaccine in select areas, with the support of willing landowners, will help to limit the impact of plague to wildlife.”

Research exploring use of the sylvatic plague vaccine on a broader scale continues with the help of private landowners and tribal, state and federal partners in an effort to promote conservation of grassland habitats and wildlife.

For more information about USGS wildlife disease research, please visit the USGS National Wildlife Health Center website.

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