Black-footed ferrets (Mustela nigripes) require extensive prairie dog colonies (Cynomys spp.) to provide habitat and prey. Epizootic plague kills both prairie dogs and ferrets and is a major factor limiting recovery of the highly endangered ferret. In addition to epizootics, we hypothesized that enzootic plague, that is, presence of disease-causing Yersinia pestis without any noticeable prairie dog die off, may also affect ferret survival…
Vector control improves survival of three species of prairie dogs (Cynomys) in areas considered enzootic for plague
Biggins, D.E., J.L. Godbey, K.L. Gage, L.G. Carter, and J.A. Montenieri
Plague causes periodic epizootics that decimate populations of prairie dogs (PDs) (Cynomys), but the means by which the causative bacterium (Yersinia pestis) persists between epizootics are poorly understood. Plague epizootics in PDs might arise as the result of introductions of Y. pestis from sources outside PD colonies. However, it remains possible that plague persists in PDs during interepizootic periods and is transmitted at low rates among high susceptible individuals within and between their colonies…
A review of plague persistence with special emphasis on fleas
Sylvatic plague is highly prevalent during infrequent epizootics that ravage the landscape of western North America. During these periods, plague dissemination is very efficient. Epizootics end when rodent and flea populations are decimated and vectored transmission declines. A second phase (enzootic plague) ensues when plague is difficult to detect from fleas, hosts or the environment, and presents less of a threat to public health.
Recently, researchers have hypothesized that the bacterium (Yersinia pestis) responsible for plague maintains a continuous state of high virulence and thus only changes in transmission efficiency explain the shift between alternating enzootic and epizootic phases. However, if virulent transmission becomes too inefficient, strong selection might favor an alternate survival strategy. Another plausible non-exclusive hypothesis, best supported from Asian field studies, is that Y. pestis persists (locally) at foci by maintaining a more benign relationship within adapted rodents during the long expanses of time between outbreaks. From this vantage, it can revert to the epizootic (transmission efficient) form. Similarly, in the United States (US), enzootic plague persistence has been proposed to develop sequestered within New World rodent carriers. However, the absence of clear support for rodent carriers in North America has encouraged a broader search for alternative explanations. A telluric plague existence has been proposed. However, the availability of flea life stages and their hosts could critically supplement environmental plague sources, or fleas might directly represent a lowlevel plague reservoir.
Here, we note a potentially pivotal role for fleas. These epizootic plague vectors should be closely studied with newer more exacting methods to determine their potential to serve as participants in or accomplices to a plague persistence reservoir.
Response of mountain plovers to plague-driven dynamics of black-tailed prairie dog colonies