Plague Survival Genes Found in Prairie Dogs

A study of the genetic basis of plague immunity in prairie dogs has broad implications for conservation. From white-nose syndrome in bats to avian malaria in Hawaiian birds, introduced pathogens are a major cause of population declines in native species. Many prairie dog populations in North America have been nearly wiped out by sylvatic plague, which is caused by the same bacteria that causes the Black Death in humans: Yersinia pestis. Loren Cassin-Sackett and colleagues studied an outbreak of plague in Boulder County, Colorado in 2006–2009 that hit the site of a long-term prairie dog ecology study. The authors trapped and sampled the few prairie dogs that survived, before freeing them. By comparing the whole-genome sequences of seven survivors to sequences from seven prairie dogs who died during the plague, the authors identified genetic variants associated with survivorship. One such gene, Inducible T-Cell Stimulator (ICOS), was also associated with survival in humans during the Black Death in England. Three of the identified genes are also candidate genes for plague resistance in great gerbils. Rapid adaptation to plague is probably multigenic, with a primary role for T-cell related genes. The extent to which the identified variants exist in natural populations is not known, but the results of this study suggests that it may take roughly 25 generations for immunity to evolve. According to the authors, a better understanding of rapid evolution in response to pathogens can help wildlife and ecosystem managers determine when to allow adaptation to proceed on its own and when to try to intervene to prevent extinctions with vaccines, translocations of resistant individuals, or other measures.