Testing the Generality of a Trophic-cascade Model for Plague

Abstract

Climate may affect the dynamics of infectious diseases by shifting pathogen, vector, or host species abundance, population dynamics, or community interactions. Black-tailed prairie dogs (Cynomys ludovicianus) are highly susceptible to plague, yet little is known about factors that influence the dynamics of plague epizootics in prairie dogs. We investigated temporal patterns of plague occurrence in black-tailed prairie dogs to assess the generality of links between climate and plague occurrence found in previous analyses of human plague cases. We examined long-term data on climate and plague occurrence in prairie dog colonies within two study areas. Multiple regression analyses revealed that plague occurrence in prairie dogs was not associated with climatic variables in our Colorado study area. In contrast, plague occurrence was strongly associated with climatic variables in our Montana study area. The models with most support included a positive association with precipitation in April-July of the previous year, in addition to a positive association with the number of ''warm'' days and a negative association with the number of ''hot'' days in the same year as reported plague events. We conclude that the timing and magnitude of precipitation and temperature may affect plague occurrence in some geographic areas. The best climatic predictors of plague occurrence in prairie dogs within our Montana study area are quite similar to the best climatic predictors of human plague cases in the southwestern United States. This correspondence across regions and species suggests support for a (temperature-modulated) trophic-cascade model for plague, including climatic effects on rodent abundance, flea abundance, and pathogen transmission, at least in regions that experience strong climatic signals.

Nonlinear effect of climate on plague during the third pandemic in China

“…The trophic cascade hypothesis has been tested in studies of C. ludovicianus rodent-host populations of plague in the southwestern United States; the climatic predictors of plague occurrence in the rodents are quite similar to those of human plague cases in the same area. This correspondence provides support for a (temperature-modulated) trophic cascade model for plague (22). In contrast to the studies from North America, however, in Vietnam most human plague cases have been found to occur in dry seasons (23); the risk of plague increased during dry seasons when rainfall was <10 mm (24), showing that the trophic cascade hypothesis may not be generally valid.…”

Landscape and Residential Variables Associated with Plague-Endemic Villages in the West Nile Region of Uganda

“…28,38 It is also believed that areas with increased primary production of food crops, which result from elevated precipitation rates and wetter conditions, may increase the carrying capacity of rodents. 1,2,28,33,35,39,40 After repeating the analysis using only huts that occurred within pixels recently classified as elevated risk (objective 3) ( Tables 5 and 6 ), the association with pigs in the peridomestic setting and distance to neighbor remained as significant predictors of case or control designation.…”

Assessing Human Risk of Exposure to Plague Bacteria in Northwestern Uganda Based on Remotely Sensed Predictors

“…Nonetheless, we believe such an association with agricultural intensity and plague case occurrence is biologically plausible. According to a trophic cascade hypothesis, [35][36][37] areas with increased primary production of food crops may increase the carrying capacity of rodents. Several quantitative models have demonstrated that the probability of plague epizootics, which represent periods when humans are at greatest risk for exposure to infectious fleas, 38 is dependent on reaching critical thresholds of key rodent hosts.…”