A new oral vaccine against sylvatic plague is showing significant promise in the laboratory as a way to protect prairie dogs and may eventually protect endangered black-footed ferrets who now get the disease by eating infected prairie dogs, according to results by a USGS researcher at the USGS National Wildlife Health Center. Sylvatic plague is an infectious bacterial disease usually transmitted from animal to animal by fleas.
This exotic disease is usually deadly for black-footed ferrets and their primary prey, prairie dogs, resulting in local extinctions or regional population reductions. Along with other wild rodents, prairie dogs are also considered a significant reservoir of plague for other wildlife, domestic animals, and people in the western U.S. Prevention of plague in wild rodents by immunization could reduce outbreaks of the disease in animals, thereby reducing the risk for human exposure to the disease.
USGS scientists offered plague vaccine in food for voluntary consumption by 16 black-tailed prairie dogs. They also injected a plague vaccine into 12 other prairie dogs and then studied how much protection against plague the two kinds of vaccines offered. USGS researcher Dr. Tonie Rocke, the lead researcher of the project, found that the prairie dogs that "ate" their vaccine were better protected from the disease than the ones who were injected with a vaccine. These results, said Rocke, demonstrate that oral immunization of prairie dogs against plague provides significant protection from the disease, at least in the laboratory.
Black-footed ferrets, of course, are one of the rarest mammals in North America. An oral vaccine, said Rocke, could be put into bait and delivered into the field without having to handle any animals, a process that is time-consuming, costly, and sometimes stressful for the animals. The same bacterium that affects ferrets, prairie dogs, and other rodents, is also responsible for human cases of plague.
This research was presented at the 58th annual meeting of the Wildlife Disease Association (WDA) held on August 2-7, 2009, in Blaine, Wash.
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