Species composition and plague prevalence in fleas collected from small mammals in mixed grass prairies: Implications for the maintenance of enzootic plague

Maintenance of sylvatic plague (Yersinia pestis) is thought to be inefficient when host mortality rates are high, yet recent findings indicate that low-level enzootic plague can be maintained in susceptible prairie dog populations. An alternative hypothesis for plague maintenance suggests small mammals as an alternative reservoir and that prairie dog colonies exist in a “sea of plague”. Pertinent to this “sea of plague” idea is the concept of bridging vectors allowing the transmission of pathogens within the ecosystem. This would require overlap in flea diversity between small mammals and prairie dogs, or other animals and may challenge the notion of host specificity. This study compares the short grass ecosystem with that of mixed grass prairie, with regard to flea and mammal compositions and plague prevalence in hosts and vectors. Preliminary results show large differences in the flea and mammal composition of the two systems and in overall diversity between the two systems. Moreover, this study demonstrates that although small mammals may not play a large part in interepizootic plague cycling in shortgrass prairie ecosystems, their role in plague maintenance in mixed-grass prairies may be quite different than that of their shortgrass counterparts. Prevalence rates of Y.pestis among fleas and hosts, as well as potential overlap between fleas and hosts, and overall implications for the involvement of small mammals in enzootic plague in mixed grass prairies will be discussed.