EID: Plague As a Model for Low Prevalence/epizootic Disease Dynamics

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Outbreaks of infectious diseases in natural populations of plants and animals arise when variation in climate influences density of hosts, contact and disease transmission between hosts, and the size of insect populations that transmit disease. Within these broad patterns, how a disease changes from outbreak conditions to low-level persistence is unknown. Plague, a disease of rodents caused by the bacterium Yersinia pestis, provides an ideal opportunity for studying disease outbreaks interspersed within lulls when disease is almost undetectable. After its introduction into North America, plague has affected most rodent species west of the Great Plains. Black-tailed prairie dogs, burrowing rodents living in social colonies on grasslands, suffer high mortality during outbreaks. Long-term studies in Colorado show that plague outbreaks are more common during El Nino years. This project aims to determine whether plague persists in reservoir hosts (other rodents), remains at low levels within prairie dogs or their fleas, or only moves into grasslands from other habitats following weather-related increases in densities of other rodents. Routes of infection will be studied by trapping rodents and fleas, combined with genetic fingerprinting to identify plague foci. These data will provide values for models that explore disease persistence and transmission. Plague continues to be a human health concern; up to 3,000 worldwide cases are reported yearly. This research provides key information for minimizing disease incidence in the expanding populations of the western US. It is also part of long-term plague surveillance through the Shortgrass Steppe Long-Term Ecological Research project. Students from an urban, ethnically diverse undergraduate institution (Cal-State Fullerton) will gain unique experiences in field ecology, which increases the likelihood they will pursue careers in science.