from Jean-Marc Duplantier writing in Yersinia: Systems Biology and Control:
Surveillance focuses primarily on human cases, then on vectors and reservoirs, but it is important not to neglect the bacteria (virulence and resistance to antimicrobial agents). Absence of human cases does not mean that plague does not continue to circulate in rodents. Recent re-emergences show the importance of monitoring historic foci considered as extinct. There is a need for surveillance in shantytowns, mines, refugee camps, etc., even far from known foci. It is essential to improve the declaration of human cases. Specific identification of reservoirs is necessary as their sensitivity or resistance to plague varies. Rodent surveillance should be based mainly by estimating their abundance, flea indexes and Yersinia pestis prevalence. Specific identification of fleas is also essential as the different species have not the same transmission efficiency and the same level of resistance to insecticides. Pest control must focus as a priority on the fleas, but it is imperative to combine rodent and flea control. It is preferable to use anticoagulant rodenticides and dust formulations of the insecticides and to focus their application in burrows or bait boxes. As surveillance is costly, determining indicators easy to collect is essential and modeling of long-time series proved that it is possible.
Further reading: Yersinia: Systems Biology and Control