Rodent and Flea Abundance Fail to Predict a Plague Epizootic in Black-Tailed Prairie Dogs

Abstract

Small rodents are purported to be enzootic hosts of Yersinia pestis and may serve as sources of infection to prairie dogs or other epizootic hosts by direct or flea-mediated transmission. Recent research has shown that small rodent species composition and small rodent flea assemblages are influenced by the presence of prairie dogs, with higher relative abundance of both small rodents and fleas at prairie dog colony sites compared to grasslands without prairie dogs. However, it is unclear if increased rodent or flea abundance predisposes prairie dogs to infection with Y. pestis. We tracked rodent and flea occurrence for 3 years at a number of prairie dog colony sites in Boulder County, Colorado, before, during, and after a local plague epizootic to see if high rodent or flea abundance was associated with plague-affected colonies when compared to colonies that escaped infection. We found no difference in preepizootic rodent abundance or flea prevalence or abundance between plague-positive and plague-negative colonies. Further, we saw no significant before-plague=after-plague change in these metrics at either plague-positive or plague-negative sites. We did, however, find that small rodent species assemblages changed in the year following prairie dog die-offs at plague-affected colonies when compared to unaffected colonies. In light of previous research from this system that has shown that landscape features and proximity to recently plagued colonies are significant predictors of plague occurrence in prairie dogs, we suggest that landscape context is more important to local plague occurrence than are characteristics of rodent or flea species assemblages.

A curve of thresholds governs plague epizootics in Central Asia

“…In contrast, a recent study of a relatively small data set on plague in prairie dogs (Cynomys spp.) in North America (Brinkerhoff et al 2010) failed to find any causal association between flea burden and plague outbreaks. This, although, is reasonable for that system, as plague spreads rapidly through prairie dog towns, fleas do not play the same ÔconnectingÕ role between sub-populations, and the role of conventional flea-borne transmission has itself been questioned (Webb et al 2006).…”

“…In contrast, a recent study of a relatively small data set on plague in prairie dogs ( Cynomys spp.) in North America (Brinkerhoff et al. 2010) failed to find any causal association between flea burden and plague outbreaks.…”

Forecasting potential emergence of zoonotic diseases in South‐East Asia: network analysis identifies key rodent hosts

“…), may not always work (Brinkerhoff et al . ). Secondly, new molecular tools and intensive sampling in wild mammal populations have stressed the huge diversity of species that are capable of hosting certain parasites, which renders the concept of ‘reservoirs’ rather ambiguous if not inappropriate.…”

“…landscape modification. First, the 'abundance' paradigm, linking rodent proliferation and high abundance to a high risk of epizootics (Tesago et al 2011;Moore et al 2015), may not always work (Brinkerhoff et al 2010). Secondly, new molecular tools and intensive sampling in wild mammal populations have stressed the huge diversity of species that are capable of hosting certain parasites, which renders the concept of 'reservoirs' rather ambiguous if not inappropriate.…”

Detection of Yersinia pestis DNA in human bubo aspirates in Tanzania

“…From our results, the positive amplicons from rodents and those obtained from human samples obtained during the 2011 outbreak matched, and were all identified as Y. pestis. This suggests the interaction of mammalian reservoirs or flea species and humans in the infectious cycle that lead to humans contacting the disease (Ebright et al, 2003;Brinkerhoff et al, 2010).…”